01 Rn28191en20gla0 Bss Overview

8/10/2019 01 Rn28191en20gla0 Bss Overview

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BSS overview (Review)RG20(BSS)


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Objectives

After this module the participants should be able to:

Label a diagram of the elements and interfacesused within the BSS

Describe the functions of the BSS elements

Describe RG20 transport features


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GSM subsystems

Control flow

User data flow

PSTN

PLMN

PSPDN

CSPDN

ISDN

PSTN Public Switched Telephone NetworkPSPDN Packet Switched Public Data Network

PLMN Public Land Mobile Network

CSPDN Circuit-Switched Public Data Network

ISDN Integrated Services Digital Network

OSS

NSS BSS Mobile Station

The GSM network is functionally divided into four elements. Base Station Subsystem

(BSS) is one of the main functional elements of the GSM network. The other elements

in the GSM network are the network switching subsystem (NSS), GPRS core networkto SGSN and network service and management subsystem (provided by NetAct).

The main function of the BSS is to connect the mobile subscriber's mobile station (MS)

to the GSM network and provide connections to the mobile switching centre (MSC), and

to GPRS core network, serving GPRS support node (SGSN). The BSS also takes care

of the mobility management of the cellular network including, for example, handover

management and various measurements.


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GSM subsystems

Network Switching Subsystem

Switching

Mobility Management

Connection

OSS

NSS

BSS

Base Station Subsystem

Radio Resource Management

Radio Link Management

Operation and Support System

Fault Management

Configuration Management

Performance Management


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Circuit-switched/Packet-switched services

Control flow

User data flow

PSTN

PLMN

SCN Switching Core Network

PCN Packet Core Network

OSS

SCNBSS

Mobile Station

PCNInternet

The Switching Core Network (SCN) comprises network elements that implement CSservices (e.g. voice calls), like Multimedia Gateway (MGW), Mobile switching centreserver (MSS).

Packet Core Network (PCN), on the other hand, supports PS data connections toexternal networks (e.g. Internet).


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BSS Network Elements

OSS

MSC orMGW/MSS

SGSN

BSCTCSM

BTS

BTS

BTS

MS

BSS

Transcoder, TCSM2

- considered as part of the BSC

- normally at the MSC site- used for converting the bit rate of

traffic channels between 64 and 16

kbit/s

- speech activity detection

- framing and synchronisation of the

vocoder block

- interfaces to the MSC / BSC

Base Station Controller, BSC

- terrestrial channel management

- configuration and management of traffic

channels

- frequency hopping control

- paging

- BTS and MS power control

- idle channel quality monitor

- quality and field strength control for active

channels

- handover control

- maintenance of BTS / BSC / TC

- interfaces to the NMS / BTS / TC / SGSN

Base Transceiver Station, BTS

- timing Broadcast Control Channels (BCCH) and Common Control Channels

(CCCH)

- forwarding MS and BTS measurements to the BSC

- detecting RACHs (Random Access Channels) from the MS

- channel coding and decoding on the radio path

- interleaving and deinterleaving on the radio path

- encryption and decryption on the radio path

- performing frequency hopping

- GMSK modulation, demodulation, up / down conversion and power amplifying

- transmitter RF signal combining

- receiver RF signal filtering, amplifying and multicoupling

- reporting idle traffic channel quality to the BSCTransmission Unit TRU

- provides Abis interface

- reallocates the Traffic and signalling channels in the BTS


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BSS interfaces

MSC

A Ater Abis Um

Gb

TCSM BSC BTS

SGSN

MS

MGW

AoIP(TC in MGW)

A interface

The interface between the mobile switching centre (MSC) or Multimedia Gateway

(MGW) and the base station controller (BSC) is implemented according to the GSMspecifications.

