abis messages

NTC CTXX 0677 Issue 4.0 en

Nokia Telecommunications Oy

1 (119)

GSM 900/1800 BSS

Signalling Examples Training Document

Signalling Examples

2 (119) Nokia Telecommunications Oy

NTC CTXX 0677Issue 4.0 en

The information in this document is subject to change without notice and describes only the product defined in the introduction of this documentation. This document is intended for the use of Nokia Telecommunications' customers only for the purposes of the agreement under which the document is submitted, and no part of it may be reproduced or transmitted in any form or means without the prior written permission of Nokia Telecommunications. The document has been prepared to be used by professional and properly trained personnel, and the customer assumes full responsibility when using it. Nokia Telecommunications welcomes customer comments as part of the process of continuous development and improvement of the documentation.

The information or statements given in this document concerning the suitability, capacity, or performance of the mentioned hardware or software products cannot be considered binding but shall be defined in the agreement made between Nokia Telecommunications and the customer. However, Nokia Telecommunications has made all reasonable efforts to ensure that the instructions contained in the document are adequate and free of material errors and omissions. Nokia Telecommunications will, if necessary, explain issues which may not be covered by the document.

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Copyright Nokia Telecommunications Oy 1999. All rights reserved.

Contents



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Contents

1 Signalling procedures............................................................................4 1.1 Radio access part.....................................................................................4 1.2 Establishment part ...................................................................................5 1.3 Location update or call setup ...................................................................5 1.4 Conversation part .....................................................................................6 1.5 Release after call or location update ........................................................6

2 Mobile call signalling .............................................................................7 2.1 Mobile Originated Call Signalling Example ..............................................8 2.2 Mobile Terminated Call Signalling Example...........................................41

3 Location update....................................................................................72 3.1 Normal location update ..........................................................................72 3.2 Periodic location update.........................................................................72 3.3 IMSI attach/detach location update ........................................................72 3.4 Location Update Signalling Example......................................................74

4 Handovers.............................................................................................92 4.1 Inter-Cell Handovers ..............................................................................92 4.2 Intra Cell Handovers...............................................................................94 4.3 Handover Signalling Examples ..............................................................95

5 BCCH and system information .........................................................113 5.1 System info type -messages ................................................................113 5.2 Information elements............................................................................116

Signalling Examples



1 Signalling procedures The BSS signalling procedures are mainly related to actions and events triggered by or for the MS. This document describes the signalling procedures, the signalling flow and the messages used for the various services.

In this part the different phases of the signalling procedures are explained.

1.1 Radio access part

Before any signalling event (e.g. MOC or LUP) can take place the MS has to make a radio access. This consists of three phases, the random access, the channel activation and the immediate assignment.

The MS will send a RACH burst to the BTS when performing a location update, originating a call, or answering a page in the case of an MTC. When a RACH is received, the BTS requests a signalling channel from the BSC. The BSC will activate an SDCCH in the BTS. The BSC then sends an Immediate Assignment message (AGCH on Air interface) which will tell the mobile to use the assigned SDCCH channel.

During radio access the communication is based on a Random Reference Number produced by the MS. The MS will send a random number with the RACH burst and the BSC will include this number in the Immediate Assignment Command. The other RACH related parameters are described in the BCCH description in this document.

Signalling procedures



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1.2 Establishment part

After the MS has started transmitting on the SDCCH it will send a signalling connection establishment message, SABM. This message has to be acknowledged by the BTS with a UA-message. Included in the SABM message is the first MM-message describing the service required by the MS. Once the signalling connection between the MS and the BTS has been established, and the MS has requested a service, the SCCP connection-oriented signalling can begin on the A interface.

1.3 Location update or call setup

After the signalling connections have been established the procedure varies depending on the type of service requested.

Location Update In the case of a Location Update Request, the MSC will check the MS identity based on IMSI or TMSI and perform authentication. If this is successful, ciphering is activated, after which the MS equipment identity can be checked. With the Location Update Accepted message the MSC will allow the MS to access the network and a new TMSI is allocated.

Call Setup After the authentication, ciphering and TMSI reallocation procedures as described above have been completed, the system has to assign a traffic channel (TCH) to the MS. All of these procedures may vary, depending on the network settings.

