123518886-Femto-Cells

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By utilizing this website and/or documentation, I hereby acknowledge as follows: Effective October 1, 2012, QUALCOMM Incorporated completed a corporate reorganization in

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Variyankandy, Surjit (surjitv) - 12/11/2012 08:56:33 PM PST R

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Released - For Current Employee Use Only

FEMTO DEPLOYMENT

IN UMTS NETWORKS

STUDENT GUIDE

80-W2703-1 REV A


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STUDENT GUIDE

80-W2703-1 REV A


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Material Use Restrictions

These written materials are to be used only in conjunction with the associated instructor-led

class. They are not intended to be used solely as reference material.

No part of these written materials may be used or reproduced in any manner whatsoever

without the written permission of QUALCOMM Incorporated.

Copyright © 2010 QUALCOMM Incorporated.

All rights reserved.

QUALCOMM Incorporated

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This technical data may be subject to U.S. and international export, re-export or transfer

("export") laws. Diversion contrary to U.S. and international law is strictly prohibited.

QUALCOMM is a registered trademark of QUALCOMM Incorporated in the United States and

may be registered in other countries. World Wireless Academy is a trademark of QUALCOMM

Incorporated. WWA and the wwa logo are trademarks of QUALCOMM Incorporated.

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used under license. ARM is a registered trademark of ARM Limited. QDSP is a registered

trademark of QUALCOMM Incorporated in the United States and other countries. Other

product and brand names may be trademarks or registered trademarks of their respective

owners.

Qualcomm Wireless Academy is part of the World Wireless Academy family of training

programs.


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© 2010 QUALCOMM Incorporated MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION

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Table of Contents Section 1: Course Overview ................................................................................. 1-1 Where Can I Learn More? ................................................................................................. 1-2 Introductions ...................................................................................................................... 1-3 Housekeeping ...................................................................................................................... 1-4 Course Goals ...................................................................................................................... 1-5 Course Map and Organization ......................................................................................... 1-7 Course Terminology Legacy and Standard .......................................................................................... 1-8 Macro, Micro, Pico, Femto ................................................................................. 1-9 Access Methods ................................................................................................... 1-10 Hand-in and Hand-out ...................................................................................... 1-11 Section 2: Introduction to Femto ....................................................................... 2-1 Introduction to Femto ........................................................................................................ 2-2 Topics ...................................................................................................................... 2-3 Femto Expectations ............................................................................................................. 2-4 Femto Deployments ............................................................................................................ 2-5 Residential versus Enterprise Multi-Femto Networks ......................................... 2-6 What is a Femto Cell?.......................................................................................................... 2-7 Femto Coverage and Quality ........................................................................................... 2-8 Estimating Femto Coverage and Quality .................................................................... 2-9 Capacity of a Femto CS .................................................................................................................... 2-10 HS .................................................................................................................... 2-11 How does a Femto interact with the Macro network? ........................................ 2-12 Topics .................................................................................................................... 2-13 Femto Deployment Strategies....................................................................................... 2-14 Deployment Strategies Open Access .......................................................................................................... 2-15 Closed Access ....................................................................................................... 2-16 Hybrid Access....................................................................................................... 2-17 Spectrum Usage................................................................................................... 2-18 Topics .................................................................................................................... 2-19 Common Concerns with Femto Deployments ........................................................ 2-20 Where do we go from here? ........................................................................................... 2-21 Section 3: Femto Network Overview ................................................................ 3-1 Femto Network Overview ................................................................................................ 3-2 Objectives ...................................................................................................................... 3-3 Femto Network Layout ...................................................................................................... 3-4 Femto Functionality ............................................................................................................ 3-5 HMS, SeGW, HNB GW Functionalities .......................................................................... 3-6 Femto Configuration — Before Making a Call .......................................................... 3-7 Femto Self Configuration — When? ............................................................................. 3-8 Femto Self Configuration — How? ................................................................................ 3-9 Where do we go from here? ........................................................................................... 3-10


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Section 4: Preparing the Network for Femto Deployment ....................... 4-1 Preparing the Macro Network ........................................................................................ 4-2 Objectives ...................................................................................................................... 4-3 Femto Spectrum Allocation ............................................................................................. 4-4 Femto Frequency Allocation ........................................................................................... 4-5 Dedicated and Shared Spectrum Alternatives ......................................................... 4-6 Deploying Femtos on GSM-TCH spectrum................................................................. 4-7 Example of Interference: Macro UMTS vs. GSM -TCH ............................................ 4-8 Guidelines for Shared Spectrum Deployment .......................................................... 4-9 Femto Deployment with 4+ Carriers ......................................................................... 4-10 Solution 1: .............................................................................................................. 4-11 Solution 2: .............................................................................................................. 4-12 Femto PSC Assignment and Updating Macro C onfiguration ............................ 4-13 How many PSCs to use for Femtos? ............................................................................ 4-14 Which PSCs to set aside for Femtos? .......................................................................... 4-15 PSC Planning / Re-planning in Macro Network..................................................... 4-16 Macro Neighbor List Modifications ............................................................................ 4-17 Macro Neighbor List Sizes, Intra - versus Inter-Frequency ............................... 4-18 Idle Mode Neighbor List Constraints: SIB11 Overflow ....................................... 4-19 SIB11 Size Estimation ...................................................................................................... 4-20 Answer: SIB11 Size Estimation .................................................................................... 4-21 Femto Neighbor List Setting .......................................................................................... 4-22 Femto LAC and PLMN-ID Assignment ....................................................................... 4-23 How many LACs to Reserve for Femto? .................................................................... 4-24 Access Control with today’s Femto Network .......................................................... 4-25 LAC-based Access Control with Legacy UEs .......................................................... 4-26 Which PLMN-ID to Assign to Femto ? ........................................................................ 4-27 Where do we go from here? ........................................................................................... 4-28 Section 5: Parameter Settings for Legacy UEs and Networks .................. 5-1 Macro and Femto Parameter Settings ......................................................................... 5-2 Objectives ...................................................................................................................... 5-3 Mobility between Macro and Femto ............................................................................ 5-4 Search and Reselection Strategies ............................................................................... 5-5 Legacy Cell Reselection Aspects with Femtos .......................................................... 5-6 Femto Discovery and Reselection Strategies ............................................................ 5-7 Best Coverage vs. Femto Priority — Parameter Strategies ................................ 5-8 Cell Reselection vs. Open/Closed Access .................................................................... 5-9 Measurement and Reselection Rules ......................................................................... 5-10 Legacy Measurements Rules (non-HCS) ................................................................. 5-11 Legacy Cell Ranking and Reselection Rules (non -HCS) ...................................... 5-12 Hierarchical Cell Structure (HCS) — Main Concepts ........................................... 5-13 Legacy Measurements Rules (HCS) ........................................................................... 5-14 Legacy Cell Ranking and Reselection Rules (HCS) ............................................... 5-15 Best Coverage .................................................................................................................... 5-16 Search/Reselection Parameters — Best Coverage .............................................. 5-17 Prioritizing Femto: Non-HCS ........................................................................................ 5-18 Prioritizing Femto Selection — non-HCS ................................................................ 5-19


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Femto Priority Macro Settings: Shared Carrier ................................................................... 5-20 Femto Setting: Shared Carrier ..................................................................... 5-21 Macro Settings: Dedicated Carriers ........................................................... 5-22 Femto Settings: Dedicated Carriers ........................................................... 5-23 Macro Settings: Multi-Carrier ....................................................................... 5-24 Femto Settings: Multi-Carrier ...................................................................... 5-25 Prioritizing Femto: HCS ................................................................................................... 5-26 HCS Configuration for Prioritizing Femto ............................................................... 5-27 Femto Priority Macro Settings: Shared Carrier .................................................................... 5-28 Macro Settings: Shared Carrier .................................................................... 5-29 Macro Settings: Dedicated Carrier ............................................................. 5-30 Macro Settings: Dedicated Carrier ............................................................. 5-31 Macro Settings: Multi-Carrier ....................................................................... 5-32 Macro Settings: Multi-Carrier ....................................................................... 5-33 HCS vs. non-HCS .................................................................................................. 5-34 Section Overview — Parameter Settings ................................................................. 5-35 HCS vs. non-HCS Parameters Quiz .................................................................................................................... 5-36 Answers .................................................................................................................. 5-37 Quiz .................................................................................................................... 5-38 Answers .................................................................................................................. 5-39 Quiz .................................................................................................................... 5-40 Answers .................................................................................................................. 5-41 Section Overview — Parameter Settings ................................................................. 5-42 Femto Handover Procedures ........................................................................................ 5-43 Inter-RNC Hard Handover: Intra-MSC/SGSN ......................................................... 5-44 Inter-RNC Hard Handover: Intra-SGSN Forward HO .......................................... 5-45 Femto Hand-in Issues ....................................................................................................... 5-46 Femto Hand-in Feasibility .............................................................................................. 5-47 Femto Hand-out Aspects ................................................................................................. 5-48 Femto Hand-out Events ................................................................................................... 5-49 Intra-frequency MAHO — Example of RRC Signaling ......................................... 5-50 Inter-frequency MAHO — Example of RRC Signaling ......................................... 5-51 Inter-RAT MAHO — Example of RRC Signaling ..................................................... 5-52 Hand-out Parameters Quiz .................................................................................................................... 5-53 Answers .................................................................................................................. 5-54 Where do we go from here? ........................................................................................... 5-55 Section 6: Femto Optimization Mechanisms ................................................. 6-1 Femto Optimization ............................................................................................................ 6-2 Objectives ...................................................................................................................... 6-3 Femto Optimization Mechanisms .................................................................................. 6-4 Interference Management Optimization .................................................................... 6-5 Network Listen based Tx Power Calibration ............................................................ 6-6 Mobile Assisted Range Tuning ........................................................................................ 6-7


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Guest Mobile Protection .................................................................................................... 6-8 Home Mobile Protection ................................................................................................... 6-9 Mobility Management Optimization .......................................................................... 6-10 Femto Discovery Issues ................................................................................................... 6-11 Femto Discovery via Beacons ....................................................................................... 6-12 Active Hand-in (Mobile Sensing) ................................................................................. 6-13 Service Quality Optimization ......................................................................................... 6-14 Femto Tx Diversity ............................................................................................................ 6-15 Uplink Throughput Enhancers ..................................................................................... 6-16 Where do we go from here? ........................................................................................... 6-17 Section 7: Femto Standard Evolution ............................................................... 7-1 Femto Standard Evolution................................................................................................ 7-2 Objectives ...................................................................................................................... 7-3 3GPP standards — Rel 8 and Beyond: Summary .................................................... 7-4 Standard Femto Definitions ............................................................................................. 7-5 3GPP Rel 8 Enhancements................................................................................................ 7-6 Standardized Network Architecture ............................................................................ 7-7 Standard Femto Architecture ......................................................................................... 7-8 New Femto Protocols over Iuh ....................................................................................... 7-9 Closed Subscriber Group ................................................................................................. 7-10 CSG — Closed Subscriber Group .................................................................................. 7-11 CSG vs. Legacy Closed Access ........................................................................................ 7-12 User CSG Allowed List in the UE .................................................................................. 7-14 User CSG Allowed List in the Network ...................................................................... 7-15 CSG Access Control in the Network ............................................................................ 7-16 Femtos can broadcast new parameters .................................................................... 7-17 CSG Cell Reselection — New Broadcast Information .......................................... 7-18 CSG (Re)selection Procedures ...................................................................................... 7-19 Femto Characteristic ......................................................................................................... 7-21 Femto RF Characteristics ................................................................................................ 7-22 3GPP Rel 9 Enhancements.............................................................................................. 7-23 Hybrid Femtos .................................................................................................................... 7-24 Hand-In .................................................................................................................... 7-26 Femto Hand-in .................................................................................................................... 7-27 Intra-frequency Femto Hand-in Signaling Flow .................................................... 7-28 Inter-frequency/RAT Femto Hand-in Signaling Flow ......................................... 7-29 Other Rel 9 Enhancements ............................................................................................. 7-30 Operator CSG Allowed List ............................................................................................. 7-31 Manual CSG selection and Temporary CSG membership .................................. 7-32 Summary – What have we learned? ........................................................................... 7-33 Section 8: Appendices ............................................................................................ 8-1 Appendix A: 3GPP Idle Mode Procedures ....................................................... 8-2 3GPP Idle Mode Procedures — Major Enhancements .......................... 8-3 PLMN Selection — Major Enhancements ................................................... 8-4 Cell (Re)selection — Major Enhancements ............................................... 8-5


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Appendix B: 3GPP Rel 8 Femto Service Requirements .............................. 8-7 General Femto Service Requirements ......................................................... 8-8 Femto Installation Requirements .................................................................. 8-9 Femto Identification & Display Requirements ....................................... 8-10 Femto Mobility Requirements ...................................................................... 8-11 Femto Manual Selection Requirements .................................................... 8-12 Femto Access Control Requirements ......................................................... 8-13 Appendix C: 3GPP Rel 8 CSG based Access Control Procedures .......... 8-14 UE Registration for CSG UEs and CSG Femtos ........................................ 8-15 UE Registration for non-CSG UEs or non-CSG Femtos ........................ 8-16 Appendix D: 3GPP Reference Specifications .............................................. 8-17 3GPP Specifications for Femto Enhancements: Rel 8 .......................... 8-18 3GPP Specifications for Femto Enhancements: Rel 9 .......................... 8-20


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Acronyms and Abbreviations 3GPP 3rd Generation Partnership Project 64-QAM 64-Quadrature Amplitude Modulation ACL Access Control List ACS Adjacent Channel Selectivity ADSL Asymmetric Digital Subscriber Line AS Access Stratum ASET Active Set AUTN Authentication Token BCCH Broadcast Control Channel BCH Broadcast Channel BS Base Station BSA Base Station Almanac BSIC Base Station Identification Code CIO Cell Individual Offset CM Compressed Mode CN Core Network CPICH Common Pilot Channel CR Change Request CS Circuit Switched CSG Closed Subscriber Group DAHO Database Assisted Handover dB Decibel dBm Decibel referenced to 1 milliwatt DC-HSPA Dual Cell HSPA DCH Dedicated Channel DDF Device Description Framework DL Downlink DM Device Management DSL Digital Subscriber Line EPLMN Equivalent Public Land Mobile Network FACH Forward Access Channel FDD Frequency Division Duplex Femto Femto cell/Base Station GPRS General Packet Radio Service GPS Global Positioning System GSM Global System for Mobiles GTP-U GPRS Tunneling Protocol - User Plane H(e)NB Home Enhanced Node B HCS Hierarchical Cell Structures HHO Hard HandOff HLR Home Location Register HMS Home Management System HNB-GW Home Node B Gateway HNB Home Node B HNBAP Home Node B Application Part HPLMN Home Public Land Mobile Network HS High Speed


