GSM Protocol Suite - Lecture 4 - Mobile Computing, Lecture notes of Mobile Computing

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Presentation of the A-ter interface

BSC

TRAU

MSC

OMC

OAM

Transcoding

LAPD TS

Speech TS CCS7 TS X.25 TS Speech TS CCS7 TS X.25 TS PCM LINK

PCM

LINK

Presentation of the A-ter interface

Presentation of the A interface

Signaling Protocol Model

Inter MSC presentation

Radio PCM

O

A

M

R R L A P D L A P Dm

BTS

PCM PCM

MTP

SCCP

MTP

L

A

P

D

O

A

M

R

R

D T A P B S S M A P

BSSAP

BSC

PCMT1E1 MTP

MTP

MTP

SCCP

MTP

MTP

SCCP

I S U P / T U P

BSSAP

DTAP/

BSSMAP

T

C

A

P

MM

CM M

A

P

NSS

Radio L A P Dm

R

R

MM

CM

MS

Um Interface A bis Interface

A

Interface GSM protocol layers for signaling

GSM protocols - Message layer

• (^) Radio Resource (RR) sublayer
  • (^) basically implemented in the BSS
  • (^) manage the establishment, maintenance and release of radio connection between specific MS and the BSS despite user movement
  • (^) A radio connection include: » (^) a dedicated channel (SDCCH or TCH) allocation for connection » (^) SACCH » (^) a layer 2 radio link connection for signaling » (^) a circuit connection between BTS and BSC » (^) a circuit connection between BSC and MSC » (^) a SCCP connection between BSC and MSC

RR Protocol

Protocol discriminator Skip indicator Message type Information elements Protocol discriminator 0110 identifies the RR Management protocol. Skip identifier Value of 0000. Octet 1 2 3-n

00001 - - - Channel release messages: 101 CHANNEL RELEASE 010 PARTIAL RELEASE 111 PARTIAL RELEASE COMPLETE 00100 - - - Paging messages: 001 PAGING REQUEST TYPE 1 010 PAGING REQUEST TYPE 2 100 PAGING REQUEST TYPE 3 111 PAGING RESPONSE 00011 - - - System information messages: 000 SYSTEM INFORMATION TYPE 0 001 SYSTEM INFORMATION TYPE 1 010 SYSTEM INFORMATION TYPE 2 011 SYSTEM INFORMATION TYPE 3 100 SYSTEM INFORMATION TYPE 4 101 SYSTEM INFORMATION TYPE 5 110 SYSTEM INFORMATION TYPE 6 111 SYSTEM INFORMATION TYPE 7

RR Protocol

00000 - - - System information messages: 010 SYSTEM INFORMATION TYPE 2bis 011 SYSTEM IN FORMATION TYPE 2ter 101 SYSTEM INFORMATION TYPE 5bis 110 SYSTEM INFORMATION TYPE 5ter 00010 - - - Miscellaneous messages: 000 CHANNEL MODE MODIFY 010 RR STATUS 111 CHANNEL MODE MODIFY ACKNOWLEDGE 100 FREQUENCY REDEFINITION 101 MEASUREMENT REPORT 110 CLASSMARK CHANGE 011 CLASSMARK ENQUIRY

The main function of the Mobility Management (MM)

sub-layer is to support the mobility of user terminals,

such as informing the network of its present location and

providing user identity confidentiality.

The Mobility Management (MM) layer is in charge of

maintaining the location data, in addition to the

authentication and ciphering procedures.

A further function of the MM sub-layer is to provide

connection management services to the different entities

of the upper Connection Management (CM) sub-layer

MM Protocol

GSM protocols - Message layer

• (^) Mobility Management (MM) sublayer
  • (^) MM common procedure:
    • (^) can be initiated during an MM-specific procedure or while an MM connection is in place
    • (^) Procedures are: » (^) IMSI detach » (^) TMSI allocation » (^) Authentication, Identification

MM Protocol

Protocol discriminator Skip indicator Message type Information elements Protocol discriminator 0101 identifies the MM protocol. Skip identifier Value of 0000. Octet 1 2 3-n

Message type MM message types may be as follows. Bit 8 is reserved for possible future use as an extension bit. Bit 7 is reserved for the send sequence number in messages sent from the mobile station. 0x00- - - - Registration messages: 0001 IMSI DETACH INDICATION 0010 LOCATION UPDATING ACCEPT 0100 LOCATION UPDATING REJECT 1000 LOCATION UPDATING REQUEST 0x01- - - -Security messages: 0001 AUTHENTICATION REJECT 0010 AUTHENTICATION REQUEST 0100 AUTHENTICATION RESPONSE 1000 IDENTITY REQUEST 1001 IDENTITY RESPONSE 1010 TMSI REALLOCATION COMMAND 1011 TMSI REALLOCATION COMPLETE 0x10- - - -Connection management messages: 0001 CM SERVICE ACCEPT 0010 CM SERVICE REJECT 0011 CM SERVICE ABORT 0100 CM SERVICE REQUEST 1000 CM REESTABLISHMENT REQUEST 1001 ABORT 0x11- - - -Miscellaneous messages: 0001 MM STATUS

MM Protocol

GSM protocols - Message layer

• (^) Connection Management (CM) sublayer
  • (^) take place between MS and MSC
  • (^) Functions are:
    • (^) Call control » (^) establishment of communications between users » (^) release of communications » (^) transfer of dialed number and dialing tones » (^) switch from speech mode to data mode