GO_NA28_E1_1 (E)GPRS Signaling Flow & Test

7/28/2019 GO_NA28_E1_1 (E)GPRS Signaling Flow & Test

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(E)GPRS Signaling Flow & Test

ZTE university



Course Objectives

To be familiar with common (E)GPRS signaling flow

To be familiar with (E)GPRS test content

To master (E)GPRS test techniques



Contents

A Brief Introduction to (E)GPRS Signaling

Main (E)GPRS Signaling Flows

(E)GPRS Field Test

Main (E)GPRS Test Signaling Flow




(E)GPRS Signaling Protocol Stack

Relay

Network

Service

GTP

Application

IP/X.25

SNDCP

LLC

RLC

MAC

GSMRF

SNDCP

LLC

BSSGP

L1bisGSMRF

BSSGP

L1bis

Relay

L2

L1

IP

L2

L1

IP

GTP

IP/X.25

Um Gb Gn i

Network

Service

UDP/

TCP

UDP/

TCP

RLC

MACNetwork

Service

L1bis

MS BSS SGSN GGSN

GPRS Protocol Stack of Data

Transmission Platform




( (E)GPRS Signaling Protocol Stack

GPRS Protocol Stack of

Control Platform

Um GbMS BSS SGSN

GMM/SM

LLC

RLC

MAC

GSM RF

Relay

RLC

MAC

GSM RF

BSSGP

NetworkService

L1

LLC

BSSGP

NetworkService

L1bis

GMM/SM




GSM RF Protocol Physical layer can be divided into two sub-layers by

function—physical RF sub-layer and physical link sub-layer:

Physical RF sub-layer is used to modulate the bitstream sent from upper physical sub-layer and todemodulate the waveform coming from peer layer;

Physical link sub-layer provides information

transmission on the physical channel between MSand network, including: data delimitation, coding,error detection and correction, on physicalmedium.




RLC/MAC Protocol

RLC/MAC layer is a lower-layer data link layer. The functions for RLC/MAC

layer are as follows:

MAC

1. Provide effective multiplexing of UL/DL data and control signaling.

2. Provide contention solution, including conflict detection & recovery, for channel access initiated by MS.

3. Provide access scheduling, including the PS queuing, for the channel accessterminated by MS.

4. Priority processing.

RLC1. Provide interface primitives for transmitting LLC-PDU between LLC and MAC.

2. Segment LLC-PDU and reorganize it into RLC data block.

3. The reverse error correction process for the selective retransmission of incorrect data.




LLC ProtocolLLC layer, i.e. Logical Link Control (LLC) layer, is used to transmit

packet data between MS and SGSN.

Functions of LLC:

1. Provide one or more logical link connections through DLCI.

2. Sequence control, guaranteeing the sequence of frames on logicallink.

3. Check transmission, format and operation errors on logicalchannels.

4. Recover errors detected.5. Notification of unrecoverable errors.

6. Flow control.

7. Encryption




SNDCP (Sub-Network Dependent Convergence Protocol )Functions of SNDCP：

1. Multiplex many PDPs;

2. Compress/extract user data and protocol control information;

3. Segment N-PDU into LL-PDU or desegment LL-PDU intoN-PDU

Relay

The Relay in BSS is used to relay the LLC PDU between Um

interface and Gb interface. The Relay in SGSN is used to relay the

PDP PDU between Gb interface and Gn interface.




BSSGP (Base Station System GPRS Protocol )This layer transmits routing-related and QoS-related information

between BSS and SGSN, and does not perform error correction. In

BSS, this layer likes the interface between LLC and RLC/MAC.

NS (Network Service Layer)

Functions of NS:

1. Provide NS SDU transmission

2. Provide network congestion indication

3. Provide status indication, e.g. changes of usable transmissioncapacity




Different Parts of NS Protocol

NSCtrl (Functions of NS Control layer)

1. Provide NS SDU transmission

2. Load splitting

3. NSVC management, including block, unblock, reset, and test.

Functions of SNS (Functions of Sub-network Service)

1. Provide the access to intermediate transmission network, i.e. NSVL

2. Transmit data sequentially on NS-VC

3. Detect and report errors in protocol, and errors such as failure of

intermediate transmission network, equipment fault, and link failure,etc.




GTP (GPRS Tunneling Protocol)

This protocol supports data and signaling transmission between the supporting

nodes of GPRS backbone network. All PTP PDU PDP need be encapsulated

by GTP.

UDP/TCP

TCP carries the GTP PDU that need be supported by reliable data link (e.g.