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HSDPA High Speed Downlink Packet Access HSPA High Speed Packet Access HSPA+ Evolved High Speed Packet Access HSS Home Subscriber Server HSUPA High Speed Uplink Packet Access HUE Home User Equipment IANA Internet Assigned Numbers Authority ([email protected]) ID Identification IE Information Element IFHO Inter-Frequency Handover IMSI International Mobile Subscriber Identity IOT Interoperability IP Internet Protocol IRAT Inter-Radio Access Technology IRAT HO Inter-Radio Access Technology Handover ISDN Integrated Services Digital Network ISUP ISDN User Part KHz Kilo HertZ LAC Location Area Code LAI PLMN ID + LAC LBHO Load Based Handover LBS Local-Based Service LIPA Local IP Access MAHO Mobile Assisted Handover (also called QBHO) MAP Maximal Apriori Decoder MBMS Multimedia Broadcast/Multicast Service Mbps Megabits Per Second ME Mobile Equipment MHz Mega Hertz (unit of frequency, 1,000,000 cycles per second) MIMO Multiple Input Multiple Output MM Mobility Management MO Mobile Originated; Managed Object MS Mobile Station MSC Mobile Switching Center MT Mobile Terminated MUE Macro User Equipment NAS Network Access Server NL Network Listen NR Noise Rise OAM Operation Administration and Maintenance O&M Operation and Maintenance OMA Open Mobile Alliance OOS Out of Service OTA Over-the-Air PCH Paging Channel (Transport Channel) PCR Physical Channel Reconfiguration PL Physical Layer


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PLMN Public Land Mobile Network PPI Payload Protocol Identifier PS Packet Switched PSC Primary Scrambling Codes QBHO Quality Based Handover (also called MAHO) QoS Quality Of Service RAB Radio Access Bearer; Reverse Activity Bit RAN Radio Access Network RANAP Radio Access Network Application Part RANAP Radio Access Network Application Part RF Radio Frequency RL Reverse Link RNC Radio Network Controller RoT Rise Over Thermal RPLMN Registered Public Land Mobile Network RRC Radio Resource Control RSCP Received Signal Code Power RSCP Received Signal Code Power RSSI Received Signal Strength Indicator RTCP Real-time Transport Control Protocol RTP Real Time Protocol RUA RANAP User Adapation Rx Receive SBHO Service Based Handover SCTP Stream Control Transmission Protocol SeGW Security Gateway SGSN Serving GPRS Support Node SHO Soft Handoff SI Scheduling Information SIB System Information Block SINR Signal-to-Interference-plus-Noise Ratio SLA Synchronous Line Adapter SOHO Small Office, Home Office SRNC Serving Radio Network Controller; Signaling Radio Network Controller SRNS Serving Radio Network System TCH Traffic Channel TR-069 Technical Report 069 defines an application layer protocol for remote management of end-user devices. Tx Transmit UARFCN UTRA Absolute Radio Frequency Channel Number UE User Equipment UL Uplink UMTS Universal Mobile Telecommunications Systems URA UTRAN Registration Area USIM Universal Subscriber Identity Module UTF Unicode Transformation Format UTRA Universal Terrestrial Radio Access UTRAN Universal Terrestrial Radio Access Network VLR Visitor Location Register VPLMN Visited Public Land Mobile Network


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WCDMA Wideband Code Division Multiple Access


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Femto Deployment in UMTS Networks

Section 1: Course Overview

80-W2703-1 Rev A

1-1© 2010 QUALCOMM Incorporated MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATION

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HNB and HeNB

Because this training focuses on UMTS, only the HNB (or Femto) is considered, even in the context of Rel 8 and beyond. In Rel 8 and beyond, Home evolved Node B (HeNB) is also defined, but HeNB only applies to LTE.


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Micro/Pico/Femto

The distinction between Micro and Pico is not formal, but a Pico cell is expected to provide limited coverage and lower capacity. In practical terms, the difference can also be seen in the deployment scenario of each: a Micro cell may be deployed outdoors below clutter height (typical antenna height is 3 to 8 meters), or indoors in large buildings (shopping mall, airport, etc.). A Pico cell would be deployed in smaller spaces such as a shop or a small transportation hub. In that respect, a Pico cell would have similar deployment usage as an enterprise Femto.

Femto cells, when applied in residential deployments, have a footprint even smaller than the Pico, typically per one house or apartment.

MAY CONTAIN U.S. AND INTERNATIONAL EXPORT CONTROLLED INFORMATIONSection 1-8

Macro: Provides wide area coverage from hundreds of square meters to a few square kilometers

Micro: Localized outdoor coverage from tens to hundreds of square meters, large indoor space (mall, airport…)

Pico: Localized coverage, e.g., an office. Similar coverage goal as Enterprise Femto

Femto: Personal coverage, e.g., residential or SOHO (Small Office, Home Office)

Course Terminology: Macro, Micro, Pico, Femto


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Soft handoff not expected to be supported between Macro and Femto, or Femto to Femto

Hand-in: • Hard handoff toward the Femto

• Source can be any of Macro, Micro, Pico, Femto…

Hand-out:• Hard handoff from the Femto

• Source can be any of Macro, Micro, Pico, Femto…

Course Terminology: Hand-in and Hand-out

Macro, Micro, Pico, Femto…


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Improving Indoor Coverage

• Most calls are made indoors

• Building Macro sites is costly and time consuming

• Covering indoor users from Macro sites is inefficient because the signal is attenuated by the building

Free up Capacity From Macro Sites

• Transport network costs become significant as data traffic increases

Pave the Way for New Cool Features or Call Plans

• Location based services (know when children/spouse arrive home)

• All-you-can-eat plans for voice and data


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2009:

Residential deployment

2010:

Expanding residential deployment

Trial of enterprise deployment

Next:

Enterprise deployment

Evolution toward Pico deployment

Femto Deployments

DenseDeployments

OutdoorDeployments

ResidentialFemto networks, e.g., Malls, Venues, etc.

Large Enterprises

Small EnterprisesHome offices

Open AccessHot Spots

Initial Femto deployments target Residential, then Small Enterprise/Home office


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Residential and Enterprise Femto

From a specification point of view, Residential and Enterprise Femtos are expected to be similar. From an architecture point of view, in particular at the Gateway level, Enterprise architecture will need to evolve to ensure that handoff between Femtos is supported.


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Transmit Power for the Femto

The standard (25.820) currently recommends that the maximum power for a Femto be limited to + 20 dBm. This value is defined to ensure that radiation exposure is limited to 1mW/cm2 at a distance of 20 cm. Note that radiation exposure varies based on the frequency.

The minimum transmit power is not directly defined, but the signaled CPICH power (in SIB 5, refer to 25.331) is limited to – 10 dBm, thus indirectly limiting the minimum Tx power.

Regulatory Limitations

Femto deployment will be impacted by regulations in different places in different countries. For example:

• Private usage of a public resource (spectrum): In the Closed Subscriber Group mode of operation, Femto can be considered private usage of a public resource (spectrum).

• Public usage of a private resource (ADSL: Asymmetric Digital Subscriber Line): With open deployment operation, the backhaul (ADSL) will be used to send public, rather than private, data. Such usage of the ADSL may be limited by subscriber agreement or by regulation.

• Emergency calls: To ensure that emergency calls can be accurately located, a call on a Femtoshould be referenced to a street address or the Femto position should be reflected in the Base Station Almanac (BSA) of the Location Based Service (LBS). To address this limitation, a GPS receiver can be included in the Femto.

• Radiation within the licensed area: As with any network operator equipment, a Femto should be allowed to radiate only in the operator’s licensed area. This is particularly critical if the Femto is located close to a license boundary. When a GPS receiver is implemented in the Femto, self-configuration can consider the actual Femto location to ensure compliance with license requirements.


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Femto Coverage

Considering the limited transmit power of a Femto, coverage provided by a Femto varies in different suburban deployment scenarios. The coverage presented in this example (i.e., Ec/No) represents the coverage observed by the user. In Example 1, the perceived coverage is larger, mainly due to the lower Macro signal level observed in that case. In Example 2, the Macro coverage is stronger, resulting in smaller coverage for the Femto.


Femto Coverage and Quality

• With the available transmit power, Femto signal strength is sufficient to provide coverage in one typical residential home.

• Femto signal quality would depend on the surrouding Macro signal.

FemtoX

x

Highlighted area shows Femto coverage areaExample 1

Example 2


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Femto Coverage, Ec/No

As illustrated in the previous slide, Femto Ec/No coverage directly depends on the signal level present on that carrier before Femto deployment. This can be estimated using a simple propagation model and a set Ec/No threshold for the Femto.

Femto Coverage, RSCP

In addition to the Femto Ec/No variation, RSCP would also vary with distance (not shown here). This coverage limit directly depends on the Femto CPICH power (Femto Qrxlevmin), the operating frequency, and the number of walls. Based on these variables, the Femto coverage would be between 20 m and 100 m.


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Femto Capacity

Current Femtos are typically limited to 4 concurrent channels, with planned evolution to 8, then 16. From this, the number of supported subscribers will directly depend on the expected traffic per subscriber and the expected grade of service (GoS). Using the Erlang B theory and assuming 2% Grade of Service, the table shows the expected number of supported subscribers for different numbers of available channels. This example defines a channel as an entity capable of supporting one user at a given time, similar to the concept of Channel Element used in Macro Node B.

The example represents the number of supported subscribers based on Erlang theory. The number of subscribers connected to a given Femto may be further limited by vendor implementation, e.g., the maximum number of concurrent (active) users will be limited to the number of channel elements available for traffic.

Concurrent users

The concept of concurrent users is more applicable to CS or DCH-based PS, rather than HS. For HS, it is expected that A-DPCH (associated DPCHs used for SRB and/or power control) would consume one resource at the Femto, thus effectively limiting the number of HS users in cell_DCH. For non-dedicated connected mode (cell_FACH and the like), limitations on concurrent users will be different.


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HS Capacity

HSPA throughput will mostly depend on the HS capabilities of the Femto and the UE (HS category, HOM, or MIMO support) and backhaul capacity.

Associated DPCHs are those used for SRB and/or power control.

Note: Rel 8 HSPA+ upper range for Downlink peak rates (42 Mbps) assumes 64-QAM and 2x2 MIMO in 5 MHz or 64-QAM and Dual Carrier (DC)-HSPA (10 MHz). Rel 9 HSPA would allow doubled rates of up to 84 Mbps for the Downlink and 21 Mbps for the Uplink.


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Mobility and LAC

Considering the limitation of Rel 7 and below, LAC in a Femto network would be used to manage access of the UE white list. With this usage of LAC, it is recommended to assign as many LACs to a Femto as possible, as discussed in Section 5.

The concept of white list refers to UEs that are allowed to access one given Femto, in the case of Closed Subscriber Group (defined later in this section).


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UE Unavailability and Signaling Load

In the current Femto implementation, we need to assume that the Femtos are always in a specific LAC. Otherwise all paging of UEs located in the (non-specific) LAC would need to go to the Femto, which may have a detrimental impact on ADLS loading.

The impact of having a Femto on a specific LAC is that each time a UE moves in or out of the Femto coverage area, a registration update must take place to ensure efficient paging. As for any transition, during the registration update, the UE is not reachable by the network from the moment it starts to camp on the new LAC until the moment the LAU is completed.


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Interference Management

Interference management, as described in Section 6, provides protection for both the Macro and Femto users, and should always be considered, starting with Femto Self Configuration.

Femto in Network with 4 Carriers or More

In a network with 4 or more carriers, irrespective of the Femto carrier assignment, the limitation of the standard must be taken into account. In particular, the standard clearly specifies UE behavior for handling 2 additional carriers in the Neighbor List, but does not specify the expected behavior when 3 (or more) neighboring frequencies are defined. Section 4 provides recommendations for Neighbor List assignment for this scenario.

Additional Configurations

The three typical configurations presented here can be further combined to address more possible configurations. For example, the dedicated + shared carrier configuration can be used for more or fewer carriers. Similarly, the setting provided for the single shared carrier could be used for the multiple shared carrier, without a dedicated carrier.

Dedicated Macro Carrier and Shared Carrier

Initially, it is expected that Femto would be deployed on a single shared carrier. With a high concentration of Femtos, it may be advantageous to allow Femtos on multiple carriers to mitigate possible Femto-to-Femto interference.


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Interference and Interference Management

In the current standard (Release 7 or earlier), interference management is not considered. In future standard releases, interference management is only partly addressed. Interference management is expected to be addressed initially through proprietary implementations (as mentioned in Section 6).

Rel 8 Improvement

In addition to defining Femto architecture, Rel 8 introduces the concept of Closed Subscriber Group. CSG improves UE stand-by time by enabling the UE to optimize its searches and its registration attempts. More details are provided in Section 7.


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Comments/Notes


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Section 3: Femto Network Overview

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Proprietary versus Standard Architecture

Femto networks were initially deployed considering proprietary interfaces, mainly between the Femto and the Gateway, and between the Gateway (or Femto) and the HNB Management System (HMS). As the industry is adopting Femto, the architecture tends toward standardization.

With Femto architecture standardization, Interoperability (IOT) between the different Femtonetwork nodes is also expected. Currently, the Femto Forum (www.Femtoforum.org) is coordinating the IOT efforts for Femto (or Home Node B, HNB).

The diagram above depicts an architecture that is fairly close to the standard one (Iu+ is called Iuh in Rel 8, see Section 7 for more details), focusing on the basic/main entities needed to make Femtosoperational.

In the pre-standard architecture, the OAM connection between the Femto and the Management System is left to vendor implementation. In the Rel 8 standard implementation , the OAM would use TR-069 format.


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Femto Functionality

Conceptually, Femtos include both Node B and RNC functionality in a single entity. However, considering the different protocol layers, Femtos do not include all the RNC functionalities. In particular, Femtos do not include the necessary interconnections, which are handled by the FemtoGateway.


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Femto Network Nodes Functionalities

More details on node functionality are provided in the standard (notably 25.467), at the FemtoForum (www.Femtoforum.org), or in vendor documents. Only the critical functionalities are described in this section.

For proprietary implementations, the functionalities per node may be slightly different, but would achieve similar results.


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Femto Network Node Basic Functionalities

Based on the current standard (25.467 and 25.469), the different nodes are used to:

• Provision the Femto: A Femto needs to communicate with the HMS to obtain the initial parameters, or the parameters required for self configuration. Provisioning includes setting different groups of parameters: CN parameters, RAN parameters, and RF parameters.

