01_ra20201en30gla0_bss network configuration and interfaces.pdf

8/11/2019 01_RA20201EN30GLA0_BSS Network Configuration and Interfaces.pdf

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BSS Network Configuration and Interfaces




Nokia Siemens NetworksAcademy

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Module Objectives

After completing the module, the student will be able to:

• Locate the BSS within the GSM System

• Analyze different BSS topologies

• List BSS Network Elements and their Functions

• Recall different BSS Interfaces

• Briefly introduce IP transmission features:

– A over IP

– Packet Abis

• Exercise: Label a diagram of the elements and interfaces used

within the BSS




GSM Network Subsystems

Control flowUser 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

CORE

(CS + PS) BSSMobile Station


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BSS Network Elements

OSS

MSC

SGSN

BSCTCSM

BTS

BTS

BTS

MS

BSS



3GPP Release 4 – CS Core Network Elements

OSS

MGW

SGSN

BSCTCSM

BTS

BTS

BTS

MS

BSS

MSS



MGW

BSS Network Elements with combined TCSM

OSS

BTS

BTS

BTS

MS

BSS

SGSN

MSS

STM1/OC-3 or IP

Remote BSC

Combi Transcoder + BSC

STM1/OC-3 or IP




Ater inside MGW Functionality

OSS

MGW

SGSN

BSC

BTS

BTS

BTS

MS

BSS

MSS




BSS Network Elements Functions (1/3)

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 CommonControl 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 de-interleaving 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 BSC





Transcoder

- 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




BSS interfaces using E1/T1

MSC

A i f Ater i f Abis i f Air i f

Gbi f

TCSM BSC

ET

ET

ET

ET

ET

ET

ET

ET

ET ET ETET

BTS

SGSN

MS

ET

E1/T1




BSS interfaces using STM-1/OC-3

MSC

Aif Abisi f Air i f

Gbi f

Combi TCSM BSC

SET SET

BTS

SGSN

MS

STM-1/OC-3

SET

SET

SET

SETSET

SET

SET

SET

SET




BSS interfaces using IP

MSC

Ai f Ater i f Abisi f Air i f

Gbif (FR)

TCSM BSC

ETIP

ETIP

ETIP

ETIP

ETIP

ETIP

ETIP

ETIP

ETIPETIP ETIP

ETIP

BTS

SGSN

MS

ETIP

IP

•Circuit emulation Service over Packet Switch Network: CESoPSN

• Available in RG10.




BSS interfaces: A interface over IP, Transcoder in BSS

MGW


TCSM BSC

ETP-A

BTS

MS

•Transcoder function located in BSS.


•The Transcoder is the “A over IP” termination point.

LegacyAbis

IP based Interface

TDM based Interface

PacketAbis

ETP-AA over IP




BSS interfaces: A interface over IP, Transcoder in MGW

MGW

Ater i f Abisi fAir i f

BSC

ETP-A

BTS

MS

•Transcoder function located in the MGW.


•The BSC is the “A over IP” termination point. •Only Packet Abis is supported in this case in S15

IP based Interface

TDM based Interface

PacketAbis

ETP-AA over IP

Only Packet Abis can beused in this

case!!




Dynamic Abis today

D y n a m i c A b i s

T D M l i n

e

M a n y d e d i c a t e d

T r a f f i c c h a n n e l s

CS

PS

O&M

SIG

Unused

• Each voice channel is allocated to a dedicated air interface channel

Legacy TDM PWE CESoPSN

P WE p a c k e t h e a d er



• PWE transports timeslots snapshots (empty or not)• Constant bandwidth need!!