The Transcoder Submultiplexer (TCSM) is located normally at the MSC site, because

of the superior transmission savings possible with submultiplexing between the TCSM

and the BSC. A physical A interface used to consist of PCM lines or optical lines

between network elements. But with the introduction of the AoIP feature in RG20(BSS),

the A-interface between BSS and MGW can also be based on IP/Ethernet. There are

two scenarios for AoIP functionality:

1. AoIP Transcoder in BSSThe transcoder function is located in the BSS. The transcoder is the A over IP termination

point. The G.711/RTP/IP protocol is employed

The benefit for this configuration is that it utilizes existing transcoder capacity when

IP-connections in A-interface are used.

2. AoIP Transcoder in Core Network (MGW)

The transcoder function is located in the core network (that is, the 3G network architecture).

The BSC is the A over IP termination point. At the same time, the BSC

hides the mobility from the core network. The CODECx/RTP/IP protocol is

employed


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RN28191EN20GLA08 N okia Siemens Networks

IP/Eth E2E Connectivity - Evolution OverviewBefore BSS13 RG20

BTS

BSC

TCSM /TRAU

NetActTM

Abis

Ater

A

GbO&M

SMLC

Lb+

Sigtran

MGWMSCHLR

RG10

Integrated IP/ETH interfaces for Gb, BSC-BSC, LB+, Sigtran and O&M available today

Abis IP available today

Ater /Abis IP integrated for BSC3i and TCSM3i available today; external for legacy Standardized AoIP with RG20

All interfaces are capable for IP/ETH connectivity with todays plans

Packet Abis coming on TOP offering additional advantages

BSC

BSC-BSC

SGSN


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Abis/A/Ater over IP/Ethernet for Installed Base

2G BTS

Packet SwitchedNetwork

Packet transport convenience and cost

A-1200

Legacy BSC

A-2200

BSC3i 1000/2000

Flexi BSC

ETIP

IP /

Ethernet

IP /

Ethernet

Note: See alternative IP / Ethernet evolution in RG20:using Flexi EDGE System module (BSS21443)

Supports CESoPSN (PWE3) functionality

Multiple synchronization methods available

Media conversion from TDM to IP/Eth

A-2200 can also be applied to A/Ater-interface

E1/T1

E1/T1

RG10EP

Feature ID(s): BSS21481

A-1200 and A-2200 supports Synchronous Ethernet, Timing Over Packet IEEE 1588-2008


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RN28191EN20GLA010 N oki a S ie men s Ne tworks

A over IP

Feature ID(s): BSS21341, BSS30380

Simplified Multipoint A configurationGreater transport efficiency

The A-interface between BSS and MGW will be based on IP / Ethernet

Several scenarios are under discussion in 3GPP standardisation:

Transcoder in the BSS (G.711 / RTP / IP protocol)

Transcoder in MGW (CODECx / RTP / IP protocol)

Simplifies the system configuration in Multipoint A / Flexible A scenarios

Improved transport efficiency for the Transcoder in the MGW scenario throughstandardising TrFO for GSM/EDGE

A over IP introduces new interface plug-in unit in the BSC and TCSM ETP-A Exchange Terminal for Packet transport over A interface ETP-A is responsible for IP processing and packet-PCM conversion for interfacing with

the BSC switching network

Available for Flexi BSC, BSC3i 1000/2000 and TCSM3i Flexi BSC and BSC3i 2000 (two cabinets): 4 ETP-A cards

BSC3i 1000 (one cabinet): 2 ETP-A cards

TCSM3i RG20: 5 cards per cabinet, TCSM3i RG10 or older: 3 cards per cabinet When ETP-A is used for A over IP in stand alone TCSM3i, IP/Ethernet connection is needed between BSC and

TCSM3i for control functions

RG20

Benefits for the Operator: The key benefit arises from the CAPEX / OPEX savingsthat can be derived through employing IP networking. The flexibility of the solution isalso increased. Further, configuration is also simpler in Multipoint A type network

scenarios.With Transcoder in the BSS, the existing transcoder capacity can be used along withthe new IP-connectivity at the A-interface.

With Transcoder in the Core Network, voice quality is enhanced since tandem codingis no longer necessary and latency is also improved. A reduced transcoding capacityis required in the BSS (realised in the Core Network).