• Connect to the appropriate HNB-GW: During configuration, the Femto also obtains the necessary information to connect to the appropriate gateway. This connection will typically go through a Security Gateway to ensure the confidentiality of the information transfer. This Security Gateway may be included in the HNB-GW or can be a separate node.

• Discover and Register to the HNB-GW: Discovery of the HNB-GW is supported by the HMS. At the conclusion of the registration process, the Femto is known to the network and is ready to radiate.

White List Configuration

Based on the current standard, the white list and related access control can be handled either by the HNB-GW or the Femto itself.


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Self Configuration of the Femto

For most of these steps, the Femto location must be known. This ensures that the interaction with the Macro will be as efficient as possible. In particular, this ensures that the Femto is radiating on a frequency that is licensed by the operator. This will also ensure that the Macro network can instruct the UE to search for and discover the Femto.

The standard recognizes three main methods to geo-locate the Femto:

• Based on internal geo-location capabilities (GPS receiver)

• Based on IP address

• Based on RF fingerprint. This fingerprint is determined by listening to the Macro network, either GSM or UMTS.

The information gathered during this process typically is also used to generate the Neighbor List.

Only the main parameters are included here. TR-069 and WT-196 from the Broadband Forum provide a complete list of the parameters that can be set, read, or self configured for a Femto (see http://www.broadband-forum.org/technical/technicalwip.php ).


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Spectrum Allocation

Femtos can be configured anywhere within the licensed spectrum. Ultimately, the spectrum allocation should be selected to minimize interference and ensure that Femto discovery is not impacted. Both points will be considered in this section.


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Partial Overlap

In the partial overlap case, a different UARFCN is used for Femto and Macro, even if the spectrum is actually shared. This can be achieved by using a UARFCN that is off by 1 (or a few) channels (a channel is 200 kHz). With partial overlap, the Macro to Femto interference is similar, but searches are done as inter-frequency rather than intra-frequency. The main expected benefits of this arrangement are:

• PSC assignment flexibility, because effectively a new frequency is used, thus the Femto PSC could be selected within the entire PSC space.

• Neighbor List flexibility, because inter-frequency Neighbor Lists are typically less used than intra-frequency, thus all Femto PSCs can be added to the NL.


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GSM Spectrum and Interference

When deploying Femto on GSM spectrum, the interference over the 5 MHz UMTS signal is not constant, it changes based on the GSM-TCH assigned, in increments of 200 kHz.


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UMTS and GSM Interference

The above figure illustrates data collected in an area where both UMTS and GSM cells are present.

The average UMTS level is around 8 to 10 dB higher on 850 MHz compared to 1900 MHz, and UMTS850 is on average 10 to ~12 dB higher than GSM.

On either UMTS 850 or 1900, 10 dB spikes are observed, likely due to HSDPA.

Large time variations in interference from GSM-TCH, both long term average (load dependence) and short term burstiness (frequency hopping).


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Femto on One or Several Macro Carriers?

To ensure that one Macro carrier is free of Femto interference, and thus free from potential outage, Femtos should not be deployed on all the Macro carriers. If more than two carriers are used for Macro, the next question is whether a Femto needs to be deployed on more than one Macro carrier.

Deploying Femtos on more than one carrier has the advantage of limiting Femto-to-Femtointerference, because the adjacent Femto could use a different carrier. This would be ideal for an apartment complex. This type of multicarrier Femto deployment also has some limitations. In particular, this would require all the Femto carriers to be defined on each carrier Neighbor List, to ensure efficient discovery of the Femto.


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Femto Deployment with 4+ Carriers

The following slides describe two alterantive solutions to address both challenges above.


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PSC Limitations and Multi-carrier

Even when a Femto is deployed on a dedicated carrier, only a limited number of PSCs can be allocated for the Femto. This limitation is not due to the maximum number of neighbors per carrier (32); it is due to the maximum number of neighbors based on the SIB11 size limitation (this is explained later in this section).


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Selecting PSCs for Femto

The first step to determine which PSCs to use for Femto is to review the current PSC allocation to identify the lesser used PSCs. These PSCs should be the preferred PSCs to use for Femto, because this would minimize the PSC replanning effort.

During PSC replanning, a PSC planning strategy should be defined, as illustrated on the next page.


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Intra- and Inter-frequency Neighbor Lists

Typically, intra-frequency Neighbor Lists are longer than inter-frequency Neighbor Lists. This is mainly due to two reasons:

• Use of neighbor recommendation tools: These tools collect statistics on detected sets to make recommendations on the Neighbor List. During Compressed mode, searching and reporting can be optimized by measuring only the monitored set cells; this limits the opportunity to recommend neighbor additions.

• Missing neighbors causing dropped calls: Missing intra-frequency neighbors may cause dropped calls, because the missing neighbor is seen as interference. For inter-frequency, a missing neighbor will not be considered interference; instead, it would prevent the target cell from being measured.

For these reasons, the inter-frequency Neighbor List is likely to be shorter. Therefore, it would be easier to add Femto PSCs to this list while keeping the list below 32 entries. If Femtos are deployed on a dedicated carrier, the issue is minimized even more because any PSC could be used.


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SIB11 Size and Number of Neighbors

The standard specifies independently the maximum size of SIB11 and the number of neighbors that a UE should be able to monitor. Effectively, SIB11 cannot accommodate a total of 96 neighbors, but the flexibility to fill the NL is left to the operator, depending on the network configuration.

Accurate SIB11 size estimation would require knowledge of which optional Information Element (IE) is transmitted. In the absence of such detailed information, an estimation can be done assuming:

• Intra-frequency neighbor requires 2 bytes

• Inter-frequency neighbor requires 6 bytes

• IRAT neighbor requires 5 bytes

• Neighbor specific Qqualmin, Qrxlevmin, or Qoffset requires 1 byte each

• SIB11 total size is 444 bytes


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Reminder




• Neighbor specific Qqualmin, Qrxlevmin, or Qoffset require 1 byte each



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• Neighbor specific Qqualmin, Qrxlevmin, or Qoffset require 1 byte each



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LAC Challenges

From 3GPP specification (24.008), a UE that received a Registration Reject from a given LAC must forbid that LAC for 12 or 24 hours (or until power cycle). This mechanism is typically used for admission control in case of closed access. However, this could cause issues if a given UE detects two Femtos with the same LAC, one for which it is white listed and one for which it is not: upon detection of the non white-listed Femto, the UE would consider the LAC forbidden for 24 hours and would not reselect to the white listed Femto when detecting it.

To resolve this, LAC assignments should be coordinated with where the UEs are white listed.


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Standard and Proprietary Access Control

Currently deployed Femtos do not necessarily follow the standard, which leads to minor differences in the call flow. Such differences can be perceived in the way the LAU is rejected:

• From the standard (25.467), the LAU should be rejected by the HNB-GW, which would increase the signaling load between the Femto and the gateway.

• Proprietary implementations sometimes maintain a white list in the Femto, to allow access control to be done locally, without support from the gateway.

Some implementations may trigger UMTS Network Authentication Failure (e.g., based on “fake” AUTN) instead of LAC-based reject, although the mechanism would work only with USIM, and not with SIM.


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Rejection Cause

In addition to the typical rejection code #15, rejection code #13 (“Roaming not allowed”) can be used by the Femto. The standard 23.122 defines how the UE responds to each code:

• #13 – The UE initiates a PLMN selection

• # 15 – The UE attempts to find a cell in the same PLMN

Similarly, when an “authentication failure” is received (refer to 23.122, §4.4.4), the UE enters a “no SIM state” which causes the UE to stop any attempts to register on any PLMN. This failure cause value is not recommended to reject a UE from a Femto because this effectively disables the UE until a power cycle.


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PLMN for Femto

In this document, Femtos are assumed to be part of the same PLMN as the Macro network. In this case, no special provisioning is needed for the Femto user, which simplifies Femto deployment. As highlighted in Section 5, parameter settings that enable easy discovery of the Femto may impact the battery life of the UE.

Using a dedicated PLMN ID that only the Femto user would know as an equivalent PLMN would help save battery life for non-Femto users; battery life impact would be limited to only the UEs of Femtousers.


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Section 5: Parameter Settings for Legacy UEs and Networks

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Cell Reselection

The UE reselection process can be divided into two phases: Neighbor Cell Measurements and Neighbor Cell Ranking and Reselection. The main parameters and rules controlling these phases are summarized in the following slides.

RNC broadcasts reselection parameters for all UEs in its coverage area (can be set per cell).

The main cell reselection metrics/targets are:

• Camping cell quality (affecting out-of-service, MO/MT call setup/retainability)

• UE battery and/or other camping strategies/targets (e.g., prioritizing certain cells/carriers)

• For inter-LAC reselection, the ability to reach the user and Over the Air (OTA) signaling are also crucial metrics, because reselection will cause a NAS registration, during which time the UEcannot be paged.

Handover

The handover procedure can be divided into:

• UE performing /detecting the configured measurements/events

• UE reporting measurements and/or events to the RNC

• RNC commanding the handover to the UE

RNC can configure dedicated UE measurements/event reports (can be set differently for CS and PS).

Main handover metrics are: call quality/retainability, OTA signaling, unnecessary Compressed mode operation /duration (for inter-frequency/RAT measurements), other handover strategies/targets (e.g., offload certain cells/frequencies).


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Femto Cell Reselection Aspects

As described in the following slides, tuning cell reselection parameters in the presence of Femtos is highly dependent on several factors, including the Femto discovery strategy (whether a Femtoshould be considered the same or higher priority than Macro cells), the Femto Access Control strategy (whether Femtos are Open for all users or Closed to one or a few users), spectrum availability, and strategy (how many carriers are available and which carrier should be dedicated to Femtos or shared with Macro cells).

Some native constraints of legacy cell reselection are summarized below:

• Access Stratum (AS) layer cell reselection is based on measurement and ranking of neighbor cells that are identified mainly by their PSC (Primary Scrambling Code) in the broadcast Neighbor List (SIB11 NL). Therefore, there is no distinction between Macro and Femtos at the UE during cell reselection. Nevertheless, HCS can be used to prioritize measurement and reselection of specific PSCs, thus allowing selected Femto prioritization.

• The broadcast nature of the cell reselection parameters does not support:

– The Select-My-Femto approach, because parameters would apply to ALL users camping on a cell.

– Controlled Access control per UE, because access can be either allowed or barred to all users. NAS access control would be required to support Closed Access per user/UE, as described earlier (LAC-based registration).


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Femto Discovery and Reselection Strategies

Two main cell reselection parameters tuning strategies are considered in the following slides: Best Coverage (UE reselects the best cell regardless of type: Femto or Macro), and Femto Priority (prioritize search and reselection of Femtos). The Femto priority strategy might be used to offload Macro capacity or due to special tariff plans offered to Femto customers.

Both strategies may work with both Select-My-Femto and Select-Any-Femto approaches, although certain scenarios may be more suitable for one or the other. For example, using Femto priority due to special tariffs may be best achieved with a Select-My-Femto strategy. On the other hand, if the goal is to offload Macro capacity or have the UE select best coverage, Select-Any-Femto may be the best strategy. The Select-My-Femto or Select–Any-Femto strategy also could depend on the Femtoenvironment or the type of premises. For example, Select-My-Femto may be better suited for residential or private/enterprise Femtos while public Femto hot-spots (such as indoor train stations or shopping malls) may be better suited for a Select-Any-Femto approach.

One constraint of legacy cell reselection is that it is not suitable for the Select-My-Femto approach; this could cause issues for both Best Coverage and Femto Priority strategies.

One major difference between these two strategies is UE stand-by time impact. The Femto Priority strategy relies on aggressive reselection parameters that maximize Femto discovery and reselection efficiency at the cost of reduced stand-by time. The Best Coverage strategy can instead work with more relaxed parameters, thus having less impact on UE battery. This is explained in the following slides.


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Parameter Settings For Best Coverage vs. Femto Priority

The main parameters strategy for the Best Coverage approach is to let the UE camp on and reselect the best cell, without any specific biasing toward Macro or Femtos. Typical measurement triggers used in Macro cells and reselection hysteresis to avoid ping-ponging can be applied to Femtos as well. Because no specific priority is needed, HCS is not useful for the Best Coverage approach, and therefore not considered in this discussion.

In case of Femto Prioritization, cell reselection parameters should be tuned to find and reselect a Femto as soon as it would be available (and suitable, in terms of signal quality or strength), which implies both in good and bad Macro quality conditions. This impacts the UE stand-by time, so a compromise setting should be found.

In order to prioritize Femto reselection, parameters need different settings on Macro and Femtos. This could be achieved using both HCS and non-HCS rules, as shown in the next slides.

When a UE is camping on a Macro cell, it should look and reselect to Femtos as soon as possible, when in proximity of a Femto. This should also happen in good Macro RF coverage.

When a UE is camping on a Femto, it should stay there as long as the Femto maintains sufficient quality, thus neighbor cell measurements and reselections can be minimized/delayed (at least as long as Femto quality does not degrade significantly).

Some parameter examples for both strategies are shown in the following slides. For the FemtoPriority strategy, different carrier deployment scenarios are also considered.


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Open and Closed Access – Impact on Any Cell Reselection

The Open/Closed Access strategy generally depends on the Femto environment or premises type. For example, Closed Access may be better for residential or private/enterprise Femtos while public Femto hot-spots (such as indoor train stations or shopping malls) may be better suited to an Open Access model. The selected strategy may also depend on other factors such as capacity and QoSconstraints.

Open Access

Except for the Select-My-Femto approach (which may not be realistic for an Open Access approach), Open Access works quite well with legacy cell reselection. Parameters can be set similarly on Femtoand Macro SIBs, if coverage/quality is the main target (this is discussed later).

Closed Access

Legacy cell reselection rules do not natively support Closed Access per UE. In fact, Closed Access for legacy UEs can be inefficient. In particular:

• It shall be enforced at NAS level, by forcing LAC-based registration (thus UE-CN signaling)

• A UE can (re)select not-allowed Femto(s), generating unnecessary NAS registrations. UE registration rejection can cause an Out Of Service (OOS) condition, depending on the cause value, and may be more severe in shared Macro/Femto carriers.

A few differences may apply to cell reselection settings in closed Femto access. As shown later, Femtos may not include other Femtos in the reselection Neighbor List.


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Measurement and Reselection Rules

Major standard references for the cell reselection rules described in the next slides are 3GPP TS 25.304 and TS 25.331.


