7 - gg_sp003_e1_1 gb interface overview-30

8/12/2019 7 - GG_SP003_E1_1 Gb Interface Overview-30

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TN_BT006_E1_1

Gb interface overview

V1026


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Course Objectives

Gb Interface overview

NS

BSSGP

LLC SNDCP

Gb interface Data Flow


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Gb Interface

Gb interface connect SGSN and BSC. BSC add a PCU

(Packet Control Unit) to implement GPRS function

SMS-GMSCSMS-IWMSC

MSC/VLR HLR

BSS(BTS+BSC)

SGSN GGSNMTTE

SGSN

Other PLMN

GGSN

PDN TE

EIR

SM-SC

Signal Interface

G

b

U

m

R

G

n Gf

Gp

G

nGi

A

G

sGr

G

c

Gd D

E C

Signal and Transport interface


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Gb Interface Protocol StackControl Plane


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Gb Interface Protocol StackUser Plane


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Course Objectives


NS

BSSGP

LLC SNDCP



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NS Layer Position

L1

NS

BSSGP

LLC

L1

NS

BSSGP

RELAY

RLC

MAC

BSS SGSN

Gb


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NS Layer Inner Structure

Sub-Network Service /Sub-Network Service protocol

Network Service Control /

Network Service Control protocol

Network Service

FR (Frame Relay)


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NS Layer FunctionFR

Implement following function Receiving and sending of FR layer frames

Congestion statistics report


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NS Layer FunctionNetwork service

Control Sub-layer

Network Service control sub-layer provide non-confirmed data sending and receiving service for

upper layer upon PVC provided by FR ;

Provide load sharing upon effective PVC;

Provide link congestion indication for upper layer

by use of congestion report mechanism of FR,

link congestion recovery is done by FR layer;

Provide status indication for upper layer such asthe change of link transportation capabilities;


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NS Layer Basic Concept

BC BC is made up of a group of timeslots of one E1. The

two peering part of BC must use the same timeslots.

DLCI

PVC identification of FR layer NSVC

NS layer virtual channel in a BC, it is identified byNSVCI which is unique in SGSN

NSE NSE is the management entity of NS layer, one NSE

can manage the blocking/unblocking and resetting ofNSVC under this NSE.


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Relationship between NSVC and FR PVC

FR PVCBC,DLCI

NSVCNSVCI

PCU

FR Netwaork

SGSN

DTE

DTE

DTE

DCE


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Course Objectives


NS

BSSGP

LLC SNDCP



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BSSGP Layer Position

L1

NS

BSSGP

LLC

L1

NS

BSSGP

RELAYRLC

MAC

BSS SGSN

Gb


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BSSGP Service Model


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BSSGP Layer Function

BSSGP provide necessary radio information forRLC/MAC between BSS and SGSN

Provide management control function between

SGSN and BSS;

Provide data transfer function

Provide signal information transport function

Provide BVC status management function

Provide MS status management function;


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BSSGP Layer Parameter

BVCI BVC is the channel between BSSGP entities, there are

PTP BVC, SIG BVC and PTM BVC at BSSGP peer

layers

PTP BVC is responsible for user data transfer SIG BVC implements signal information transfer such

as PAGING. Each NSE corresponds to one SIG BVC

PCU assign a BVC entity for each cell and a BVCIthis

BVCI is transferred to SGSN to create cell list


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Difference between PTP BVC and SIG BVC

NSE NSE

NSVC1

NSVC2

SIG BVC

PTP BVC

Data flowSignal Flow

Signal

User Data

Cell 1 Cell 2Cell 1 Cell 2


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Traffic control mechanism

MS

L1

NS

BSSGP

LLC

BSSGP

BSS SGSN

GbUm

L1

NS

RELAYRLC

MAC

GSM RF

MAC

GSM RF

RLC

LLC


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Course Objectives

Gb Interface overview NS

BSSGP

LLC SNDCP



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LLC Layer Position

MS

L1

NS

BSSGP

LLC

BSSGP

BSS SGSN

GbUm

L1

NS

RELAYLCR

MAC

GSM RF

MAC

GSM RF

RLC

LLC


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LLC Layer Function

Provide point to point data transfer link betweenMS and SGSN;

Provide security transfer of user data by

encryption;

Logical link control function

Error recovery and report


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Course Objectives


BSSGP

LLC SNDCP



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SNDCP Layer Position

RLC

MAC

Relay

NetworkService

GTP

Applicatio

n

IP / X.25

SNDCP

LLC

RLC

MAC

GSM RF

SNDCP

LLC

BSSGP

L1bisGSM RF

BSSGP

L1bis

Relay

L2

L1

IP

Um GbMS BSS SGSN

NetworkService

UDP /

TCP


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SNDCP Layer Function

Multiplexing of different protocols Compression and uncompressing of user data

Compression and uncompressing of protocol

control information such as TCP/IP header

Segmentation and regrouping


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SNDCP basic functionprotocol

multiplexing model

SNDCP

Packet Data

Protocol

LLC

NSAPI

N-PDU

SAPI

SN-PDU

Packet Data

Protocol

Packet Data

Protocol

. . .


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SNDCP basic functionSegmentation

Mechanism

Segmentation of downside data sending SNDCP layer entity segment SNPDU

to make sure that the data unit length is less than

the length defined in LLC layer

Regrouping of upside data;

receiving SNDCP entity regroup original NPDU


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Course Objectives


BSSGP

LLC SNDCP



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Gb Data Flow Processing

S

G

S

P

Gn Process

module

Gb process

module

Data

flow

SNDCP

IMSI+NSAPI>PDP Context

Compression Segmentation

PDP context>MM context

LLC framing

Fix length Packet

CRC check Encryption

LLC frame

BSSGP

MM context

MS traffic

control

BVC

traffic

control

NSNSVC load

sharing

MM context

FR

NSVC>PVC

L1BSS

S

G

B

P


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7 - gg_sp003_e1_1 gb interface overview-30

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