• Some savings can be achieved (unallocated timeslots by configuration)

P k Abi l ll ffi




Packet Abis pools all traffic types

• TDM: All timeslots/E1 are pooled single “bit-pipe” … similar to Ethernet media

• No dedicated bandwidth reserved• TRAU framing and bit stuffing removed

• No empty packets are sent (Unused, silence …)

P a c k e t A b i s

o v e r T D M

T D M l i n

e

O n e T r a f f i c

c h a n n e l

CS

PS

O&M

SIG

Unused

Almost same packets in Packet Abis solution over TDM and over Ethernet options

P a c k e t A b i s h e a d er






BSS i t f P k t Abi IP/Eth t




BSS interfaces: Packet Abis over IP/Ethernet

MGW


TCSM BSC FLEXI BTS

MS

•The Packet Abis solution removes the traditional TDM Abis structure, where thestatic relationship between the Air and the Abis Interfaces is eliminated.


IP based Interface

TDM based Interface

PacketAbis

Legacy Aor

A over IP ETP

BSS i t f P k t Abi TDM




BSS interfaces: Packet Abis over TDM

MGW


TCSM BSC FLEXI BTS

MS

•This fully integrated feature enables the transport of Abis information using native IPover Time Division Multiplexed (TDM) Networks.


IP based Interface

TDM based Interface

PacketAbis

Legacy Aor

A over IP ETP SET

BSS I t f IP R d




BTS

BSC

TCSM /TRAU

NetActTM

Abis

AterA

O&M

SMLC

Lb+

BSC

BSC-BSC

BSS Interfaces over IP - Roadmap

Core Site

SGSN

MSS

MGW

Gb

Sigtran

Before BSS13 BSS13

(CESoPSN)

RG20

Packet Abis

A over IP

RG10

(CESoPSN)

Abis

BSS

A




Appendix:- Multiple A interface- Multiple Gb interface- Local Switching Function

Multipoint A IF Purpose & Benefits




Multipoint A IF- Purpose & Benefits

Basic idea

One BSC connect to several MSC servers in order to:

• Increase the network performance in terms of scalability (easier capacity

expansion)

• Distributing the network load among the serving entities (MSS/MSC

resiliency, if one MSS/MSC fails, the whole BSC won’t be lost )

• Reducing the required signaling as the MS roams (less inter-MSC

Handover and less Location Update Request to HLR less signaling

load).

Multipoint A IF configuration example




Multipoint A IF configuration example

MSC-2

MSC-1

MSC-3

POOL-1 POOL-2MSC-7

MSC-8

POOL-3

Area 1

BSC

Area 2

BSC

Area 3

BSC

Area 4

BSC

Area 5

BSC

Area 6

BSC

Area 7

BSC

Area 8

BSC

PoolArea 1

PoolArea 2

PoolArea 3

MSC-5

MSC-4

MSC-6

Multipoint Gb Purpose & Benefits




Multipoint Gb – Purpose & Benefits

• Purpose of the Multipoint Gb feature:

– To provide the capability for a Radio Access Node (PCU or PCU pool) toconnect to several SGSNs

• Operator benefits:

– Improved scalability and fault protection in the core network which leads tosavings in capital expenditure

– In case of failures in the GPRS core, the network remains operational withreduced SGSN capacity

– Facilitation of core network element upgrades

– Help in maintaining revenue and increasing end-user service quality

– Use for load sharing as the BSC is connected to several core networkelements

Multipoint Gb-interface




Multipoint Gb-interface

PCU Pool

SGSN 1 SGSN 2 SGSN 3 SGSN 4

PCU 1 PCU 2

PCU 3 PCU 4

Principle of Local Switching




Principle of Local Switching

Signalling

Voice

L

S F

Speech Data is

Switched Locally

Signalling Data

remains Backhauled

allowing MSC to

remain in control of

the call

Note: Locally switching a call has no impact on charging, mobility or

measurements since the MSC remains in control of the call.

Local Switching for Packet Abis feature allows to transfer MS-to-MS voice callsoriginated and terminated by the same BTS without going through the controlling BSC:

Speech data is directly switched between the involved base stations, that is,two terminals are served by the same BTS (BCF) and the voice call can be switchedinternally by the BTS (BCF)

Signaling/PS data is transmitted through all network entities

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