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Cell Reselection – Measurement Rules

The measurement rules shown above apply to Rel 99 onward if HCS is not used. In summary, intra-frequency, inter-frequency, and IRAT measurements are controlled by broadcast Sintrasearch, Sintersearch, and SsearchRAT thresholds.

RSCP-based thresholds can be set in addition to Ec/No thresholds (minimum suitability = Qrxlevmin):

• SsearchHCS , triggering inter-frequency measurements

• SHCS-RAT, triggering IRAT measurements

In particular, the “OR” rule is defined:

• If Sx <= Sintersearch, or Srxlev <= SsearchHCS if SsearchHCS is signalled, perform inter-frequency measurements.

• If Sx <= SsearchRAT m, or Srxlev <= SHCS,RATm if SHCS,RATm is signalled, perform measurements on cells of RAT “m”.

Although “HCS” naming is used, these thresholds can also be set/used, from Rel 5 onward, when HCS is not used.

Note: If Sintersearch is not sent for the serving cell, the UE shall perform inter-frequency measurements. If SsearchRAT m is not sent for serving cell, UE shall perform measurements on cells of RAT “m”.

All above parameters are broadcast in SI Type 3 (over the BCH channel). Measurements should be limited to a Neighbor List (NL) broadcast in SI Type 11 (together with other parameters, see next slides).


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Cell Reselection – Ranking/Reselection Rules

The above rules apply to Rel 99 onward if HCS is not used and in low mobility (this is discussed later).

The R criteria is used to rank neighbor cells and serving cell. For the serving cell, the UE uses:

• Qhyst1/2 – Hysteresis applied to the serving cell on CPICH RSCP/ Ec/No measurements.

For each neighbor cell, the UE is given the following parameters:

• Qoffset1/2 – Offset applied to the neighbor cell on CPICH RSCP/ Ec/No measurements.

Until point T0 Cell 1 is the highest ranked cell, so no reselection occurs.

• At point T0 Cell 2 becomes the highest ranked cell, but must remain the highest ranked for Treselection seconds. Cell 1 remains the serving cell.

• At point T1 Cell 2 has remained the highest ranked cell for Treselection seconds, and becomes the new serving cell.

While Qhyst is broadcast in SIB3, all other reselection parameters are broadcast in SIB11, with Qoffset

configurable per each neighbor cell. A different Qqualmin and Qrxlevmin can also be set per neighbor cell, which helps minimize certain ping-pong issues, as described later.

A few additions have been introduced since Rel 5 (see Appendix A). For example, different Qhyst / Treselection for RRC dormant states and different Treselection scaling factors for inter freq/RAT .


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Hierarchical Cell Structure (HCS) Overview

The Hierarchical Cell Structure (HCS) feature was inherited from GSM but has different usage in WCDMA. While the conventional usage of HCS for GSM umbrella cells is not as efficient in WCDMA (due to interference), HCS can be used in WCDMA to control the prioritization of specific cells/layers e.g., in multi-carrier scenarios or in the presence of Femto, Pico, or Micro cells.

HCS also offers other specific mechanisms that may be useful in WCDMA, such as controlling the cell reselection rate and using RSCP as triggering quantity for inter-frequency and/or inter-RAT measurements. These mechanisms can be used for pre-Rel 5 UEs only with HCS. For Rel 5 onward UEs, the same mechanisms have been defined for non-HCS reselection as well.

Low/High Mobility condition (for both HCS and non-HCS reselection) is based on the rate of cell reselections rather than actual mobility/speed. The specification defines high mobility as: if the number of cell re-selections exceeds a certain threshold Ncr (1 to 16) within the last Tcr (30 to 240) seconds (with Ncr and Tcr broadcast by the RNC). The low/high mobility criteria apply to Femtosearch in that low mobility UEs should search for Femtos, while high mobility UEs should not.

The reselection rate can be a false indication of actual UE mobility (e.g., high speed near-cell UEsmay perform very few reselections while low speed UEs at the border may perform many). This may alter the Femto prioritization strategy: high speed near-cell UEs would unnecessarily look for Femtos while low speed UEs at the cell border would not search for Femto. Due to these issues, mobility conditions are not considered in these slides. Therefore, only Low-Mobility rules apply for both HCS and non-HCS.


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Cell Reselection – HCS Measurement Rules (Low Mobility)

Standard HCS measurement rules are summarized below.

For intra-frequency and inter-frequency threshold-based measurement rules, use Squal for FDD cells:

• If (Srxlevs <= Ssearchhcs) or (if FDD Squal <= Sintersearch) THEN measure all intra-frequency and inter-frequency cells

• ELSE IF (Sx > Sintrasearch) THEN measure all intra-frequency and inter-frequency cells that have higher HCS priority level than the serving cell

• ELSE measure all intra-frequency and inter-frequency cells that have equal or higher HCSpriority level than the serving cell

If HCS is used and if Sintrasearch or SsearchHCS or Sintersearch (in FDD) are not sent for the serving cell, UEshall measure all intra-frequency and inter-frequency cells.

For Inter-RAT threshold-based measurement rules, use Squal for FDD cells:

• IF (Srxlevs <= Shcs,rat) or (if FDD Squal <= SSearchRATm) THEN UE shall measure all IRATm cells:

• ELSE IF (Sx > Slimit,SSearchRATm ) THEN UE need not measure neighboring cells in RAT "m"

• ELSE UE shall measure all neighboring cells in RAT "m“ that have equal or higher HCS priority level than the serving cell unless measurement rules for fast-moving UEs are triggered


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Cell Reselection – HCS Ranking/reselection Rules (Low Mobility)

The HCS minimum absolute criteria H can be compared to broadcasting a Qqualmin for the SIB11 neighbor cells when using non-HCS rules. Thus the specifics of HCS ranking are:

• Selective ranking based on HCS priority.

• Ability to define a temporary offset, either on the H (absolute threshold) criteria for different HCS priority cells, or on the R (relative ranking) criteria for same HCS priority cells.

Rules on Tn: The timer Tn is implemented for each neighboring cell. Tn shall be started from zero when one of the following conditions becomes true:

• If (HCS_PRIOn <> HCS_PRIOs and Qmeas,n >= Qhcsn) OR (HCS_PRIOn = HCS_PRIOs ) and

• For serving FDD and neighbor FDD cells if the quality measure for cell selection and reselection is set to CPICH RSCP in the serving cell, and Qmeas,n > Qmeas,s + Qoffset1

• For serving FDD and neighbor FDD cells if the quality measure for cell selection and reselection is set to CPICH Ec/No in the serving cell, and Qmeas,n > Qmeas,s + Qoffset2s,n

• For all other serving and neighbor cells: Qmeas,n > Qmeas,s + Qoffset1s,n

Tn for the associated neighbor cell shall be stopped as soon as any of the above conditions is no longer fulfilled. Any value calculated for TOn is valid only if the associated timer Tn is still running; otherwise, TOn shall be set to zero.


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Best Coverage – Parameters Strategy

The above example configuration matches an unbiased cell reselection strategy (no prioritization for specific WCDMA cells or frequencies). This configuration would enable trade-off between:

• The best camping cell quality, for which high measurement thresholds would be desired.

• The UE stand-by time, for which too many/frequent measurements would be detrimental.

This configuration may apply to different carrier scenarios (shared/dedicated Femto carriers).

Because prioritization is not important, HCS parameters are not needed.

As shown in the picture, the chosen configuration would cause a UE to trigger intra-frequency measurements earlier than inter-frequency. This is a typical approach for inter-frequency measurements, which have more impact on UE stand-by time, at least in a 1-1 overlay scenario. Hot spot 2nd-carrier settings may differ. For example, hot spot border cells may trigger inter-frequency measurements earlier.

Qhyst + Qoffset = 3 dB and Treselection = 1 sec are also typical settings, with a goal of minimizing ping-pong via ranking and temporal hysteresis, and allowing a specific level of user distribution among carriers.

Although the above diagram shows parameters based on Ec/No quality measure, the same approach can be used for RSCP parameters (applicable to Rel 5 onward UEs only with non-HCS).


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Prioritizing Femto with non-HCS Parameters

Two main parameter options apply for prioritizing Femto: non-HCS and HCS. The following slides summarize the non-HCS parameters strategy based on the carrier deployment scenarios shown above.

The examples in the next slides assume an aggressive Femto search strategy (always search for Femto). This may have a significant impact on UE stand-by time. Actual parameter settings could be less aggressive to achieve a compromise between fast Femto discovery and UE battery life.

A basic assumption on enabling Femto-Macro reselection is:

• Macro cells will add Femto PSCs to their SIB11 Neighbor List

• Femtos will add Macro PSCs to their SIB11 Neighbor List


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Prioritizing Femto – Macro Parameters Strategy – non-HCS – Shared Carrier

To force the UE to find Femtos quickly, Sintrasearch can be set very high. This triggers frequent intra-frequency measurements. The additional Macro searches and potential reselections (i.e., in the absence of suitable Femto signal) will provide an average better Macro serving cell quality at the cost of higher UE battery drain. As mentioned later, this will not occur with HCS.

Once a Femto has been measured, since ranking will include measured cells plus the serving cell, a large (negative) Qoffset for Femtos is proposed to make sure that a Femto is reselected regardless of the Macro cell quality (i.e., Rn = Femto quality – Qoffset = very high).

This may cause an issue in terms of Femto suitability, with high risks of ping-pong: a UE can reselect to a Femto given the “biased” ranking offset, then realize that the Femto quality is not suitable. To minimize such issues, it is recommended to set Qqualmin,n (Femto) in Macro SIB11, which represents a minimum quality criteria for the UE to reselect to a Femto, regardless of its ranking, and provides a certain cell reselection hysteresis. The concept is illustrated in the next slide.

Other cell reselection parameters: Qoffset,n (Macro) = 0; Treselection = 1 sec. Those values provide a minimum reselection hysteresis (Qhyst = 3 dB) and a fast reselection.

Though the above diagram shows the parameters configuration based on Ec/No quality measure, the same approach can be followed using RSCP-based thresholds and parameters (applicable to Rel5 onward UEs only with non-HCS parameters).


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Prioritizing Femto – Femto Parameters Strategy – non-HCS – Shared Carrier

On the Femto side, in order to keep the UE camped on the Femto as much as possible, a low Sintrasearch

threshold should be configured so the UE will not perform measurements. In this case, the UE would not reselect to Macro as long as the Femto quality is above the configured threshold. Due to the limited Femto coverage, out-bound reselection shall be configured safely to avoid OOS cases when leaving the Femto area.

This diagram illustrates cell reselection hysteresis provided by the Macro broadcast Qqualmin for Femto neighbors. A UE will reselect to the Femto if its Ec/No quality is above -10 dB, providing cell suitability plus avoiding/minimizing Macro-Femto-Macro ping-pongs.

Other cell reselection parameters:

• Qoffset,n (Macro) = 2, to provide a certain biasing toward Femto quality for ranking: effectively the Macro cell quality should be Qhyst + Qoffset = 5 dB better than the Femto to trigger reselection.

– If reselection to other neighboring Femtos is desired, Sintrasearch could be increased together with the Macro Qoffset, so that ranking prioritization would take care of Femtopriority.

• Treselection could also be set > 1 sec (e.g., 2 to 3 seconds), to enure that reselection to Macro happens only when the Macro quality is significantly better (than Femto) for a certain time.

Although the above diagram shows parameters based on Ec/No quality measure, the same approach can be used for RSCP parameters (applicable to Rel5 onward UEs only with non-HCS).


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Prioritizing Femto – Macro Parameters Strategy – non-HCS – Dedicated Carrier

To help/force the UE to find Femtos (on the other carrier), Sintersearch can be set very high.

Because ranking will include measured cells plus the serving cell, once a Femto has been measured, a large (negative) Qoffset for Femtos is proposed to ensure a Femto is reselected regardless of the Macro cell quality (i.e., Rn = Femto quality – Qoffset = very high).

This may cause Femto suitability issues, with a high risk of ping-pong: a UE can reselect to a Femtodue to the “biased” ranking offset, then realize that the Femto quality is not suitable. To minimize such issues, it is recommended to set Qqualmin,n (Femto) in Macro SIB11, which represents a minimum quality criteria for the UE to reselect to a Femto, regardless of its ranking, and provides a certain cell reselection hysteresis. (This concept was illustrated in the previous slide.)

Other cell reselection parameters: Qoffset,n (Macro) = 0; Treselection = 1 sec. These values provide a minimum reselection hysteresis (Qhyst = 3 dB) and fast reselection.

From Rel 5 onward, a specific Treselection for inter-frequency reselection can be defined as a scaling factor for the intra-frequency Treselection, if there is need to differentiate among them.

The above settings can be used for RSCP parameters (for Rel 5 onward UEs).

If the UTRAN implementation does not allow setting Sintrasearch < Sintersearch, these parameters may be set to the same value, causing more intra-frequency searches and potential reselections, which will improve cell quality but will drain more UE battery.


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Prioritizing Femto – Femto Parameters Strategy – non-HCS – Dedicated Carrier

On the Femto side, parameter configuration considerations are similar to the shared carrier scenario.

One significant difference in the dedicated carrier case is triggering of Femto and Macro measurements can be differentiated by means of Sintrasearch and Sintersearch. If neighboring Femtoreselection is desired, Sintrasearch could be set higher than Sintersearch to prioritize Femtomeasurements/reselection.



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Prioritizing Femto – Macro Parameters Strategy – non-HCS – Multi-Carrier

To force the UE to find Femtos quickly, Sintrasearch and Sinterserach can be set very high. This triggers the frequent intra- and inter-frequency measurements necessary to detect Femto on the same carrier and other neighbor carriers.

Other considerations are similar to the previous scenarios.

The configuration shown above assumes there is no specific differentiation/biasing strategy between F2 and F3 Macro cells.

(**) To avoid forced frequency biasing, Sintrasearch on F1 would need to be set equal to Sintersearch, otherwise UEs may reselect to F2 or F3 Macro cells in the absence of a Femto signal but in good F2 or F3 coverage. This may imply some additional intra-frequency measurements and potentially higher Macro cell reselection rate.

The additional Macro searches and potential reselections (in the absence of a suitable Femto signal) caused by Sintrasearch and Sintersearch settings applicable to F1, F2, and F3 will provide, on average, better serving cell quality at the cost of reduced UE battery life.

This issue will not occur with HCS (as discussed later).



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Prioritizing Femto – Femto Parameters Strategy – non-HCS – Multi-Carrier

On the Femto side, many considerations described for the previous scenarios are applicable for the multi-carrier case, i.e., combining shared and dedicated carrier constraints and targets.

