CS 268 Project 1 Tutorial Presentation

LTE WLAN Interoperability

Presenters

Sagar ChandawaleSusmit Mogarkar

Prof. Melody MohCS 268 Project 1 Tutorial

Tutorial Outline

• Wireless Mobile Technology• LTE – Evolution, Features, Architecture,

Protocols• Current Issues & Possible Solutions• SON, Interoperability• LTE-WLAN• WLAN Architecture• Papers• Recent Developments• Applications• Future Challenges

Wireless Mobile Technology• Wireless Mobile Technology • 2G – Only Voice• 2.5G - Adding Packet Services: GPRS, EDGE• 3G - Adding 3G Air Interface: UMTS - Supports 2G/2.5G also -Handover between GSM and UMTS technologies• 3G Extensions (3.5G) -HSDPA/HSUPA -IMS -Inter-working with WLAN (I-WLAN)• Beyond 3.5G -LTE -SAE -Adding mobility towards I-WLAN and non-3GPP air

interfaces

How LTE evolved?• Need for PS optimized systems

-Evolved UMTS towards packet only system 

• Need for higher data rates-Can be achieved with HSDPA/HSUPA

 • Need for high quality of services

-Use of licensed frequencies to guarantee quality of services

-Always-on experience (reduces control plane latency)-Reduced RTT

 • Need for simplified Infrastructure

-Simplified architecture by reducing number of network elements

LTE Features• Related to services:

-Provides future advanced services for VoIP-High peak data rates – 100 Mbps DL, 50 Mbps UL-Low U-Plane/ C-Plane latency – transit time (< 10

ms); setup times (< 100 ms)-LTE uses the concept of bearer: an IP flow with

defined Quality of Service.

• Related to Radio Area Network (RAN)-Improved “cell-edge rates” and spectral efficiency

(e.g. 2-4 x Re16)-Improved inner cell average data throughputs

(MIMO)-Scalable Bandwidth – 1.25, 1.6, 2.5, 5, 10, 15, 20

MHz

LTE Features (cont..)

• Related to cost requirements: reduced CAPEX & OPEX-Less complex architecture -Backhaul capacity usage is economical, simplified and

unified transport (IP)

• Related to compatibility requirements-Supports cost-effective migrations with non-3GPP

technologies and legacy 3G technology

LTE – Architecture

• It Consists of 4 parts:1. Access Network (E-UTRAN) – UE, eNodeB2.Core Network (CN) – MME, SGW, HSS, PCRF,

PDN- GW, IMS3.Control-plane traffic (MME, HSS, PCRF)4.User-plane traffic (UE, eNodeB, Serving

Gateway, PDN Gateway, IMS)

LTE – Architecture (Cont..)

Fig 1 [11]

LTE Protocol Architecture: User Plane

Fig 2 [12]

Protocol Architecture: Control Plane

Fig 2.1 LTE System Architecture [9]

Fig 3 [12]

LTE Physical Layer

•Modulation/Multiple Access

-Downlink: OFDM / OFDMA

-Uplink: SC-FDMA 1. A FFT-based transmission scheme like

OFDM2. Better Peak-to-Average Power Ratio3. Total BW is divided into small

frequency blocks for UE (15 blocks for 5 MHz BW)

LTE PHY – Multiple Antennas

• Minimum antenna requirement: 2 at eNodeB, 2 Rx at UE

• Beam forming used to improve throughput at cell edge

• Spatial Multiplexing using MIMO

• Multiple parallel uncorrelated paths ( Nt x Nr) to increase data rate

• Uses Space Frequency Block Codes - SCBC (a frequency-domain version of the STBC)

LTE MAC Layer (Media Access Control)

1. Maps Logical channels to Radio Channels

2. Multiplexes/Demultiplexes MAC SDU

3. Scheduling of resources

4. error correction using HARQ (Forward Error Correcting (FEC) + ARQ Error-control)

5. Transport format selection

MAC Layer Diagram

Fig 4 [14]

LTE RLC Layer (Radio Link Control)

•Segmentation and reassembly and error correction functions using ARQ

•Reformats PDCP PDU

•Reorder the out-of-sequence MAC PDU

LTE RLC Layer (Cont..)

Fig 5 [14]

PDCP Layer(Packet Data Convergence Protocol)• Data Transfer

• Header compression using RoHC algorithm

• Ciphering in both User & Control-plane

• Integrity protection of the control-plane

• Every radio bearer has one PDCP

• Handover support

PDCP Layer (Cont..)

Fig 6 [14]

Radio Resource Control (RRC)

Main aspects of Control Plane

•RRC (When the UE is in Idle mode)1. Cell Selection2. Reselection3. Paging Procedures

Radio Resource Control (RRC) (Cont..)