X.25) in GPRS backbone network; UDP carries the GTP PDU that need not be

supported by reliable data link (e.g. IP). TCP provides flow control and protects

GTP PDU from being lost or damaged. UDP protects GTP PDU from being

damaged.

IP

It is a GPRS backbone network protocol applied to router user data and

control signaling. GPRS backbone network was based on IP version 4 protocol

initially, and will use version 6 finally.




One-phase Access onPBCCH

Contention Solution

After receiving UL assignment

message, MS must send three RLC blocks with TLLI. After receiving

the first RLC data block, network

will respond with PACKET

UPLINK ACK, in which “TLLI

received” should be set. If the TLLI

in the PACKET UPLINK ACK is

consistent with the one of MS, the

wireless resource for this message

is assigned to the MS. Otherwise,

MS should ignore the message.




Two-phase Access on CCCH

Contention Solution

After receiving the

second PACKET

UPLINK ASSIGN, MS

will compare the TLLI

contained in the message

with the one sent by

itself in PACKET

RESOURCE REQ. If the

two TLLIs are

consistent, the

contention solution is

successful.




Uplink TBF Establishment in PTM

MS Network

Packet Downlink Assignment

RLC/MAC BLOCK




Paging Flows

MS Network

Packet Channel Request

Packet Immediate Assignment

Packet Paging Response (LLC frame)

PRACH or RACH

PAGCH or AGCH

PACCH

PPCH or PCH Packet Paging Request




Uplink Data Transmission

Packet Uplink Ack/Nack

Data Block (CV=0)

Access and Assignment

MS BSS

PACCH

PDTCH

Packet Uplink Ack/Nack PACCH

PACCH

Data Block PDTCH

Data Block PDTCH

Data Block (last in send window)PDTCH

Data Block PDTCH

Data Block PDTCH

Data Block

final Packet Ack/Nack(FAI=1)PACCH

LLC PDU

SGSN

Packet Control Ack




Downlink Data Transmission

Packet Downlink Ack/Nack

MS Network

PACCH

Packet Downlink Assignment PACCH

PDTCH

PACCH final Packet Ack/Nack

Data Block PDTCH

Data Block PDTCH

Data Block (polling) PDTCH

PDTCH Data Block

PDTCH Data Block

Data Block

Data Block (last, polling) PACCH

Immediate Assignment AGCH

Packet Downlink Assignment

LLC PDU

SGSN

PACCH




Detach Signaling Flows

Upper left: Detach initiated by MSUpper right: Detach initiated by SGSN

Lower left: Detach initiated by MSC




Signaling Flow of Subscriber Authentication

1. SendAuthenticationInfo

1. SendAuthenticationInfo

2. AuthenticationandCipheringRequest

2. AuthenticationandCipheringResponse

MSBSS HLRSGSN

If SGSN did not sa

ve the authenticatio

n triple, it will send

HLR the “Send Authentication Info” m

essage, which conta

ins IMSI.

HLR responds with “

Send Authentication I

nfo Ack” that contains

authentication triple.Each authentication tr

iple contains RAND,

SRES and Kc.

SGSN sends MS

Authentication Re

quest (including R

AND, CKSN, and

encryption algorit

hm)

MS sends back Authentication Res

ponse (SRES) to f

inish authenticatio

n process




RAU intra SGSN

1. Routing Area Update Request

3. Routing Area Update Accept

2. Security Functions

MS BSS SGSN

4. Routing Area Update Complete




Cell Update (RAU intra RA)

BSC SGSN

1.1.

RA1

1. Send LLC PDU

Move from one

cell to anothercell within the

same RAC




PDP Deactivation Signaling FlowG

4. DeactivatePDPContext Accept

3. DeletePDPContext Resp

3. DeletePDPContext Requt

1. DeactivatePDPContext Request

SGSNMS

2. SecurityFunctions

1. DeletePDPContext

SGSN

1. DeletePDPContext

2. DeactivatePDPContext Accept

2. DeactivatePDPContext Request

MS

Initiated by Ms

Initiated by SGSN



Contents

A Brief Introduction to (E)GPRS Signaling Main (E)GPRS Signaling Flows

(E)GPRS Field Test




(E)GPRS Field Test

Test Purpose To understand customers’ true feeling

To collect information unobtainable inOMCR, including:

service model specific to each region;

radio environment specific to each region;

service performance in moving state.