As a result of those combined targets, Sintrasearch and Sintersearch both can be set low to delay measurements of Macro cells in the same or a different carrier. If reselection to neighboring Femtosis desired, the thresholds can be increased and Qoffset (Macro) can be set to guarantee Femtoprioritization during ranking.

Although the above diagram shows parameters based on Ec/No quality measure, the same approach can be used for RSCP parameters (applicable to Rel5 onward UEs only with non-HCS).


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Prioritizing Femto with HCS parameters

Two main parameter options apply for prioritizing Femto: non-HCS and HCS. The following slides summarize the HCS parameters strategy based on the carrier deployment scenarios shown above.

Assuming low mobility conditions (due to the high-mobility issues explained in the HCS introductory slides), HCS prioritization would achieve the Femto priority strategy by simply assigning higher HCS priority to Femtos so they are always searched and measured, and ranked/reselected, if suitable. As for non-HCS prioritization, this will impact UE stand-by time.

Unlike non-HCS, the always-search for higher priority cells cannot be avoided or tuned with HCS, if low mobility conditions are used.

Same as non-HSC, a basic assumption for enabling Femto-Macro reselection, is:

• Macro cells will add Femto PSCs into their SIB11 Neighbor List

• Femtos will add Macro PSCs into their SIB11 Neighbor List

The following slides present some example parameter configurations suitable for prioritizing Femtowith HCS, and in different spectrum/carrier allocation scenarios.


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Prioritizing Femto – Macro Parameters Strategy – HCS – Shared Carrier

Unlike non-HCS parameters, HCS measurement thresholds control measurement toward higher priority, same priority, or lower priority cells based on the configured HCS priority (0 for Macro, 1 for Femto in the above example).

For the specific shared carrier scenario, Macro parameters should be set to ensure that:

• UE will always measure/rank and reselect to Femtos as long as they are available and suitable (based on the H criteria; i.e., quality is higher than Qhcs). When a specific Femto is detected (and fulfills the H criteria) the serving Macro cell will not be ranked since it is not part of the highest priority cells, so there is no need to bias resection with specific Qoffset.

– The Qhcs threshold can be considered similar to the Macro broadcasting of Qqualmin for those Femto PSCs added in the SIB11 Neighbor List, which mainly controls Femtosuitability and minimizes Macro-Femto-Macro reselection ping-pongs.

• Sintrasearch will control the triggering of intra-frequency Macro measurements for the Macro-to-Macro reselection, which can be set to the typical value used without Femto priority requirements.

Specific HCS measurement thresholds and other cell reselection parameters suitable for this scenario are summarized at the end of this section, in the parameters exercise/example section.


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Prioritizing Femto – Femto Parameters Strategy – HCS – Shared Carrier

Unlike non-HCS parameters, HCS measurement thresholds control measurement toward higher priority, same priority, or lower priority cells, based on the configured HCS priotiy (0 for Macro, 1 for Femto in the above example)

For the specific shared carrier scenario, Femto parameters should be such to ensure that:

• UE will not measure other cells above Sintrasearch (no cells with higher priority than current serving Femto).

• Sintrasearch will control the triggering of intra-frequency Femto measurements, if needed (open access or restricted access among neighbor Femtos belonging to the same restricted group).

• Sintersearch will control the triggering of intra-frequency Macro measurements, which should start late based on the Femto prioritization strategy.



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Prioritizing Femto – Macro Parameters Strategy – HCS – Dedicated Carrier

Similar to the shared carrier scenario:

• UE will always measure/rank and reselect to Femtos as long as they are available and suitable.

• Sintrasearch will control the triggering of intra-frequency Macro measurements for the Macro-to-Macro reselection, which can be set to the typical value used without Femto priority requirements.

One major difference for this scenario is that UE stand-by time impact due to continuous inter-frequency measurements will be even worse than intra-frequency measurements.



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Prioritizing Femto – Femto Parameters Strategy – HCS – Dedicated Carrier

Similar to the shared carrier scenario:

• UE will not measure other cells above Sintrasearch (no cells with higher priority than current serving Femto).

• Sintrasearch will control the triggering of intra-frequency Femto measurements, if needed (open access or restricted access among neighbor Femtos belonging to the same restricted group).

Sintersearch , in this scenario, will control the triggering of inter-frequency Macro measurements, which should start late based on the Femto prioritization strategy.



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Prioritizing Femto – Macro Parameters Strategy – HCS – Multi-Carrier

In a mulit-carrier scenario, the measurement threshold settings will be similar to the other scenarios. The major difference is in the type of cells/frequencies the UE shall always measure. In particular Sintrasearch will trigger:

• On F1, inter-frequency measurements to search for Femtos (high priority) on F2 and F3.

This differs from non-HCS, for which Sintrasearch and Sintersearch need to be equal and need to be set high on F1 in order to not favor F2 and F3 Macro cells in the absence of Femtos, thus requiring some extra intra-frequency measurements.

• On F2 and F3, intra- and inter-frequency measurements to search for Femtos (high priority) on F1, F2, and F3.

The above configuration (same Sintrasearch for F1, F2, and F3) assumes no special prioritization or differentiation among Macro carriers.



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Prioritizing Femto – Femto Parameters Strategy – HCS – Multi-Carrier

While the threshold settings are similar to previous scenarios, the UE will simply perform more measurements given the distribution of Femtos across multiple carriers. In particular:

• Above Sintrasearch the UE will not perform any neighbor measurements

• Below Sintrasearch the UE will meausre other Femtos (intra- and inter-frequency), if needed/desired

• Below Sintersearch the UE will measure also Macro cells (intra- and inter-frequency)



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HCS vs non-HCS for Femto Priority

As summarized above, both HCS and non-HCS reselection settings can achieve Femto prioritization at a similar cost in terms of UE stand-by time, at least in terms of Femto search and reselection impacts. The main differentiating factors between the 2 types of settings are:

• HCS

– Targeted Femto search via HSC priority. Without HCS, the only differentiation is between intra-frequency, inter-frequency, and IRAT cells. This may cause additional Macro searches and/or reselections, especially in the absence of Femto signal/coverage, thus better average cell quality is achieved at the expense of reduced UE battery life.

– Flexible priorities are useful, for example, to offset traffic between carriers while minimizing UE battery drain (e.g., to specify that a certain Macro carrier should be measured at a different quality threshold than others). Without HCS, measurement triggers cannot be differentiated among multiple carriers — only ranking/reselection parameters (e.g., Qoffset) can be set per carrier.

• Non-HCS

– Fewer parameters to configure, manage, and optimize. (HCS would imply more parameters and headaches for the optimization folks.)

– It is fully supported by all UEs and networks. (Some (old) UEs and networks have been reported to not fully support HCS.)


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Parameters - Quiz

Enter suitable parameter values or ranges where indicated in the table.


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HCS vs. Non HCS – Pros/Cons

No major difference expected in terms of reselection quality and stand-by time.

Camping on Macro

• HCS: UE will always search for Femtos only. As soon as a good Femto is found, UE will reselect to it. It is possible to set a different serving cell quality threshold for starting Macro cells measurements.

• Non-HCS: UE will always search for both Femto and Macro cells. As soon as a good Femto is found, UE will reselect to it, due to Qoffset setting. The additional Macro searches and potential reselections (in the absence of suitable Femto signal) caused by high Sintrasearch will provide a better average Macro serving cell quality at the cost of reduced UE battery life. This issue will not occur with HCS.

Camping on Femto

• HCS: UE can start measuring Femto and Macro cells at different serving cell quality thresholds.

• Non-HCS: UE will start measuring Femto and Macro cells at the same serving cell quality threshold. Differentiation is achieved by different Qoffset settings.

Note: The parameter values discussed here apply only to this example. Configured values used in the field should be tuned according to real /specific scenarios, conditions, and constraints, preferably after testing and/or KPI monitoring/assessment.


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Parameters - Quiz



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HCS vs. Non HCS – Pros/Cons?

Similar considerations apply for shared Femto/Macro carriers.

For inter-frequency measurements, if different prioritization is needed among Macro layers (e.g., in a multi-band scenario or when a certain camping carrier should be preferred), additional pros and cons apply:

• HCS can set different priorities, thus UE can selectively measure and reselect specific carriers.

• Non-HCS will require the UE to measure all inter-frequency cells at the same time, while reselection shall be controlled by different Qoffsets, thus stand-by time impact can be larger.

The above non-HCS constraint will cause additional Macro searches and potential reselections (i.e., in the absence of suitable Femto signal) , which will provide a better average Macro serving cell quality at the cost of higher UE battery drain. This is an issue that will not occur with HCS.



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Parameters - Quiz



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HCS vs. Non HCS – Pros/Cons

If there are only 2 carriers, one for Femto and one for Macro, HCS and non-HCS settings will produce very similar effects.

Sintrasearch and Sintersearch can be used in Macro and Femtos to differentiate/prioritize Femto and Macro

cells.

The only drawback with non-HCS settings will be that, for Macro-to-Femto, the Macro serving cell will always be ranked, thus negative Qoffset shall be set for Femto neighbors in order to prioritize reselection to them. To reduce ping-pong effects, a minimum threshold for Femto reselection shall be configured (e.g., -12 dB Ec/No)

If multiple dedicated carriers are deployed, differentiation among inter-frequency cells will not be possible with non-HCS, as described in the previous scenario.



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Femto Handover Procedures

WCDMA defines both soft handover (for intra-frequency handover only) and hard handover (for intra-frequency, inter-frequency, and IRAT) for Macro Connected mode (cell_DCH) mobility.

In the presence of Femtos without Iur connection with Macro (and between Femtos), Macro-diversity and soft handover are not possible; the only suitable procedure is hard handover.

Hard handover will be inter-RNC and intra-frequency or inter-frequency depending on the Femto-Macro carrier deployment scenario.

The procedure itself involves moving both signaling and User Plane from the source RNC to the target RNC at once, including the relocation of the Iu connection to/from the CN. Given the abrupt transition/relocation of bearers from one RNC to the other, hard handover is generally more risky than soft handover, which always maintains an active connection toward one of the ASET cells while adding/removing other radio links.

The handover can be intra-CN node (MSC/SGSN) or inter-CN node depending on the Femto network configuration (i.e., whether there will be a dedicated/separate MSC/SGSN handling the Femtos than the one serving the surrounding Macro cell, or based on how many MSC/SGSNs are used to connect those Femtos spread inside one Macro cell).

The following slides summarize the signaling flows associated with inter-RNC hard handover, and the main challenges of Femto hand-in and hand-out.


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Intra-MSC/SGSN Backward Hard Handover

The above diagram illustrates the signaling flow for intra-MSC/SGSN hard handover.

The procedure is also called “Backward HHO”, according to 3GPP TR 25.931.

The flow can be split into three main phases:

• Handover triggering and preparation

• Handover execution, and

• Resource release in the source RNC

More details can be found in 3GPP TS 25.331 (RRC) and 25.413 (RANAP).

The flow for PS RABs (i.e., the intra-SGSN hard handover case), would be applicable only for cell_DCH RRC state. In other RRC Connected states (cell_FACH, Cell/URA_PCH) a different procedure applies, as described in the next slide.

For PS or CS, additional signaling would be required for inter-MSC or inter-SGSN handover (this signaling is not presented in the diagram, for simplicity). This additional signaling can be considered an extension of the above case, and would include:

• For CS, some MAP and ISUP signaling among MSCs while signaling to/from UE and to/from source/target RNC are the same. More details can be found in 3GPP TS 29.002.

• For PS, some GTP signaling among SGSNs and with GGSN to exchange UE contexts and update the GTP bearers/tunnels. Details can be found in 3GPP TS 23.060 and 29.060.


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Intra-SGSN Forward Hard Handover

The above diagram illustrates the signaling flow for intra-SGSN forward hard handover.

In any RRC Connected state other than cell_DCH (i.e., Cell_FACH, Cell_PCH, URA_PCH), the UE will perform Cell Update (Cell_FACH or Cell_PCH states) or URA Update (URA_PCH state) toward the target RNC. More details can be found in 3GPP TS 25.331 (RRC).

When receiving these messages, the target RNC will send an RRC Connection Release message with cause “Directed Signaling Connection re-establishment" when it is unable to contact the SRNC to validate the UE due to lack of Iur connection.

This will trigger the UE to perform a Routing Area Update and subsequently a Service Request to re-establish the RABs.

After this, the SGSN will ask the target RNC to set up the corresponding RABs, which will trigger an RB set-up procedure over the air.

After setting the RAB(s) on the target RNC, the SGSN will release resources on the source RNC.

The inter-SGSN handover procedure (not shown here, for simplicity) is an extension of the above description - new and old SGSNs will exchange UE information (GMM contexts and PDP contexts) during the Routing Area Procedure. See 3GPP TS 23.060 for details on the inter-SGSN Routing Area Update.


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Femto Hand-in

Femto hand-in has a major issue with legacy handover procedures, caused by the re-use of PSC for Femtos. This issue may be severe for shared carrier scenarios and also dedicated carriers with dense Femto deployments.

Due to the PSC re-use, once a UE arrives in the proximity of a Femto and reports its PSC and the measured quality to the Macro RNC, if configured to do so, the RNC will not be able to identify which Femto the UE is approaching, among all the Femtos inside the Macro cell coverage area that share the same PSC. As described later, this issue has been resolved in the Rel 9 standards by adding information to the UE report that enables the RNC to uniquely identify the reported target cells.

PSC-confusion may or may not be an issue for Femto-to-Femto handover; that is, it would not be a problem for enterprise deployments with properly configured Neighbor Lists for each Femto, if those few neighboring Femtos do not re-use the same PSCs.

Another issue related to legacy hand-in, which has also been addressed in Rel 9 standards, is the possibility to perform access control, for unauthorized UEs, at the source RNC, i.e., performing handover to a target Femto cell only if the UE is allowed to access it. In the absence of such access control at the source, the handover request may need to go through the Core Network in order to trigger proper IMSI-based access control, thus costing some extra Iu signaling load and false HO preparation requests.

Due to the above issues, and the general lack of support for hand-in in today’s Femto products, Femto hand-in is not discussed in detail in this course.


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Femto Hand-in

This slide shows how, despite hand-in issues due to PSC-confusion, hand-in may work in some scenarios, such as:

• Low density Femto penetration in dedicated Femto carrier scenarios, allowing allocation of up to 512 PSCs to Femtos. In this case, the limitation would be due to the Neighbor List size, because only 32 neighbors can be configured per carrier. If multiple carriers are allocated to Femtos, the number of confusion-free PSCs would actually increase.

