Call Set up Signaling In GSM

Traffic&Redesign LCC Pakistan GSM Protocol Architecture for Signaling 4... LCC Pakistan Traffic&Redesign Level 1-PCM transmission E1 or T1 Speech encoded at 16kbit/s and sub multiplex

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• GSM Interface & Layer’s Function

• Call setup Overview

• Key points in Call Setup.

• Explanation of each point with

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GSM Protocol Architecture for Signaling

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GSM Signaling Network Continue…

International Signaling relation via ISDN

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SS7 Signaling Architecture

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SS7 Layer in GSM Network

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SS7 Layers in GSM Network

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SS7 Layers in GSM Network…

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 Mobile-specific extension of C7 standard

 All messages exchanged between NSS Elements (MSC,HLR,VLR)

 A connectionless transport service provided by the SCCP

 Provides core functionality to support roaming

 Allows its users to access other users via worldwide C7/SS7 network

 Logical signalling connection between MSC and MS to support Layer 3 (MM/CM) message transfers

 Uses reduced set of C7 signalling instructions

 Routes messages via STPs

 C7 protocols responsible for routing and transport of signalling

messages

SS7 Layers in GSM Network…

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SS7 Layers in GSM Network…

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GSM Protocol Summery

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GSM Interfaces & Layers

Other Interfaces

E Interface

B,C Interface

A Interface

Abis Interface

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A Interface

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BSSMAP - deals with procedures that take place logically between the

BSS and MSC, examples : Trunk Maintenance, Ciphering, Handover, Voice/Data Trunk Assignment

DTAP - deals with procedures that take place logically between the MS

and MSC The BSS does not interpret the DTAP information, it simply repackages it and sends it to the MS over the Um Interface examples:

Location Update, MS originated and terminated Calls, Short Message Service, User Supplementary Service registration, activation,

deactivation and erasure

A Interface…

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A Interface…

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A Interface

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Abis Interface

may be 300, 1200, … is adjusted to 16 kbit/s

Abis Interface…

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Level 1-PCM transmission (E1 or T1)

Speech encoded at 16kbit/s and sub multiplexed in 64kbit/s time slots

Data which rate is adapted and synchronized

Level 2-LAPD protocol

Radio Signaling Link (RSL) Operation and Maintenance Link (OML)

Level 3-Application Protocol

Radio Subsystem Management (RSM) Operation and Maintenance procedure (OAM)

Abis Interface…

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Abis Interface…

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LAPD Message

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 The length is limited to 260 octets of information

 LAPD has the address of the destination terminal, to

identify the TRX, since this is a point to multipoint

interface

 Each TRX in a BTS corresponds to one or several

signaling links These links are distinguished by TEI

(Terminal Equipment Identities)

 SAPI=0, SAPI=3, SAPI=62 for OAM

LAPD Message…

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Um Interface

 Level 1-Physical

 Level 2-LAPDm(modified from LAPD)

constraints

 Level 3-Radio Interface Layer (RIL3) involves three sub layers

Message Services(SMS),

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Layer1 Signaling

Layer 2 Signaling

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• In LAPDm the use of flags is avoided

• LAPDm maximum length is 21 octets of information It makes use of

“more” bit to distinguish last frame of a message

• No frame check sequence for LAPDm, it uses the error detecting

performance of the transmission coding scheme offered by the physical

layer

LAPDm Message

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SMS) can exist simultaneously

SAPI(service access point identifier)

management on the Abis interface

different mobile stations, which is done by distinguishing the different

radio channels

LAPDm Message…

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Layer 3 Signaling

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Layer3 Signaling Message Format at air Interface

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Protocol Discriminator

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Transaction Identifier

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Message Type

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Information Element

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Measurement Report

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Layer 3 Function

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RR Management

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Mobility Management

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Connection Management

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RR Massage, Channel & MT Code

MM Massage

CM Message

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Call Setup Overview

• MS Idle Mode Behavior

• Call setup signaling flow with Layer2&Layer3 explanation

• Handover signaling flow

• Location updated signaling Flow

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MS Idle Mode Behavior

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Idle Mode Measurements explain in call Setup

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Call Setup Signaling Flow

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Call Setup Signaling Flow …

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Call Setup With Counters

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 Paging locates MS to cell Level for call

routing

 Three paging message types:

 Type 1 - 2 MSs using IMSI/TMSI

 Type 2 - 3 MSs (1xIMSI, 2xTMSI)

 Type 3 - 4 MSs using TMSI only

 Paging message requires 4 bursts (1

CCCH block)

 Paging messages may be stored at BSS

 Transmitted on PCH

 If DRX is implemented MS listens only

to allocated paging group

Paging Types

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Timers involved in Call Process

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Layer2&3 involved in Call setup

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Layer3 Message… RR Management Message

• To provide either the IMSI, the (P) TMSI but not the IMEI bases paging

IMSI <= 15 digts (P) TMSI= 4 Octets

• Odd/even indication Value 0 : Even number of identity digits (

Page Mode 00 Normal Paging

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Paging Request Type2

61

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Paging Request Type3

62

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System Information

in Idle Mode

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System Information Type1

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System Information Type1

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System Information Type2

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System Information Type2

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System Information Type 2ter

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System Information Type 2ter

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System Information Type3

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System Information Type3

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System Information Type3

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System Information Type4

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System Information Type4

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System Information Type4

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System Information

in Dedicated Mode

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System Information Type5

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System Information Type5

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System Information Type6

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System Information Type 6

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RR…Channel Request

Channel Request Message Format

Random Reference

• MS Generate Random Number (3 5bit) by

Using Random algorithm

• Number slot spread Tran

• Training Sequence Code(0 7)

After a suitable channel has been found, the BSC determines the most suitable training sequence code by examining all the interfering connections(C/I based)

• RF Hopping Channel(Hopping List)

Establishment cause is a 3 bit

• Answer to page

• MOC/MTC

• Location update

• SMS NECI(New establishment cause Indication) is disabled

• Timing Advance is

a access delay

(1 TA=550M)

• MA List

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Mobile Station Class mark

• Define certain attributes of the

MS equipment in use on a certain

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Cipher Response

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call setup

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Call Processing or Call Progress

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Assignment Command

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Assignment Command

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Assignment Command

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Assignment Command…

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Measurement Report Message format

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If the list of the Neighboring cells is changed by the operator ,this parameters (set=0,1) toggles it tells the locating algorithm in the BSC which neighboring cells description the MS has used , that is updated or old one

This bit indicate if the MS used Discontinuous Transmission on the

uplink

If 1 Dtx used, 0 is not used

These Element contains the averaged received signal level of the serving cells on all time slots and on subset of time slots The signal strength mapped on RX Level value between

0 63

RX Level 0= less than -110dbm

RX Level 1=-110dbm to -109dbm

RX Level 63=greater than -48dbm

The MS must send

continuous

measurement reports

but for some reason if

MS does not have

measurement , it can

indicate to the

network with this bit

These Element contains

the averaged received

signal Quality of the

serving cells on all time

slots and on subset of

time slots The signal

Measurements Report (MS Report after each 480ms)

These elements contains the averaged received signal strength, BCCH,

& Basic of the nth(n=1

to 6) Neighbor cells

• BCCH Allocation List….set to 1 in neighbor cells parameters description

• with 5 bits (0 31)

• BSIC consist of 6 bits

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HO Procedure

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Location Updated