• RRC (When the UE is in Connected mode) – According to 3GPP TS 36.331

1. Broadcast of system information eg. Cell selection info, common channel configuration info

2. Inter-RAT Mobility/handover including security activation

3. Establishment, modification and release of radio bearers

4. Measurement reporting5. Support for self-configuration and self-

optimization6. RRC Connection control like Paging and QoS

control

Handovers in LTE

Scenario 1: 1. Inter-eNodeB handover – UE Leaving out from

the cell site

Fig 7 [15]

Handovers in LTE (Inter-eNodeB Handover)

2. Inter-eNodeB handover – UE coming to the cell site

Fig 8 [15]

Handovers in LTE (Intra-eNodeB Handover) Scenario 2:3. Intra eNodeB Handover in same E-UTRAN: UE

leaving out of the sector

4. Intra eNodeB Handover in same E-UTRAN: UE coming into the sector

Fig 9 [15]

Current Issues and Possible Solutions

• Congestion Control

• Coverage Issues

• LTE roll-out or country-wide deployment expenditures

• Power Consumption of LTE powered devices

Congestion Control:

• Packet loss, jamming, delivery delay

• Smart devices – voice/video/data

• No help from high data rates & high BW

• Cisco Virtual Networking index (VNI) forecast –

mobile data traffic x 2 till 2014

• AT&T data volume surged 8,000 % from 2007 to 2010

Coverage issues in LTE

• Scattering, Fading, Reflection, Refraction

• Urban Areas – obstacle causes call drop &

disturbance or noise during phone call

• dead spots

LTE roll-out/country-wide Deployments Expenditures

• LTE – new technology

• Huge investments – Risk in technology transformation

• Verizon Wireless – 1st to deploy LTE

• $8.9 billion total CAPEX in early 2011

• Roll-out Steps

1. Deployments

2. Post-commissioning

3. Trouble-shooting & Maintenance procedures.

Power Consumption

•Smart phones – high battery consumption

•66% of battery utilized by 3G enabled phones – downloading data

Improving TCP Performance

•Issues during Handover

-More bytes(packets) transmitted in the network during handover

-Causes TCP timeout at the transmitter-Causes handover quality to degrade

TCP Congestion Control•Sender receives network congestion

-Loss event is occurred due to timeout or 3 Duplicate ACKS

-Sender Limits the sending rate-Congestion Window

•Algorithm between congestion and rate-Two state: slow start, congestion avoidance-Two variable: Congestion window, threshold-

Congestion avoidance in TCP

•TCP Reno

Fig 10 [16]

LTE Intra eNodeB Handover

Fig 11A [7]

LTE Intra eNodeB Handover (Cont..)

Fig 11A [7]

Performance Analysis• Difference between ideal case and timeout occurrence

Fig 11B[7]

Congestion window fluctuation Analysis•In Optimal Case

Ref. [7]

Congestion window fluctuation Analysis (Cont..)•In Window halving state

Ref. [7]

Congestion window fluctuation Analysis (Cont..)•In Timeout state

Ref. [7]

Possible Solutions

1. Better Congestion Control 

-Improving TCP performance during intra LTE handover

-Techniques:1. Forwarding Avoidance

- Fast Path Switch- Handover Prediction

 2. Active Queue Management

Fast Path Switch Modification to LTE Handover

Fig 12 [7]

Possible Solutions (Cont..)

2. Traffic Management – Self organization networks (SON)

- Automatic Neighbor Relation

- PCI Planning

- Load Balancing

- Handover optimization

- Inter-cell interference co-ordination

Possible Solutions (Cont..)

3. Data Offloading techniques

- Femtocells cellular network at small level

- Interoperability with HetNets

- Interoperability pairs

1. LTE/Wi-Fi

2. LTE/WiMAX

3. LTE/3G and other 3GPP technologies

Interoperability

WLAN

Fig 13

[14]

WLAN Features & Architecture

• IEEE 802.11 standard

• 802.11b oldest – 11Mbps (no more used) works only on 2.4 GHz

frequency

• New – 802.11 a/g/n – Based on MIMO & OFDMA

• 802.11 a/g – 54 Mbps & 802.11n – 140 Mbps

• All are backward compatible

• Architecture – Wireless Nodes, BSS, AP, AAA/Proxy/Application

Server

WLAN Architecture

Fig 14 [13]

LTE-WLAN Interoperability

• Used for data offloading

• To improve coverage/load balancing

• WLAN access zone can be connected to core cellular network

• WLAN direct IP access – Subscriber charging, database and

authentication can be shared

• Services can be shared

• Service continuity – seamless handover

Interoperability between LTE-WLAN Scenarios:

• Non-roaming scenario

• Roaming Scenario

• Operator owned Wi-Fi hot-spot

• Aggregator provided Wi-Fi hotspot

UE#2

UE#1

WAG

PDG

AAA

S/P-GW

MME

eUTRAN

HSS

CSCF

VALWN AS

WLAN

LTE

IMS

Architecture for Voice over LTE-WLAN using IMS

Fig 15 [5]

Forward Rel Req

Call Flow

eUTRAN UE#2

MME PDG S/P-GW

UE#1

CSCF

VALWN AS

Registration Detect

Initiate HO

InformInviteOver Wi-Fi

Invite Update

-Release old session and completes new session-Remote leg update

Fig 16 [5]

Architecture for Voice over LTE-WLAN using IMS (Cont..)