• Proprietary RNC or Femto gateway solutions allowing an attempted Femto hand-in by trying a few or all the Femtos re-using a certain PSC.

Due to the lack of standard support for the above procedures, they are not discussed further in this course. The next slides discuss the challenges and parameters settings for the hand-out procedure.


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Femto Hand-out Events

Handover from Femto may be configured based on different triggers and strategies. Given the limited coverage provided by a Femto, one needed trigger would be coverage/quality degradation. Unlike hand-in, it is unlikely that hand-out will have PSC-confusion because the Macro PSC should be confusion-free for the Femto (either one or a few Macro cells will be measurable at the Femtopremises). If hand-in is not supported, this removes the risk of HO ping-pongs, so the main concern would be call retainability.

Different types of HO triggers (or a combination of them) are used for Macro handover, and could be used for Femto hand-out as well. Below is a short glossary of the terminology used:

• QBHO: triggered by UE measurements on the source/target cell, also called MAHO or non-blind.

• LBHO: triggered by network load conditions (e.g., source cell power or other resource load).

• DAHO: target cell information stored in a local database, also called blind HO (no UEmeasurements on the target cell); it may use UE measurements on the source cell or be triggered by load conditions.

• Intra-/Inter-frequency HO: intra WCDMA handover; intra or inter-frequency depending on the target carrier.

• IRAT HO: handover to GSM; specifications also define Service Based Handover (SBHO) for IRAT; i.e., the CN can indicate to the RNC (Femto) whether a certain RAB “shall, should, should not” be handed over to GSM.

Femto-to-Femto HO may work as Femto-to-Macro HO assuming there is no PSC-confusion among the neighboring Femtos.


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Femto Hand-out Events

Handover can be triggered based on periodic reports or specific events. The focus here is on event based handover, which is typically used. All handover events are based on AS size =1 (assuming no SHO for Femtos). Multiple events or combinations of events can be used to trigger Femto hand-out; the above table lists only some of the events that are typically used for Macro handover.

The next slides focus on absolute quality criteria events (1f, 2d, 2b, 3a), showing some typical signaling and a few parameter examples.

Details on event triggering criteria and parameters can be found in 3GPP TS 25.331 section 14.2.

Typical parameters associated with most of the above events, crucial for optimization, are:

• Time-To-Trigger: Period of time the event triggering condition must be satisfied before transmission of the Measurement Report message can occur.

• Hysteresis: Hysteresis between the condition to activate and deactivate event reporting.

• Filter Coefficient: Equivalent time constant of the low pass filter applied to the quality measurement.

For relative quality events (e1a, e1c, e1d), an offset (CIO) can also be configured per cell. E1a uses a reporting range (relative to the ASET cell quality) to set the reporting threshold.

Some events can also apply a Weighting factor (W) on the measurements of ASET cells.


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Intra-frequency Handover Measurements and Reporting - Example

Assumption: Using periodic intra-frequency measurements on neighbor cells plus Event 1f for the serving cell quality (falling below a certain threshold).

Step 1: The UTRAN uses Measurement Control messages to configure e1f and intra-frequency measurements at the UE.

Steps 2 and 3: The UE sends Measurement Report messages to the UTRAN to report neighbor cell measurements and Event 1f (when detected).

Step 4: The UTRAN sends a Physical Channel Reconfiguration message to handover the UE to the target cell. The UTRAN can also use other messages such as Radio Bearer Reconfiguration and Transport Channel Reconfiguration.

Step 5: When successfully connected to the UTRAN on the target cell, the UE sends the Handover Complete message.

Handover delay from UE e1f and intra-frequency report until completion of Physical Channel Reconfiguration is expected to be shorter than inter-frequency/inter-RAT (see next slides).

Event TTT should be added to the HO delay to measure the time duration between the detected event (quality threshold satisfied) and the handover command.


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Inter-frequency Measurements and Reporting - Example

Assumption: Using e2d to activate Compressed Mode and e2b to trigger HO.

Step 1: The UTRAN uses Measurement Control messages to configure e2d and e2f measurements at the UE.

Step 2: The UE sends the Measurement Report message to the UTRAN to report e2d (the serving frequency quality is below an absolute threshold).

Step 3: The UTRAN uses Measurement Control messages to configure e2b measurements and corresponding Compressed Mode pattern. The UTRAN can also use Measurement Control messages to activate Compressed Mode and configure soft handover behavior on the target frequency.

Step 4: The UE sends the Measurement Report message to the UTRAN to report e2b (the serving frequency quality is below an absolute threshold and the target frequency is above an absolute threshold).

Step 5: The UTRAN sends a Physical Channel Reconfiguration message to handover the UE to the target frequency. The UTRAN can also use other messages such as Radio Bearer Reconfiguration and Transport Channel Reconfiguration to direct the UE to the target frequency.

Step 6: Upon successful connection to the UTRAN on the target frequency, the UE sends a Handover Complete message.


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Inter-RAT Measurements and Reporting - Example

Assumption: Using e2d to activate Compressed Mode and e3a to trigger HO.

Step 1: The UTRAN uses Measurement Control messages to configure e2d and e2f measurements at the UE. There can be multiple Measurement Control Messages if UTRAN is using Ec/No and RSCPbased measurements.

Step 2: The UE sends the Measurement Report message to the UTRAN to report e2d (the serving frequency quality is below an absolute threshold).

Step 3: The UTRAN can send a Physical Channel Reconfiguration to configure the Compressed Mode patterns.

Step 4: The UTRAN activates CM and configures Event 3a along with GSM neighbors in the Measurement Control message. The UE can then start measurements on the GSM neighbor inside the CM gap.

Step 5: The UE sends the Measurement Report message to the UTRAN to report e3a (the estimated quality of the currently used UTRAN frequency is below a certain threshold and the estimated quality of the other system is above a certain threshold).

Step 6: the UTRAN sends a Handover From UTRAN message to handover the UE to IRAT. Upon successful completion of the IRAT handover procedure, the UE sends a Handover Complete message. For the PS domain, the IRAT handover message is Cell Change Order.


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Hand-out Parameters – Quiz

Most HHO events with absolute thresholds (1f, 2d, 2b, 3a) have reporting hysteresis mechanisms: Effective threshold = Event threshold ± Hyst/2. For example:

• For e1f/e2d or e2b/e3a Used frequency, Effective threshold = Event threshold - Hyst/2

• For e1e/e2f or e2b/e3a Unused frequency, Effective threshold = Event threshold + Hyst/2

For simplicity, e1e/e2f thresholds (deactivating intra-frequency HO or Compressed Mode) are not shown here. Generally their thresholds are set 2 to 3 dB higher than the activating events (e1f/e2d).

A small hysteresis (2 to 3 dB) is typically suggested to reduce unnecessary/multiple event reports.

For HO quality measurements, each event can be set with one quality measure only, thus the assumption of using both Ec/No and RSCP is based on the capability/configuration to send two event instances (used by some vendors for inter-frequency and IRAT, for example).

Inter-frequency and IRAT HO could be configured together or individually, depending on handover strategy and vendor support of certain configurations/features. If both inter-frequency and IRAT HO are configured, Compressed Mode patterns (defined differently for inter-frequency and IRATmeasurements) can be activated together (based on the same event 2d threshold) or by using different activation thresholds.

Typically (and by standard requirement) inter-frequency measurements are shorter than IRAT.


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Hand-out parameters – Example


The reason for setting e2d below e2b/e3a used frequency is to shorten unnecessary Compressed Mode operation (which could cause higher UL interference with neighboring cells due to the higher power used in CM). It basically enables the HO event (e2b/3a) to be triggered as soon as the target frequency/RAT quality is sufficiently good. In this case, e2b/e3a used frequency triggering thresholds can be set the same as the e2f (deactivating Compressed Mode).

Another approach would be to start Compressed Mode few dB earlier than the HO thresholds (used frequency/RAT).

Although not shown (for simplicity), a Filter coefficient (e.g., 2 to 3) is suggested to minimize unnecessary event reporting due to signal quality fluctuations.


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Section 6: Femto Optimization Mechanisms

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Femto Optimization Mechanisms

The above mechanisms or features are non-standard enhancements or optimizations that could be implemented inside the Femto to help improve Femto performance and robustness while mitigating certain embedded issues such as interference.

Standard enhancements for Femto, starting from 3GPP Rel 8, are described in the next section.

Because current or future Femto products may support some of those features, or similar ones, the following slides describe their advantages.

As mentioned earlier, interference management techniques are always beneficial, and are particularly critical when:

• Femtos are deployed in areas of good Macro coverage: Ensure that Femto coverage is maintained over the entire target area. Femto Range Tuning and Home UE protection would provide the best results.

• Closed Access Femtos are deployed in areas of Limited Macro coverage: Guest UE protection and Femto Range Tuning would provide the best results.

• High Density Femto: All interference management techniques would be beneficial.

Qualcomm has tested and verified all the above features in the lab and/or in the field, due to planned support for them in the Qualcomm Femto chipset. Qualcomm has observed performance improvements with all of them. More details can be made available, if needed.


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Tx Power Calibration based on Network Listen

Tx power is set by measuring received signal levels from surrounding Macro and Femtos using Femto NLM (Network Listen measurements). For example:

• Transmit at high power if Macro condition is good

• Transmit at low power if Macro condition is poor

NLM-based power calibration works as a baseline method, but has some limitations:

• Mismatch in RF conditions measured by Femto NLM and those experienced by HUEs and MUEs (e.g., Femto near a window or in the basement)

• Desired coverage range is unknown and depends on home size


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Tx Power Calibration based on Mobile Assisted Information

Periodically fine tune power by using registration attempts and home user reports jointly.

• Transmit “not too hot, not too cold”

• Needed to address limitations of NLM-based algorithm (RF mismatch, etc.)

Registration attempts based power calibration:

• Users that are passing by or driving by register with Femto if the Femto and/or beacon leaks outside

• Number of registration attempts over a certain duration (e.g., 1 day) can be used to detect Femto and/or beacon leakage and adjust the range

Active home user assisted power calibration:

• Request an active home UE to periodically report Femto CPICH Ec/Io, Macro CPICH Ec/Io and PL on the Femto channel

• Request an active home UE to periodically report Macro CPICH Ec/Io and PL on the beacon channel


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Guest Mobile Protection

Power throttling: Reduce or completely shut down Tx power of beacon and/or Femto for some duration to protect Macro mobiles in the vicinity (e.g., guest UEs).

Detect guest or passing-by Macro UEs by continuously monitoring UL RSSI on Macro and/or Femtofrequencies using “mobile sensing” receive chain.

• UL RSSI above a certain threshold indicates Macro user in the vicinity.

Continue normal operation after a time out or when UL RSSI falls below a certain threshold.

• Detect nearby active Macro mobiles by monitoring RL RSSI on Macro frequencies.

• Temporarily reduce or shut down beacon Real-time protection.


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Home Mobile Protection

Large UL interference at Femto due to nearby uncontrolled UEs (such as Macro UE close to Femto) results in low throughput and error bursts for Home UE on the Uplink.

A solution to this problem is to apply attenuation in the presence of Uplink interference:

• When large UL interference is detected at Femto:

– Rapidly introduce attenuation Make interference comparable to noise floor

• When interference disappears:

– Slowly decrease attenuation Ready for next interference burst


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Femto Discovery Issues

For efficient offloading of capacity, it is desirable for Idle mode UEs to find and camp on their own Femto.

In good Macro coverage, however, the cell reselection procedure may not be triggered and the UEmay not discover its own Femto, especially in Femto or Macro dedicated carriers. In shared carrier scenarios, interference generated by the Femto (due to control or data channels) may more likely cause degradation of the Macro signal quality, thus triggering Femto discovery.

Increasing the Macro Sintersearch threshold in dedicated Macro carriers can improve Femto discovery but impacts the battery life of all UEs in the network because all UEs are forced to search, even under good Macro conditions.

One solution, described in the next slide, is to use Beacons to trigger search only when the UE is in the vicinity of a Femto.


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Femto Discovery via Beacons

Femtos transmit an intermittent and calibrated pattern of short beacon bursts on Macro frequencies.

• Short beacon bursts cause inter-frequency search and reselection for idle UEs.

• Beacons should be short enough to avoid voice quality degradation of any Macro UE within beacon coverage.

Layered beacon is designed to balance interference and coverage.

• Use low power beacon burst pattern most of the time → Minimizes interference.

• Higher power beacon burst pattern → Ensures good beacon coverage.

Throttling Tx power of the beacon in real-time helps protect active Macro UEs in the vicinity of the Femto (e.g., guest UEs).


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Mobile Sensing for Hand-in Optimization

Active hand-in feature enhances user experience with Femtos:

• Provides uninterrupted service by transferring voice calls from Macro to Femto

• Provides capacity off-loading benefit to operators

There is no standardized solution in 3GPP for active hand-in support for legacy UEs (until Rel 9, as discussed later); it is left to implementation and proprietary solutions.

Uplink mobile sensing is one solution that can help active hand-in.

• Mobile sensing can resolve Femto PSC confusion

• Requires Femtos to measure the UL Pilot energy of a mobile (detected using the allocated PSC) when directed by the network and report this energy to the network

• Network determines the target Femto by comparing reports from various Femtos


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Femto Tx Diversity

Tx diversity provides reliable voice quality and range extension (also true for Macro operation):

• Prevents deep fades

• Reduces significantly number of hard handovers

Thus, Femto Tx diversity would be beneficial to improve performance inside the Femto coverage.

Different standard/proprietary techniques can be used for Tx-Div, though CLTD would be amongthe best choices, as it is supported by the standard and it is a closed-loop method.


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UL Throughput Optimizations

UL Rx diversity is beneficial in slow fading conditions, and optimized Noise Rise (RoT) control helps improve Uplink performance in multi-user scenarios. This is also true for Macro cells.

UE enhanced receivers will also improve performance, both in Femto and Macro coverage areas.


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Standards

Standard enhancements described in the following slides refer to Dec-09 version of 3GPP specifications.


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3GPP standards – Rel 8 and Beyond Femto Features

3GPP started standardizing Femto functionalities in Rel 8.

This slide summarizes the main categories of features introduced in Rel 8, Rel 9, and Rel 10.

The following slides provide details on the main Rel 8 and Rel 9 features. These releases can be considered frozen (no new functionality is expected to be added, only correction CRs). Rel 10 is still open and under discussion, so no further details are provided in this material.

Standard enhancements described in the following slides refer to the Dec-09 version of 3GPP specifications.


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Standard Femto definitions

More details can be found in 3GPP TS 22.011 (Rel 8 onward) and 22.220 (Rel 9 onward).

