Bài Giảng GSM Protocols

OSI Reference Model Layer were independent each other..  Physical layer: Modulation, What kind of channel, Decide the interface..  Data link layer: Convert packets into frames,Error d

GSM Protocols

GSM Architecture

Interfaces

Purpose of layering

 Divides the complexity of internetworking into discrete steps

 Protocol: Set of rules that end points in a

telecommunication connection use when they communicate

OSI Model

OSI Reference Model

 Layer were independent each other

 Physical layer: Modulation, What kind of channel, Decide the interface

 Data link layer: Convert packets into

frames,Error detection and correction

 Network Layer: Every network node has to analyse

 Transport Layer: Segmentation end to end ordering packets

 Session Layer: Global synchronization Purpose.

 To differentiate mobile terminating call,

mobile,orginating call,location update

GSM Protocol Stack

Physical layer

ISDN Channels

LAPDm

 maximum frame length of an LAPDm frame (=

23 byte or 184 bit)

 Information frame: 1st byte, bit 0 = 0

 Supervisory frames: 1st byte, bit 0 = 1, bit 1 = 0

 Unnumbered frames: 1st byte, bit 0 = 1, bit 1

= 1

Control Field

Send Sequence Number and Receive Sequence Number

Polling Bit (P-Bit), Final Bit (F-bit), and Bit

P/F- Polling Bit frame types that can be used only

as commands

 Final Bit frame types that can be used only as

Responses

 P/F-Bit frame types that can be used both

command and Response

 To transport the actual signaling data

 Every DCCH and every ACCH use this format

 The maximum length of the Layer 3

information to be carried is restricted,

depending on the channel type (FACCH,

SACCH)

B-format

 The number of unacknowledged frames for the service access point identifier (SAPI) = 0 is

two, and the number of unacknowledged

frames for SAPI = 62 and for SAPI = 63 is one

C/R

 For transmission of BCCH, PCH, and AGCH

 There is no header in the Bbis-format that

would allow for addressing or frame

LAPD

Terminal Endpoint

Identifier

 distinguish among the various

TRXs One TEI is assigned to each TRX

 That provides the ability to

distinguish between TRXs during analysis of a trace file.

Layer3(RR,MM,CM)

MM

CM

CM