Functional Description: There are two architecture options:

1. The Transcoder function is located in the BSS (that is, the standard GSMarchitecture). The Transcoder is the A over IP termination point.

The G.711 / RTP / IP protocol is employed.

2. The Transcoder function is located in the Core Network (that is, the 3Gnetwork architecture). The BSC is the A over IP termination point. At thesame time, the BSC hides the mobility from the Core Network.

The CODECx / RTP / IP protocol is employed.

For the Transcoding in BSS scenario, the ETP-A module is required for the TCSM3i,which is managed from the BSC via Ethernet. For this configuration both A over TDMand A over IP are supported within the same TCSM3i. The Abis interface may beeither Packet Abis (requiring both the ETS2 and ETP modules) or Legacy Abis.

When transcoding is performed within the Core Network, then the Abis interfacemust be a Packet Abis type. Calls to Handsets on Packet Abis are routed on A overIP directly to the Core Network transcoder. Calls to Handsets on a Legacy Abis arerouted via the TCSM3i to the Core Network (as normal). A handover between aPacket Abis BTS and a Legacy Abis BTS is managed by the Core Network as anInternal Handover.


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A over IP implementation scenarios- Transcoder in BSS


Note:

UltraSite, BTSplus, MetroSite support legacy Abis

Flexi EDGE supports both legacy Abis and Packet Abis

1) Support availability needs to be confirmed from MGW-supplier

RG20

Packet / TDM conversion

TDMIPoTDM

IPoTDMBSC

Packet Abis

TDM TDM

Ater

Eth IPoEthIPoEth

Packet Abis

Eth/ETP

TDM/ETS2+ETP

Alternative interface

AoIP

(G.711)

TC in BSS

Eth/ETP-APWE PWE

TCSM

MGW 1)

Flexi EDGE

Flexi EDGE

Flexi BSC

BSC3i 1000/2000

TCSM3iTDM

TDMTDM

TDMLegacy AbisAvailablewithRG20

MGW


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A over IP implementation scenarios- Transcoder in MGW

Note:

BTS must be connected via Packet Abis to BSC

BTS connected through legacy Abis to BSC is not supported until RG30. Prioravailability of Legacy Abis support with AoIP and TC in MGW following options exist:

Parallel use of AoIP (TC in MGW) for Packet Abis traffic and Ater/AoIP (TC in BSS) for legacyAbis. Ater can utilize TDM or integrated IP/Ethernet (PWE3 CESoPSN).


RG20

TDMTDMTDM

TDMIPoTDM

IPoTDM

TDM

BSC

Packet Abis

Legacy Abis

Eth IPoEthIPoEth

Packet Abis

AoIP

(CodecX )

TC in MGW

AvailablewithRG20

Flexi EDGE

Flexi EDGE

Flexi BSC

BSC3i 1000/2000

RG30

candidate

BSS101407

Any vendors

MGW

MGW

TC

TDM/ETS2+ETP

Eth/ETPEth/ETP-A


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Packet Abis over IP/Ethernet

Significant OPEX Savingscombining optimized Abis and low cost Transport Media


Full BSS integrated Abis Optimization

Cost efficient transport media (Ethernet)

EDGE Phase II and OSC optimized

BSC

Eth Eth

RG20

Packet SwitchedNetwork

IP

Packet Abis

Ethernet

IP

Packet Abis

Ethernet

Flexi EDGE

Compared to traditional TDM Abis(for typical traffic scenario)

Bandwidth savings

up to ~50%

Summary:

This fully integrated feature enables the transport of Abis information using native IPover Packet Switched Networks (via Ethernet).