Standard Service (Stage1) requirements for Rel 8 Femtos (from 22.011) are summarized in Appendix B, including requirements on Femto installation, identification and UE display, Femtomobility, and manual selection.

Rel 9 Service Requirements can be found in 3GPP TS 22.220, mainly introducing new concepts and requirements related to hybrid mode, temporary subscriptions and enhanced manual CSG selection.


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Rel 8 Standard Femto Architecture – Main Entities and Functions

HNB

• Equipment located on the customer’s premises that offers the Uu interface to the UE.

• Provides RAN connectivity using the Iuh interface and supports most RNC like functions.

• Supports HNB registration and UE registration over Iuh.

HNB-GW

• Terminates Iuh from HNB. Appears as an RNC to the existing Core Network over Iu interface.

• Supports HNB registration and UE registration over Iuh.

SeGW

• Terminates secure tunnelling for TR-069 as well as Iuh and provides authentication of HNB.

• Provides the HNB with access to the HMS and HNB-GW.

• May be implemented either as a separate physical element or integrated (e.g., into a HNB-GW).

HMS

• Provisions configuration data to the HNB.

• Performs location verification of HNB and assigns appropriate serving elements (HMS, Security Gateway, and HNB-GW).


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Rel 8 Iuh Protocol Stack

This slide shows the Control Plane and User Plane protocol structures over the Iuh interface.

Two new protocols have been introduced on the Control Plane:

• The HNBAP protocol provides the signalling service between the HNB and the HNB-GWrequired to perform HNB registration, UE registration, and error handling. More details are provided in 3GPP TS 25.469.

• RUA provides the signalling service between the HNB and the HNB-GW that is required to perform transparent transfer of RANAP messages, and error handling.More details are described in TS 25.468

Specific Stream Control Transfer Protocol (SCTP, Ref. IETF RFC 4960 ) configuration requirements have been introduced:

• The payload protocol identifier (PPI) field in SCTP is set to the value 19 assigned by IANA for use with the RUA protocol. In addition, the value 20 is assigned for the PPI for HNBAP.

• The destination port number field in SCTP is set to the value 29169 assigned by IANA for set up of the common SCTP association in HNBAP and RUA.

Some changes to RANAP have also been defined, mainly to support the exchange of CSG related information.


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CSG – Closed Subscriber Group

More details on CSG requirements can be found in 3GPP TS. 22.011, 22.220.

The following slides summarize the main CSG related features and functionalities defined in Rel 8, focusing on:

• CSG based Access Control

• CSG subscription provisioning

• CSG identification

• CSG based (re)selection


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CSG vs. Legacy Closed Access

The major access control differences between legacy UEs/Femtos and Rel 8 UEs/Femtos for Closed Access Femtos are:

• A Rel 8 UE is able to identify a CSG cell (Rel 8 Femto will broadcast a CSG Identity).

• A Rel 8 UE will not automatically reselect to a CSG cell whose CSG ID is not part of the UE CSGwhite list.

Rel 8 Femtos must be configured with a different LAC than the Macro to support:

• Access Control for legacy UEs.

• Paging optimization for both legacy and Rel 8 UEs.

• Network based access control for Rel 8 UEs. Although Rel 8 UEs should likely (re)select only authorized CSG cells, access permissions will also be checked by the network at the time of registration.

More details on possible access control options are described in the following slides.


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CSG vs. Legacy Closed Access (continued)

With the introduction of CSG in Rel 8, the “Select-my-Femto” paradigm is finally supported: Rel 8 UEs can differentiate between authorized vs. non authorized Femtos.

In a simple scenario of residential Femtos where subscribers have access only to their “home” Femto, the allowed CSG list will contain only one entry. This eliminates the need for the UE to try to reselect and register to any other Femto, saving UE battery life.

If the UE CSG allowed list is not updated, or during manual selection, a Rel 8 UE can try to register to an unauthorized CSG cell. In this case, to avoid the legacy issues related to barring the entire Femtofrequency (can be risky in a single carrier deployment, where the carrier is shared between the Macro and the Femto) and/or marking the LAC as forbidden (thus making any re-used LAC inaccessible for 12 hours or 24 hours), a new registration reject cause can be used: #25: Not authorized for this CSG.

Upon receipt of registration reject cause #25, the UE will neither bar the frequency nor store the LAC in a forbidden LAC list. Defined actions for the UE are:

• If the CSG ID of the cell where the UE has been rejected is contained in the Allowed CSG list stored in the UE, the UE shall remove the CSG ID from the Allowed CSG list.

• The UE shall search for a suitable cell in the same PLMN.


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CSG List in the UE

Details on the USIM based CSG list are in 31.102. The CSG List will provide:

• PLMN-ID, CSG type indication (e.g., “home” or “campus”, in text or graphics format) , HNBname (text format), and CSG-ID. HNB name and CSG type are optional.

The maximum length of the UE CSG allowed list is variable, and depending on UE implementation.

3GPP TS 24.285 defines the Allowed Closed Subscriber Group (CSG) List Management Object (MO), used for (Open Mobile Alliance) OMA-based provisioning to the ME. The Allowed CSG List MO is compatible with the OMA Device Management (DM) protocol specifications, version 1.2 and upwards, and is defined using the OMA DM Device Description Framework (DDF).

Standard requiremetns on those CSG parameters are as follows:

• The CSG-ID is a fixed length 27-bit value (fulfilling the requirement of >125M CSG-IDs).

• HNB Name shall be coded in UTF-8 format with a variable number of bytes per character. The maximum length of HNB Name shall be 48 bytes.

• CSG Type contains either Text CSG Type or Graphic CSG Type or both the Graphic and Text CSG Types. When the CSG Type has a text component, the CSG Type shall be coded in UTF-8 format with a variable number of bytes per character. The maximum text length shall not exceed 12 characters in any language.


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CSG List in the Network

More details on the HLR stored CSG list and the exchange of CSG related information between MSC-VLR/SGSN and HLR can be found in 3GPP TS 23.008 (HLR subscriber data) and 29.002 (MAP protocol & messages).

Some requirements on the HLR CSG data (permanent subscriber data ) are as follows.

• If a mobile subscriber has a Closed Subscriber Group (CSG) subscription, the HLR/HSS shall store Closed Subscriber Group information, which is:

– A list of up to 50 CSG-IDs per PLMN, and

– Optional: For each CSG-ID, an associated expiration date (which indicates the point in time when the subscription to the CSG-ID expires).

An absent expiration date indicates unlimited subscription.

Upon updating the VLR or the SGSN, the HSS/HLR identifies the VPLMN and transfers the applicable CSG-IDs and expiration dates to the VLR or SGSN.


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CSG Access Control in the Network

Rel 8 standard rules about Network Access control for CSG cells state:

• For pre-Rel 8 UEs and/or Femtos, the HNB-GW SHALL perform access control, based on the available CSG Control List. A Rel 8 HNB can, optionally, perform access control.

• For Rel 8 onward CSG-capable UEs, access control SHALL be performed in Core Network.

The decision at the HNB-GW is taken during UE registration (see Appendix C for details):

• The HNB-GW checks the UE capabilities and the Registration Cause. If these indicate that CSGis not supported and that it is not an emergency call, or if the HNB does not support CSG, the HNB-GW shall perform access control for that UE; otherwise the HNB-GW shall accept the UEregistration and allocate a context-ID for the UE.

One issue with HNB or HNB-GW based access control is that an IMSI may not always be available on those entities. In this case, an Identity Request procedure must be triggered, causing the IMSI to be sent over the air. The HNB-GW may additionally utilize a CN assisted method (e.g., using the IMSIprovided in the COMMON ID message) to minimize security risks.


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CSG Related Broadcast Information

The following definitions apply to CSG broadcast parameters:

• CSG HNB: An HNB broadcasting a CSG Indicator and a specific CSG identity.

• Non CSG HNB: An HNB that does not broadcast either a CSG Indicator or a CSG Identity.

Rel 8 specifies only the UE behavior in the presence of CSG HNBs, while other cases are UE implementation dependent; for example, a UE can consider the cell to be open or a hybrid (if forward compatible with Rel 9).


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CSG Related Broadcast Information

At the physical layer, a CSG cell is identified by its carrier frequency (UARFCN) and Primary Scrambling Code (PSC). A set of PSCs could be reserved for CSG deployment and this reserved PSCrange may be signalled in system information. The PSC of a CSG cell belongs to the reserved PSCrange, if broadcast.

On the mixed carrier frequency shared by both non-CSG cells (Macro cells) and CSG cells, CSG cells broadcast system information in the PSC range reserved by the network for CSG cells. The non-CSGcells may also broadcast the reserved PSC range. The reserved PSC range is only applicable to the UARFCN within the PLMN where the UE received this information. The UE considers the last received reserved PSC range to be valid within the entire PLMN for the duration of 24 hours. The UEmay use the reserved PSC information for CSG cell search and (re)selection purposes, according to the UE’s implementation.

Macro cells and CSG cells may broadcast indications of one or more carrier frequencies used for dedicated CSG deployment. This information may be used by a UE to avoid unnecessary measurements on that frequency, even when cell measurement rules would require measurements of this carrier frequency. Indications of which carrier frequencies are dedicated to CSG-only deployment may be signalled in system information and are applicable only in the cell where this information is broadcast.


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CSG (Re)selection Procedures – Manual CSG selection

Both Manual and Automatic CSG (re)selection are defined from Rel 8. (Automatic mode is defined in the next slide.)

In Manual mode, the UE indicates to the user the list of available CSGs in the currently registered PLMN. The list of CSGs presented to the user is not restricted by the Allowed CSG list stored in the UE. After the user makes a selection, the UE camps on a cell with the selected CSG identity and may attempt to register with the associated PLMN.

On request of NAS, the UE shall scan all RF channels in the UTRA bands according to its capabilities to find available CSG IDs. On each carrier, the UE shall at least search for the strongest cell, read its system information, and report available CSG ID(s) belonging to the registered PLMN together with their “HNB name” (if broadcast) to the NAS. The search for available CSG IDs may be stopped on request of the NAS. If the NAS selects a CSG ID and provides this selection to the AS, the UE shall search for an acceptable or suitable cell belonging to the selected CSG ID to camp on.

Note: When the user selects an entry in the list, the UE selects any CSG cell among the ones with same CSG ID.


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CSG (Re)selection Procedures – Autonomous and Automatic Reselection

If the UE is set to CSG automatic (re)selection, the above rules apply for UE cell reselection (see 3GPP TS 25.304 for details).

For Femto search and measurement, in addition to legacy rules (based on broadcast measurement triggers), the UE can be implemented to search for Femtos autonomously, based on location data/information or Macro fingerprint signatures — in other words, when the UE is confident to be close to an authorized Femto.

On a mixed carrier, a UE may avoid measurements of any CSG cells that the UE knows are not allowed. For dedicated CSG carriers, a UE may avoid measurements of any CSG cells that the UE knows are not allowed on a dedicated CSG carrier (including not measuring the entire carrier, if not needed).

No new parameters are defined for CSG cell ranking. The same cell reselection parameters defined for the UTRA case are used for CSG cell ranking, if configured. The operator may configure the cell reselection parameters, such as Qoffset and Qhyst, to bias the reselection of CSG cells.

Note: For intra-frequency reselection, both Best Coverage and Femto priority configurations are possible. For inter-frequency reselection, implicit Femto priority is defined by Rel 8 standards. That is, the UE shall reselect to the authorized CSG cell if it is the strongest cell on that carrier, irrespective of serving frequency ranking or absolute priority settings.


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Femto Characteristic

In Release 8, the Minimum Performance Specifications (i.e., 25.104) are defined in generic terms and would apply to any cells: Femto, Pico, Micro, Macro. This may unnecessarily increase Femto cost to ensure that all MPS are met (such as frequency accuracy, sensitivity, etc.)


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Femto RF Characteristics

Examples of Tx requirements:

• Maximum output power (per antenna): 20 dBm with single Tx antenna, 17 dBm with two Txantennas (compared to 24 dBm for Local Area BS class).

• HNB output power requirement for protection of adjacent-channel operator (new for Home BS class).

• Frequency error ±0.25 ppm (compared to ±0.1 ppm for Local Area BS class).

Examples of Rx requirements:

• Dynamic range: HNB dynamic range has been extended up to an interfering signal level of -39 dBm, with a desired signal level of -57 dBm.

• ACS: HNB adjacent channel selectivity requirement has been extended up to an interfering signal level of -28 dBm, with a desired signal level of -91 dBm.

Performance requirements:

• Similar to Local Area BS class except that large delay spread and high velocity channel models do not apply to HNBs.

HNB Interference Aspects are documented in TR 25.967, “FDD Home NodeB RF Requirements Work Item Technical Report”


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Hybrid Access Mode

Rel 9 defines a new type of Femto (in terms of access mode) called Hybrid Femto.

A Femto configured in Hybrid Access Mode provides services to its associated CSG members and to non-CSG members.

Three type of Femtos can be distinguished by a Rel 9 UE, based on Femto broadcast information:

• Open: no CSG-ID and CSG indicator (both absent)

• Hybrid: CSG-ID present and CSG indicator absent

• Closed: CSG-ID and CSG Indicator are both present

Few requirements are defined to differentiate Member vs. non-Member UEs in hybrid cells:

• In hybrid access mode, when services cannot be provided to a CSG member due to a shortage of H(e)NB resources, it shall be possible to continue the established communication of non-CSG members in another cell.

• In hybrid access mode, to minimize the impact on CSG members from established communication of non-CSG members, it shall be possible for the network to reduce the data rate of established PS communication of non-CSG members.


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Proximity Estimation/Indication

If, using autonomous search procedures, the UE determines that it is near a CSG or hybrid cell whose CSG ID is in the UE’s CSG white list, the UE may provide an indication of proximity to the SRNC. The CSG proximity indication may be used as follows:

• If a measurement configuration is not present for the concerned frequency/RAT, the SRNCmay configure the UE to perform measurements and report on the concerned frequency/RAT.

• The SRNC may determine whether to perform other actions related to handover to HNB/HeNBs based on having received a proximity indication (for example, the SRNC may not configure Compressed Mode gaps for the UE to detect the HNB/HeNB on a different frequency/RAT unless it has received a proximity indication).

Confusion-free Femto Hand-in

PSC/PCI confusion is resolved by the UE reporting the cell identity of the target HNB/HeNB.

No measurement gaps are required to read the MIB/SIBs of an intra-frequency cell. For inter-frequency/RAT target cells, the UE does use autonomous gaps; that is, the UE may suspend reception and transmission with the SRNC (delay requirements are not currently specified).