The setup of the call is divided into two parts, traffic channel assignment and connection of the call. The traffic channel is taken into use during the assignment procedure. The procedure starts with an Assignment Request and can be split into three phases. The first phase consists of A-interface TCH allocation and of Air interface TCH activation. The MSC will inform the BSC which speech circuit will be used on the A-I/F and the BSC will activate a TCH in the BTS for the MS.

The second phase is to assign the channel to the MS. When the MS switches to the assigned TCH it will use FACCH mode (stealing mode) to send signalling. The third phase is to start the signalling connection with SABM. After this, the MS will use the assigned signalling connection, FACCH, to send an Assignment Complete message to the MSC.

Signalling Examples



Once the channels have been successfully allocated between the subscribers, the second part of call setup takes place. This involves alerting the called party (the phone rings) and connection (if the phone is answered).

1.4 Conversation part

The conversation part can start when the Connect Acknowledgement message is received. During the conversation there will be measurement signalling between the MS, BTS and BSC. If required the BTS can change the Timing Advance of the MS and the BSC can make decisions on power level modifications or handovers. It is also possible to send SMS messages on the SACCH.

1.5 Release after call or location update

When either the called or the calling party hangs up, the Disconnect message will be sent. This initiates the release procedure, which can be divided into four phases. Firstly, the call connection will be released and then the signalling connections (FACCH and the associated SACCH) can be disconnected. When the logical resources using the physical TCH have been cleared the RF channel can be released. Last part of the release is to clear the SCCP connection-oriented signalling communication between MSC and BSC.

In the case of a Location Update the used resources will be cleared in the same way. This will happen after the Location Update Accepted message is received by the MS and the TMSI reallocation is completed. The RF resource used in this case is an SDCCH with its associated SACCH.

Mobile call signalling



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2 Mobile call signalling This section describes the signalling message flow of a mobile call. The signalling message flow of a mobile originated call differs from that of a mobile terminated call. The signalling flow will also be affected when the release of the call is made by the calling or called party. The particular messages are explained in the signalling examples below.

Signalling Examples



2.1 Mobile Originated Call Signalling Example

M S C B S C B T S M S V LR C h ann e l R equ ired

C h ann e l A c tiva t ion

C h ann e l A c tiva t ion A c k .

Im m edia te A s s ig m ent C om m an d.

C h ann e l R equ es t ( R A C H )

Im m edia te A s s ig m ent ( A G C H ) . C M S erv ic e R equ es t ( S D C C H )

E s tab lis h In d ic a tionC R (C M S erv ic e R equ es t)P roc ess A c c es s R equ es t

A u th entic a te D T 1A uth en tic a tion R equ es t

A uth entic a tion R equ es t ( S D C C H )

A uth entic a tion R esp ons e ( S D C C H )D T 1 A uth en tic a tion R esp ons e

A u th entic a tion R es p ons e S et C ip h er in g M od e

D T 1 C iph ering M od e C om m an d

E nc ryp tion C om m an d C ip h er in g M od e C om m and ( S D C C H ) C ip h er in g M od e C om ple te ( S D C C H )

D T 1 C iph ering M od e C om p leteA c c es s R equ es t A c c epted

F orw ard N ew T M S I T M S I R ea lloc a tion C om m and

T M S I R ea lloc a tion C om m and ( S D C C H )

T M S I R ea lloc a tion C om ple te ( S D C C H )T M S I R ea lloc a tion C om p le te

T M S I A c k . S etup ( S D C C H )

D T 1 S etu pS en d In f o f or O .G . C a ll

C om ple te C a ll D T 1 C a ll P roc eed ing

C all P roc eed ing ( S D C C H )D T 1 A s s ig n m ent R eq u es t

P h ys ic al C on text R equ es t

P h ys ic al C on text C onf irm ed

C h ann e l A c tiva t ion

C h ann e l A c tiva t ion A c k .

A s s ign m ent C om m and ( S D C C H )

S A B M ( F A C C H )E s tab lis h In d ic a tion

U A ( F A C C H )

A s s ign m ent C om p le te ( F A C C H )D T 1 A s s ig n m en t C om p lete

R F C h an n e l R e leas e

R F C h an n e l R e leas e A c k .D T 1 A le rt in g

A ler tin g ( F A C C H )D T 1 C onn ec t

C on n ec t ( F A C C H )

C on n ec t A c k .( F A C C H )D T 1 C onn ec t A c k .