Benefits for the Operator:

The operator is able to employ Packet Switched Networks in order to provide thetransport backhaul for the Abis traffic, offering significant OPEX savings due to themore cost effective physical media (Ethernet) and the simplified operation andmaintenance of the network that can then be derived. In addition to the physicalmedia benefit, Packet Abis also offers significant bandwidth savings in comparisonwith traditional TDM- or PWE-based packet transport since it introduces a veryefficient and fully integrated Abis Optimization capability. The integrated AbisOptimization also facilitates the introduction of high bandwidth features such asEDGE Evolution and OSC without necessarily increasing the backhaul bandwidthcapacity requirement. Bandwidth can be shared by CS, PS and Signalling traffic.There are no predefined limitations except the total available bandwidth provided bythe physical link.

Functional Description:

The Packet Abis solution removes the traditional TDM Abis structure, where thestatic relationship between the Air and the Abis Interfaces is eliminated. Further, AbisOptimization through the removal of silence and idle frames, multiplexing andbandwidth sharing for the CS-Userplane; PS-Userplane; Control-Plane andManagement-Plane achieves significant bandwidth savings. If no data needs to besent then no capacity is occupied/utilised.

The Packet Abis U-Plane is transported over UDP/IP and the C-Plane/M-Plane istransported over SCTP/IP. The physical interface supported is Ethernet.


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Packet Abis over TDM

Feature ID(s): BSS21440, BSS21539 (related)

Full BSS integrated Abis Optimization

Packet Transport Efficiency on TDM

EDGE PhaseII and OSC optimized

BSC

RG20

TDM Network

MLPPP

IP

E1/T1/SDH

MLPPP

IP

E1/T1/FB

Flexi EDGE

Significant OPEX SavingsOptimized Abis while keeping the existing transport infrastructure

Bandwidth savings

up to ~55%

Compared to traditional TDM Abis(for typical traffic scenario)

TDM TDM

Packet Abis Packet Abis

Summary:

This fully integrated feature enables the transport of Abis information using native IP overTime Division Multiplexed (TDM) Networks.

Benefits for the Operator:The operator can utilise the existing installed TDM Infrastructure, easing the introduction ofthe Packet Abis solution.

Packet Abis over TDM offers significant bandwidth savings in comparison with traditional TDMtransport since it introduces a very efficient and fully integrated Abis Optimization capability.Bandwidth can be shared by CS, PS and Signalling traffic as transmission resources are usedas pools. Pooling results as reduced number of TDM lines or reduced bandwidth withMicrowave radios/SDH transmission. Resource overbooking is possible: TRX number canexceed transmission line nominal capacity. There are no predefined limitations except thetotal available bandwidth provided by the physical links. The integrated Abis Optimization alsofacilitates the introduction of high bandwidth features such as EDGE Evolution and OSCwithout necessarily increasing the backhaul bandwidth capacity requirement.

Functional Description:

The Packet Abis solution removes the traditional TDM Abis structure, where the static

relationship between the Air and the Abis Interfaces is eliminated. Further, Abis Optimizationthrough the removal of silence and idle frames, multiplexing and bandwidth sharing for theCS-Userplane; PS-Userplane; Control-Plane and Management-Plane achieves significantbandwidth savings. That is, if no data needs to be sent then no capacity occupied/utilised.

The Packet Abis U-Plane is transported over UDP/IP/MLPPP and the C-Plane/M-Planetransported over SCTP/IP/MLPPP. The physical interface supported is TDM.

Multiple E1 or T1 interfaces effectively provide virtual common bandwidth (larger pool) usingMLPPP. Packet Abis over TDM is supported by all existing Flexi EDGE BTS transport units,including e.g. FIFA and FIYA/FIQA units. As Packet Abis over TDM allows to reducetransmission capacity of individual BTS site this allows overbooking. Overbooking meansadding TRXs beyond transmission line nominal capacity.

Packet Abis IP/TDM Aggregation feature (BSS21539) allows to chain multiple BTS-sites andperform transmission aggregation/optimization (=reduction) at every chained site. This uniqueMultistage aggregation technique provides the most cost efficient TDM transmission option

on the market.


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BSS overview

RN28191EN20GLA01 5 N okia Si emen s Networks

Exercise: Network Elements and interfaces

BSS

01 Rn28191en20gla0 Bss Overview

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