Access Control is performed based on UE reported membership status and SRNC validation.


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Intra-frequency Femto Hand-in Signaling Flow

1. The SRNC configures the UE to report “CSG Proximity detection”.

2. Based on autonomous search procedures, the UE sends an “entering CSG proximity” indication when it determines it may be near a cell whose CSG ID is in the UE’s CSG white list.

– UE can send a “leaving CSG proximity” indication if no longer near the reported cell.

3. If a measurement configuration for CSG/hybrid cells is not present, the SRNC configures the UE with relevant measurement configuration which includes the PSCs that the UE must measure and the PSCs for which SI acquisition should be performed. The network may use the CSG proximity indication for intra-frequency to minimize the time during which measurements for CSG/hybrid cells are configured.

4. In response to a trigger such as intra-frequency event 1d, the UE sends to the SRNC a measurement report that includes the measured PSC, Cell Identity, and CSG membership indication of the target HNB. The UE can acquire the MIB and SIB3/SIB4 of intra-frequency target HNB cells in parallel with reception of the serving cell transmissions in CELL_DCH. No measurement gaps are required for reading MIB and SIB3/SIB4.

5. The SRNC can then proceed with the handover.

The SRNC can request SI acquisition and reporting for any PSC, not just CSG/hybrid cells.


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Inter-frequency/RAT Femto Hand-in Signaling Flow

1. The SRNC configures the UE to report “CSG Proximity detection”.

2. Based on autonomous search procedures, the UE sends an “entering CSG proximity” indication when it determines it may be near a cell whose CSG ID is in the UE’s CSG whitelist. The CSGproximity indication includes the RAT and frequency of the cell.

– UE can send a “leaving CSG proximity” indication if no longer near the reported cell.

3. The SRNC configures a periodic measurement on the concerned frequency/RAT to measure CSG/hybrid cells. Compressed Mode gaps, if required by the UE, are also activated.

4. The UE sends a measurement report including the measured PSCs/PCIs.

5. The SRNC configures the UE to perform SI acquisition and reporting of a set PSC/PCI.

6. The UE performs SI acquisition using autonomous gaps, that is, the UE may suspend reception and transmission with the SRNC.

7. The UE sends a measurement report including Cell Identity and CSG membership to the network.

8. SRNC can then proceed with the handover processing.

The SRNC can request SI acquisition and reporting for any PSC, not just CSG/hybrid cells.

More handover processing details can be found in 3GPP TS 25.467.


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Operator CSG Allowed List

In addition to the Allowed CSG list defined in Rel 8, which is modifiable by both user and operator, Rel 9 defines a new list that is exclusively under the control of the operator.

The UE shall maintain both the Allowed CSG List and the Operator controlled list. The combination of both these lists is called the CSG white list. This list shall be stored on the USIM (if supported) or in a non-volatile memory in the ME. The USIM list has priority over the ME list.

All CSG cells belonging to a CSG identity that are not included in the Allowed CSG List or the Operator CSG list shall be considered not suitable by the UE.

For Manual CSG selection, an indication shall be given to the user as to which of the available CSGs is contained in the Allowed CSG List or the Operator CSG list. The available CSGs shall be displayed in the following order:

• CSGs whose CSG Identities are contained in the Allowed CSG list.

• CSGs whose CSG Identities are contained in the Operator CSG List.

• Other CSGs whose CSG Identity is not included in the Allowed CSG List or the Operator CSGlist.


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Inter-PLMN Manual CSG selection

When a user manually selects a CSG in a PLMN that is different from the last registered PLMN, the following rules apply:

• The UE shall enter into Manual PLMN Selection state.

• The UE shall attempt to register to the PLMN. This PLMN shall not be stored as the Last Registered PLMN.

• When the UE is no longer in the service area of the CSG, the UE shall return to the previous PLMN Selection state.

Temporary CSG Membership

For temporary members, it shall be possible to limit the period of time during which the subscriber is considered a member of a CSG (granted access rights); that is, it is possible to configure a time period for each temporary member.

The time period shall be configurable by the CSG manager and/or the operator operating the CSGand shall span from 1 decihour (0.1 hour, or 6 minutes) to several days. Unlimited membership to the CSG is allowed.

The CSG membership expiration timer is exchanged across network entities, but no mechanism is currently defined to inform the UE about it.


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Comments/Notes


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Section 8: Appendices

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PLMN Selection changes

Details can be found in 3GPP TS 23.122.


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Cell (re)selection Changes

Details can be found in 3GPP TS 25.331 and 25.304.

MBMS changes in Rel 6 are not considered here.


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Cell (re)selection changes

Details can be found in 3GPP TS 25.331 and 25.304.

MBMS changes in Rel 6 are not considered here.


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Femto Rel 8 Requirements

All service requirements for Femto are defined in 3GPP TS 22.011.

Below are some of the major requirements:

• Mechanisms shall be specified for an HNB to control access (accept and reject connection requests) of pre-Release 8 UEs. Such mechanisms may be different for those used to control access for a Release 8 UE.

• The operation of an HNB shall not adversely impact the performances of pre-Release 8 UEsoperating in the area where the HNB is active, and vice versa.

• The total bandwidth from the HNB toward the network for 4 simultaneous TS11 or TS12, including signaling and overhead, shall not exceed 200 kbps.

• Femto operation requirements, including:

– HNB installation

– HNB identification

– HNB location requirements

– Mobility

– Access control

– UE display

More details are described in the next slides.


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Rel 8 Femto Installation Requirements

The above requirements are defined in 3GPP TS. 22.011.


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Rel 8 Femto Identification & Display Requirements

The above requirements are defined in 3GPP TS. 22.011. More detailed requirements are summarized below.

CSG Type Display

The CSG Type shall be in a human readable form. It shall be possible to store the CSG Type in the USIM in text and/or graphic format. When the CSG Type has a text component, the CSG Type text length shall not exceed 12 characters in any language.

The CSG Type may be stored optionally in the ME. If the CSG Type is present in the USIM, the CSGType in the ME shall be ignored. It shall be possible to associate CSG Type to the CSG identities in the CSG white list.

HNB Name

The HNB Name length shall not exceed 48 x 8 bits.

Notes

• To support maximum flexibility in how the HNB Name is configured in any language, UTF-8 coding should be used. This allows a maximum length of 48 characters coded on one byte, 24 characters on two bytes, 16 characters on 3 bytes down to a minimum of 12 characters if all characters are encoded on 4 bytes.

The HNB Name may be stored in the USIM. If the HNB Name stored on the USIM is available, it shall take precedence over the broadcasted HNB Name.

The HNB Name may be stored optionally in the ME. If the HNB Name is present in the USIM, the HNB Name in the ME shall be ignored.

• The HNB Name is necessary to help the user choose the correct CSG identity when performing a manual CSG identity selection.


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80-W2703-1 Rev A


Rel 8 Femto Mobility Requirements

Some general performance requirements are defined.

Idle mode hand-in

The reselection should balance battery power consumption against performance, but shall have comparable performance to a cell reselection between two non-CSG cells where no neighbor cell information is provided by the network.

Idle mode hand-out

The reselection shall have the same performance as a cell reselection between two non-CSG cells, if network assistance is available. If network assistance is not available, the cell reselection performance shall be the same as cell reselection to a CSG cell.


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80-W2703-1 Rev A


Rel 8 Femto Manual Selection Requirements

More details are in 3GPP TS 22.011 and 23.122.


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80-W2703-1 Rev A


Rel 8 Femto Access Control Requirements

More details are in 3GPP TS 22.011, 25.304 and 23.122.


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80-W2703-1 Rev A


Notes


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80-W2703-1 Rev A


UE Registration for CSG UEs and CSG Femtos

1. Upon camping on the HNB, the UE initiates an initial NAS procedure (e.g., LU procedure) by establishing an RRCconnection with the HNB. UE identity and UE capabilities are reported to the HNB as part of the RRC Connection establishment procedure.

2. The UE transmits an RRC Initial Direct Transfer message carrying the initial NAS message (e.g., Location Update Request message) with some form of identity (e.g., IMSI or TMSI).

3. The HNB checks the UE capabilities provided in step 1 and, if these indicate that CSG is supported and if the identity of the UE (provided during RRC Connection establishment) is unknown at the HNB being accessed (no Context ID exists for the UE), the HNB initiates UE registration toward the HNB-GW (steps 4-6). If the HNB has a context ID for the UE, the UE registration procedure is not performed. No identification procedure is triggered, independent of the identity reported by the UE during RRC Connection establishment.

4. The HNB attempts to register the UE on the HNB-GW by transmitting the UE Register Request.

5. The HNB-GW checks UE capabilities and, if these indicate that CSG is supported and if the HNB supports CSG, the HNB-GW shall accept the UE registration and allocate a context ID for the UE.

6. The HNB-GW responds with a UE Register Accept message back to the HNB, including a context ID allocated to the UE.

7. The HNB sends an RUA Connect message containing the RANAP initial UE message.

8. The reception of the RUA Connect message at the HNB-GW triggers the set up of an SCCP connection by the HNB-GWtoward the CN. The HNB-GW then forwards the initial UE message including the CSG ID of the HNB.

9. The CN responds with an SCCP Connection Confirm message.

10. The CN may optionally perform Mobility Management procedures (e.g., Authentication procedure).

11. The CN performs access control of the UE.

12. After being granted access, the UE continues with the NAS procedure (e.g., Location Update procedure) toward the CN, via the HNB and the HNB-GW.


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80-W2703-1 Rev A


UE Registration for non-CSG UEs or non-CSG Femtos

1. Upon camping on the HNB, the UE initiates an initial NAS procedure by establishing an RRC Connection with the HNB. UE identity, UE capabilities, and Establishment Cause are reported to the HNB as part of the RRC Connection establishment .

2. The UE transmits an RRC Initial Direct Transfer message carrying the initial NAS message (e.g., LU Request)

3. The HNB checks the UE capabilities provided in step 1 and, if these indicate that CSG is not supported, or the HNBitself does not support CSG, and if the identity of the UE (provided during RRC Connection establishment) is unknown at the HNB being accessed (no Context ID exists for the UE), the HNB initiates UE registration toward the HNB-GW(steps 5-7). Before starting the UE Registration procedure, the HNB triggers the Identification procedure asking the UE for its IMSI (if not provided during the RRC Connection establishment). This procedure is not done for emergency calls. If the HNB has a context ID for the UE, the UE registration / identification procedures are not performed.

4. The HNB may optionally perform access control based on the provided IMSI and the provided access control list.

5. The HNB attempts to register the UE on the HNB-GW by transmitting the UE Register Request message, which contains at a minimum: UE identity, UE capabilities. and Registration Cause.

6. The HNB-GW checks the UE capabilities and the Registration Cause. If these indicate that CSG is not supported and that it is not an emergency call, or if the HNB does not support CSG, the HNB-GW shall perform access control .

7. If the HNB-GW accepts the UE registration attempt, it shall allocate a context ID for the UE and respond with an HNBAP UE Registration Accept message, including the context ID, to the HNB. If the HNB-GW chooses not to accept the incoming UE registration request then the HNB-GW shall respond with an HNBAP UE Registration Reject message.

8. The HNB sends an RUA Connect message containing the RANAP initial UE message.

9. The reception of the RUA Connect message at the HNB-GW triggers the set up of an SCCP connection by the HNB-GWtoward the CN. The HNB-GW then forwards the RANAP initial UE message to the CN.

10. The CN responds with an SCCP Connection Confirm message.

11. The UE continues with the NAS procedure (e.g., LU procedure) toward the CN, via the HNB and the HNB-GW.

NOTE: The HNB-GW may additionally utilize a CN assisted method (e.g., using the IMSI provided in the Common ID message) to alleviate the security risks associated with transmitting the IMSI over the air.


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80-W2703-1 Rev A


Notes


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80-W2703-1 Rev A


Reference Specifications (Rel 8)

• TS 22.011: “Service accessibility”

– General requirement of HNB Support: access control, Idle mode operation, service support

• TS 23.122: “Non-Access-Stratum functions related to Mobile Station (MS) in idle mode”

– Manual and automatic CSG selection at NAS level

• TS 24.008: “CN protocol, stage 3”

– CSG related NAS behavior

• TS 24.285: “Allowed CSG MO”

– Complete description on Allowed CSG Managed Objects

• TS 25.367: “Mobility Procedures for Home NodeB; Stage 2 Overall Description”

– Stage 2 agreements for CSG idle mode cell (re)selection features

• TS 25.331: "Radio Resource Control (RRC); protocol specification“

– Specification of Information Elements broadcast for CSG cell (re)selection procedures

• TS 25.304: “UE procedures in idle mode and for cell reselection in connected mode”

– Specification of Information Elements broadcast for CSG cell (re)selection


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80-W2703-1 Rev A


Reference Specifications (Rel 8)

• TS 25.467: “UTRAN architecture for 3G Home NodeB; Stage 2”

– Architecture, procedures, networking and OAM for HNBs

• TS 25.468: “UTRAN Iuh Interface RUA signalling”

– Transport protocol for RANAP (Iu signalling) over Iuh.

• TS 25.469: “UTRAN Iuh Interface HNBAP signalling”

– Signalling protocol for Iuh

• TR R3-020: “Home (e)NodeB; Network aspects (Release 8)”

– Stage 2 report of various HNB solutions for further consideration in RAN3

• TS 25.104: “Base Station (BS) radio transmission and reception (FDD)”

– Rx, Tx, and performance requirements for HNBs

• TS 25.141: “Base Station (BS) conformance testing (FDD)”

– Conformance tests for HNB Rx, Tx and performance requirements

• TR 25.967: “FDD Home NodeB RF Requirements Work Item Technical Report”

– Interference management analysis and algorithm recommendations for HNBs

• TR 33.820: “Security of H(e)NB”

– Security analysis, requirements and methods for future H(e)NBs (i.e., Rel 9)


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80-W2703-1 Rev A


Reference Specifications (new in Rel 9)

TS 22.220: “Service requirements for Home Node B (HNB) and Home eNode B (HeNB)”

- Defining the service requirements for Rel 9 H(e)NBs

TS 23.232: “IMS aspects of architecture for Home Node B (HNB)”

- Covering architectural requirements for IMS over H(e)NB

TR 23.830: “Architecture aspects of Home Node B (HNB) / Home enhanced Node B (HeNB)”

- Studying possible enhancements for H(e)NB in future releases (i.e, Rel 10)

TS 33.320: “Security of Home Node B (HNB) / Home evolved Node B (HeNB)”

- Covering security enhancements agreed for Rel 9


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123518886-Femto-Cells

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