M eas urem en t R ep o rt ( S A C C H ) M eas urem en t R ep o rt/R es u lt

D is c onn ec t ( F A C C H )D T 1 ( D is con n ec t )

D T 1 ( R e leas e )

D T 1 ( R e leas e C om ple te)

D T 1 ( C lear C om m an d )

R eleas e ( F A C C H )

R eleas e C om p le te ( F A C C H )

C h ann e l R ele as e ( F A C C H )

D eac tiv a te S A C C HD IS C ( F A C C H )

U A ( F A C C H )R eleas e In d ic a tion

R F C h an n e l R e leas e

R F C h an n e l R e leas e A c k .D T 1 ( C lear C om p lete )

R LS D ( S C C P R e leas ed )

R LC ( S C C P R e leas ed A c k .)

1 2

34

56

7 89

1011 12 13

1415 16

17 18 19

20 21

22 2324 25 26

2728 29

30 31 32

33 34 35

3637 38

394 0

4142

43 44

4546 47

4 8495 0

5 15 2

5354 5556 57

58 59

60 6162 63

64 6566

67 6869

707172

73 74

U A (S D C C H )

R A D IO A C C E S S P A R T

E S T A B L IS HM EP A R T

C IP H E R ING , A U T H E N T IC A TA N D C AL L S E TP AR T

T C H S E IZ E D

C O N V E R S A T IP A R T

C M S erv ic e R equ es t

C ip h er in g M od e C om m and

S A B MC R (C M S erv ic e R equ es t)

C C

R E LE A S E B Y




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1. Channel Request (MS to BTS;RACH) The MS requests a channel by sending a random access burst on a RACH channel to a BTS. The Channel request message contains the establishment cause (3 bits) which can be response to paging, emergency call or 'other services' e.g. Mobile Originated Call, Short Message Service or Location Update. Additionally, this message contains a Random Reference, which consists of 5 bits randomly selected by the MS. This random reference is used to separate two MSs that are attempting to access the network at exactly the same time.

2. Channel Request (BTS to BSC;BTSM) Upon receiving the Channel Request message from the MS, the BTS sends a Channel-Required message to the BSC, which contains the information contained in the channel request. To this, the BTS adds the TDMA frame number and the Access Delay, which is the first timing advance estimate made by the BTS.

CHAN RQD (CCh) T=0

Channel Nr

- uplink CCCH (RACH)

- timeslot : 0

Req. Ref

- MOC, SMS

- random reference : 2 (2h)

- N32 : 11 (bh)

- N26 : 14 (eh)

- N51 : 35 (23h)

Access Delay

- value : 0 (00h)

Signalling Examples



3. Channel Activation(BSC to BTS;BTSM) After receiving the Channel-Required message, the BSC allocates an SDCCH -channel for this call. It sends a Channel Activation message to the BTS containing the following parameters: DTX control, channel description, mobile allocation, maximum power levels of the MS and BTS and the timing advance as calculated by the BSC.

CHAN. ACT. (DCh) T=0

Channel Nr

- SDCCH/8 subchannel 1

- timeslot : 1

Act. Type

- immediate assignment procedure

Channel Mode

- length : 4

- downlink DTX not used, uplink DTX not used

- channel type : 03h 01h 00h

Channel Id

- length : 6

- SDCCH/8 subch 1

- timeslot : 1

- training sequence code : 0

- hopping : 0

- Frequency band nr : 3

- ARFCN : 92 (5ch)

- frequencies included from CA :

BS Power

- power control level : 14 (eh)

MS Power

- power control level : 0 (0h)

Timing Adv.

- 0 (00h) (0 km)




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4. Channel Activation Ack (BTS to BSC;BTSM) A response to the Channel Activation message. When the BTS has received this message it starts to send and receive on the SACCH channel.

CHAN. ACT. ACK (DCh) T=0

Channel Nr


- timeslot : 1

Frame Number

- N32 : 11 (bh)

- N26 : 24 (18h)

- N51 : 45 (2dh)

5. Immediate Assignment Command (BSC to BTS;BTSM;L3)

The BSC tells the BTS about the characteristics of the SDCCH channel to use.