Major technical support in specific areas(e.g. large gathering, sports events)

To handle customers’ complaints



(E)GPRS Field Test

Test ItemsCategories Test Items Relevant NEs

CQT

ATTACH SGSN

PDP GSN

WAP login WAP gateway

WAP refresh WAP gateway

WAP picture & ringtonedownload WAP gateway

PING INTERNET gateway

FTP download INTERNET gateway

Email upload/download INTERNET gateway

KJAVA download WAP gateway

DT

WAP login WAP gateway

WAP refresh WAP gatewayWAP picture & ringtone

downloadWAP gateway

FTP download INTERNET gateway

EGPRS coverage rate CELL

GPRS coverage rate CELL



(E)GPRS Field Test

Points for Attention before Test Test time: As PS service is influenced a lot by the number of users,

different test should be conducted at different time.

Cell reselection: As a result of the inherent defects in GSM system,cell reselection will inevitably lead to TBF interruption; in CQT,there should be no more than 4 cell reselections according toCMCC test protocol, otherwise, the tests for this cell will be invalid.

Traveling speed for the test: CMCC requires that DT should notexceed 40km/h in urban districts, and should not exceed 70km/hon expressway. In network optimization, the same traveling speedshould be adopted in the comparative tests before and after theoptimization.

Test level: PS service needs high C/I value, taking MCS9 as an

example, to reach an ideal rate, C/I should be above 20, and thelevel should be above -70dBm.



(E)GPRS Field Test

Points for Attention about Test Equipment Except test software, all software that may occupy

bandwidth in the test PC should be disabled;

Change the connection rate of testing handset to

115200 and disable the MMS Auto Extract

function; choose version R97 for GPRS test, and

versions above R97 for EGPRS test;

Points for attention about Modem setting:



(E)GPRS Field Test

Points for Attention about Test Equipment Setting of network connection;



(E)GPRS Field Test

Points for Attention in TestLevel: The mean RxLev in CQT should be above -70dBm, the mea

n RxLev in DT should be above -80dBm, and should not be lower t

han -90dBm.

Maximum TxPower: In PS service, MS does not perform power co

ntrol; during the test process, the maximum TxPower should be 33for GSM network and 30 for GSM1800 network.

BEP value: BEP value is specific to EGPRS. These two values are u

sed to decide which coding rate should be adopted, the maximum v

alue for CV_BEP and MEAN_BEP is 7/31 respectively, the average

value should be above 6.5/27.

Whether to enable frequency-hopping: It is not recommended to en

able frequency-hopping in PS service, and it is recommended to ad

opt BCCH frequency in RF frequency-hopping cells.



(E)GPRS Field Test

Points for Attention in TestNumber of channels & coding scheme: In a test, uplink should occ

upy a certain number of channels, e.g. CMCC protocol requires t

hat downlink should occupy 4 channels, and uplink should occupy

1 channel; the higher level the encoding mode, the better, and MC

S9 encoding mode should be over 90% during EGPRS test.

Block error rate: Occasional block error occurring under high-level

encoding mode is normal, but if there are continuous block errors,

it needs to pay attention to wireless quality and hardware.

Throughput: PS service test involves mainly RLC layer throughput

and APP throughput. RLC layer throughput is the actual throughp

ut on the Um interface, while APP throughput is the user data thro

ughput.



(E)GPRS Field Test

Points for Attention in Test

C1/C2: At present, PS servic

e shares the same C1/C2 al

gorithm as CS service. A co

mparison between C2 and R

xLev can display those cellswith unreasonable reselectio

n parameters. Conflicts betw

een CS service and PS servi

ce should be avoided during

the adjustment to unreasona

ble parameters.

CRH: In PS service,

CRH in GMM STAND

BY state works only

when an MS is crossing routing area and l

ocation area; while C

RH in GMM READY

state works all the ti

me.

CRO: This parameter

affects both CS servi

ce and PS service gr

eatly. As adjustment t

o this parameter tends to cause changes t

o cell load and hence

generate side effect, t

he adjustment should

be avoided as much

as possible.

PT & PO: These two

parameters can avoid

too fast the GPRS re

selection, but the ste

p size is too large, e.g. the step size is 10

dBm for PT, and 20s

for TO, which should

be paid close attentio

n to during adjustmen

t.



Contents

A Brief Introduction to (E)GPRS Signaling Main (E)GPRS Signaling Flows

(E)GPRS Field Test




(E)GPRS Field Test

Attach &Detach



(E)GPRS Field Test

PDP active & deactive



(E)GPRS Field Test

RAU



(E)GPRS Field Test

FTP & Ping

GO_NA28_E1_1 (E)GPRS Signaling Flow & Test

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