Call setup-procedure

Traffic&Redesign LCC Pakistan

Traffic&Redesign

• Call setup,Mobility&Integrity is a Key of Optimization

Objective

LCC Pakistan2

Traffic&Redesign

• GSM Protocol Architecture for Signaling

• International Signaling relation via ISDN

• GSM Interface & Layer’s Function

• Call setup Overview

• Key points in Call Setup.

• Explanation of each point with layer 3&2

message & logical channels.

• Question &Answers

Outline

LCC Pakistan3

GSM Protocol Architecture for Signaling

GSM Signaling Network Continue…

Traffic&Redesign LCC Pakistan5

International Signaling relation via ISDN

LCC PakistanTraffic&Redesign

SS7 Signaling Architecture

SS7 Layer in GSM Network

SS7 Layers in GSM Network

SS7 Layers in GSM Network…

Mobile Application Part (MAP) Mobile-specific extension of C7 standard. All messages exchanged between NSS Elements

(MSC,HLR,VLR) Transaction Capabilities Application Part (TCAP)

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 Signalling Connection Control Part (SCCP)

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

Message Transfer Part (MTP) C7 protocols responsible for routing and transport of

signalling messages

SS7 Layers in GSM Network…

GSM Protocol Summery

GSM Interfaces & Layers

A Interface

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…

A Interface

Abis Interface

Messages exchanges between the BTS and BSC. Traffic exchanges Signaling exchanges

Physical access between BTS and BSC is PCM digital links of E1(32) or T1(24) TS at 64kbit/s.

Speech: Conveyed in timeslots at 4X16 kbit/s

Data: Conveyed in timeslots of 4X16 kbit/s. The initial user

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

Abis Interface…

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 protocolRadio Signaling Link (RSL)Operation and Maintenance Link (OML).

Level 3-Application ProtocolRadio Subsystem Management (RSM)Operation and Maintenance procedure (OAM)

Abis Interface…

LAPD Message

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…..

Um Interface

Level 1-Physical TDMA frame Logical channels multiplexing

Level 2-LAPDm(modified from LAPD) No flag No error retransmission mechanism due to real

time constraints Level 3-Radio Interface Layer (RIL3) involves three

sub layers RR: paging, power control, ciphering execution,

handover MM: security, location IMSI attach/detach CM: Call Control(CC), Supplementary Services(SS),

Short Message Services(SMS),

Layer1 Signaling

Layer 2 Signaling

• 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

The acknowledgement for the next expected frame in the indicator N(R ).

On radio interface two independent flows(one for signaling, and one for SMS) can exist simultaneously.

These two flows are distinguished by a link identifier called the SAPI(service access point identifier).

LAPDm SAPI=0 for signaling and SAPI=3 for SMS. SAP1=0 for radio signaling, SAPI=62 for OAM and SAPI=63 for

layer 2 management on the Abis interface. There is no need of a TEI, because there is no need to

distinguish the different mobile stations, which is done by distinguishing the different radio channels.

LAPDm Message….

Layer 3 Signaling

Layer3 Signaling Message Format at air Interface

Protocol Discriminator

Transaction Identifier

Message Type

LCC PakistanTraffic&Redesign 35

Information Element

Measurement Report

Layer 3 Function

RR Management

Mobility Management

Connection Management

RR Massage, Channel & MT Code

MM Massage

CM Message

Call Setup Overview

• MS Idle Mode Behavior• Call setup signaling flow with Layer2&Layer3 explanation • Handover signaling flow• Location updated signaling Flow

MS Idle Mode Behavior

Idle Mode Measurements..explain in call Setup

Call Setup Signaling Flow

Call Setup Signaling Flow …

Call Setup With Counters

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

Timers involved in Call Process

Layer2&3 involved in Call setup

Call Setup Measurements

Layer3• RR Management Message• MM Management Message• CM Management Message

Layer2• RR-RSP• I-CMD• SABM-CMD• UA-RSP• DISC-CMD• Call Setup• Call Establishment• Call End

Layer3 Message…. RR Management Message

RR …Paging Message Structure

Protocol Discriminator

The Channel Field (bits 1-2 of octet 2) indicates the further combination of channel which will be needed. It is coded as follows

RR-Paging Message

Paging Request Type1

Mobile Identity• 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 (

• Type of Identity

Page mode• To control the action of MS belonging to the paging subgroup corresponding to the pagingsubchannel.

Page Mode 00 Normal Paging 01 Extended Paging 10 Paging Re

organisation 11 Same as before

Channel Needed• To indicate what type of channel is required for the transaction linked to the paging procedure. First Channel 00 Any channel 01 SDCCH 10 TCH/F 11 TCH/H or TCH/F Second Channel Same as first channel

RR… System Information

1. PD for System Information is always 6.2. Skip Indicator is 00003. Message Type as below Protocol Discriminator

System Information in Idle Mode

System Information Type1

System Information Type 2ter

System Information in Dedicated Mode

System Information Type 6

RR…Channel Request

Channel Request Message Format Random Reference

• MS Generate Random Number (3...5bit) by Using Random algorithm.• Number slot spread Tran• No of Max Retransmission

Establishment cause (3 bit).• Answer to page• MOC/MTC• Location update• SMS NECI Parameters setting is explain in next slide

Disable NECI

Enable NECI

Channel Request Message….

Immediate Assignment

Channel Control Parameters• Separated/Combined/HybridChannel configuration. • 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 causeIndication) is disabled.

• Timing Advance is a access delay.(1 TA=550M)• MA List

CM Service RequestCM Service Type

To specify which service is requested from network

Mobile Station Class mark

• Define certain attributes of the MS equipment in use on a certain transaction.

Mobile Identity•

Mobile Station Class mark

• Define certain attributes of the MS equipment in use on a

certain transaction. • Revision Level

• Establish Indication • Encryption Algorithm• RF Power Capability

• SOLSA (Support of localized service area) • VBS/VGCS

• CM Service Prompt• SM Capability

Cipher Response

call setup

Call Processing or Call Progress

Assignment Command

Assignment Command…

Measurement Report Message format

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 quality

mapped to a corresponding BER

% value before decoding as follows.

RX Qual 0= BER<0.2%

RX Qual1=BER 0.2% to 0.4% .

.RX Qual

7=BER>12.8%.

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

HO Procedure

Location Updated

Open Discussion…

Question&Answer

Call setup-procedure

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