• IMS (IP Multimedia Subsystem) acts as mediator

• Key blocks – AS, AAA, PDG, MME

• WAG – firewall to WLAN users

• AAA – proxy server used for authentication, authorization

and defines routes for PDG

• PDG – IP tunneling

• MME – handles mobility and handover procedures

Recent Developments - I

• VOLGA - Voice over LTE Generic Access was a failure!

-only backed up by T-Mobile

• Rest supported OneVoice – VoLTE

- promoting scalability

- reducing complexity

- enabling roaming

• LTE-Advanced

- Release 10 and beyond

- data rates 1 Gbps & 128 QAM

Recent Developments - II

Broadband evolved FEMTO (BeFEMTO)

- Relay of femtocells/mobile-femtocells

- For ubiquitous multimedia networks- Another goal is to achieve interoperability between femtocells/Wi-Fi Fig 17

Applications of LTE

•High-speed networks-Telepresence eg. Verizons' VGo-Video conferencing- Virtual conference & class room teaching

•Interoperability with Wi-Fi- office basements or factory floors- free hot-spots

Applications of LTE (Cont..)

• Remote Monitoring

- live feed from vehicle/home when away e.g. OnStar

- display traffic details

Future Challenges

• Managing risk in technology transformation

• LTE deployments with seamless mobility

• Inter-working of LTE with other 3GPP/non-3GPP

• Seamless handover between HetNets (802.21)

Thank You!

References[1] A White Paper, “LTE: The Future of Mobile Broadband technology”,

Verizon Wireless, 2009[2] White Paper, “Cisco Visual Networking Index: Global Mobile Data Traffic

Forecast Update”, Cisco 2009-2014[3] Ye (Geoffrey) Li, Jack H. Winters, Nelson R. Sollenberger, “MIMO-OFDM

for Wireless Communications: Signal Detection with Enhanced Channel Estimation”, IEEE transactions on communications, VOL. 50, NO. 9, Sept 2002

[4] Niranjan & Aruna Balasubramanian “Energy Consumption in Mobile Phones: A Measurement Study and Implications for Network Applications”, 9th ACM SIGCOMM conference, 2009.

[5] Jinho Hwang, Nakpo Kim, Yungha Ji, Jongseog Koh, “A Mobile VoIP Architecture over LTE & WLAN network”, Core N/W Development Team Mobile R&D Laboratory Personal Customer Group, 2010

[6] Guruprasad Naik, “LTE WLAN Interoperability for Wi-Fi Hotspots”, Communication Systems and Networks (COMSNETS), 2010 Second International Conference

References[7] D. Pacifico, M. Pacifico, C. Fischione, H. Hjalrmasson, K. H. Johansson,

“Improving TCP Performance during the Intra LTE Handover”, IEEE INFOCOM, 2009

[8] Broadband evolved FEMTO networks,” http://www.ict-befemto.eu/home.html”

[9] Verizon Wireless 'OnStar' LTE application, “http://news.vzw.com/news/2011/01/pr2011-01-04.html”

[10] Maria E. Palamara, “Realizing LTE: Understanding the Challenges and Planning for LTE Introduction”, Alcatel-Lucent, January, 2009.

[11] A White paper, “LTE Inter-Technology Mobility”, Motorola - 2008[12] Wired n Wireless, “http://wired-n-wireless.blogspot.com/2009/01/lte-

protocol-stack.html” , January 6, 2009. [13] Acquisition of T-Mobile USA, Inc. by AT&T Inc. “Description of

Transaction, Public Interest Showing and Related Demonstrations”, Filed with the Federal Communications Commission, April 21, 2011.

[14] Nicola Bui, Federico Guerra, “Long Term Evolution (LTE) an overview”, Department of Information Engineering – University of Padova – Italy

Back

References[15 ]Artiza Networks,”

http://www.artizanetworks.com/lte_tut_han_pro.html” , 2011[16] Kurose, Ross, “Computer Networking A Top Down Approach 5th

Edition, 2009[17] Broadband evolved FEMTO networks,”

http://www.ict-befemto.eu/home.html”

Non-Roaming Scenario

Fig 18

Roaming Scenario

Fig 19

Operator owned Wi-Fi hot-spot

Fig 20

Aggregator Provided Wi-Fi Hotspot

Fig 21