IMM.ASS. CMD (CCh) T=0

Channel Nr

- downlink CCCH (PCH + AGCH)

- timeslot : 0

Imm. Ass. Info

- value (hex) : 06 3F 00 49 03 5C E2

5C 6E 00 00

IMMEDIATE ASSIGNMENT (RR)

Page Mode

- normal paging

Channel Description


- timeslot : 1


- hopping : 0


- ARFCN : 92 (5ch)

Signalling Examples



Request Reference

- MOC, SMS


- N32 : 11 (bh)

- N26 : 14 (eh)

- N51 : 35 (23h)

Timing Advance

- 0 (00h) (0 km)

Mobile Allocation


6. Immediate Assignment (BSC to MS;AGCH) The BSC informs the MS via the BTS on the AGCH channel the characteristics of the SDCCH channel to be used. Parameters include the page mode, SDCCH channel description, SACCH, hopping indicator, the initial timing advance, and mobile allocation (if frequency hopping applies). Additionally, the request reference (random reference and the TDMA frame number) originally sent by the MS is included to identify the relevant MS. The MS is then able to switch to this SDCCH channel.

7. CM Service Request (MS to BTS;SDCCH) SABM (LAPDm) After receiving the IMMEDIATEASSIGNMENT message, the MS tunes to the assigned SDCCH and starts to establish the signalling link across the network. The MS sends the layer 2 SABM to the BTS on the SDCCH. The SABM contains a layer 3 service request message indicating the service type required to the network through the service request message.

8. CM Service Request (BTS to BSC; L3) Establish Indication (BTSM)

BTS acknowledges the Immediate Assignment Command by returning Establish Indication message. Establish indication -message has two uses. Firstly, when used in this phase it points out that from the BTS point of view, the MS is now on the SDCCH-channel. Also the BTS identifies the link id as the main signalling channel and adds received Layer 3 information into this message. The BSC starts the handover algorithm.

EST. IND (RLL) T=0

Channel Nr


- timeslot : 1

Link Id




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- main DCCH (FACCH or SDCCH)

- SAPI : 0

L3 Info

CM SERVICE REQUEST (MM)

CM Service Type

- value : 1h

Ciphering Key Seq. Nr

- value : 2h

MS Classmark 2

- length : 2 (02h)

- revision level : reserved for phase 1

- encryption algorithm A5

- class 1, vehicle and portable

- frequency band 0

- short message capability present

Mobile Identity

- length : 5h

- TMSI : ca290100

9. Complete L3 Information (BSC to MSC;BSSMAP) CM Service Request ( L3 )

The CM Service Request message is forwarded to the MSC

- BSSMAP (length : 22, 16h)

COMPLETE L3 INFORMATION

Cell Identifier

- length : 5 (05h)

- cell identified with LAC + CI

- location area code : 1369 (0559h)

- cell identifier : 174 (00AEh)

Layer 3 Information

-length : 12 (0Ch)

CM SERVICE REQUEST (MM)

Signalling Examples



CM Service Type

- value : 1h


- value : 2h

MS Classmark 2

- length : 2 (02h)




- frequency band 0


Mobile Identity

- length : 5h

- TMSI : ca290100 10. UA (BTS to MS;SDCCH LAPDm) The BTS acknowledges the SABM sent by the MS.

11. Process Access Request (MSC to VLR;CCS7 MSC forwards MS's request for access management from

VLR by Process Access Request message.

12. Authentication (VLR to MSC;CCS7) VLR initiates authentication request by sending an Authenticate

message to MSC.

13. Authentication Request (MSC to BSC ; L3)

The network sends this message to the mobile to initiate the authentication of the mobile station identity. The mobile uses the RAND as an input to the authentication algorithm to calculate the response, SRES.

- DTAP (length : 19, 13h)

- SAPI : 0, main DCCH is used

AUTHENTICATION REQ (MM)





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- value : 2h

Auth. Parameter RAND

741D0912FA6493F91D8AC833ACA2075D

14. Authentication Request (BSC to BTS ;BTSM L3)

(BTS to MS ; SDCCH L3)

DATA REQ (RLL) T=1

Channel Nr


- timeslot : 1

Link Id


- SAPI : 0

L3 Info



- value : 2h


741D0912FA6493F91D8AC833ACA2075D

This element is used to identify a previously calculated and stored ciphering key (Kc) in the mobile. The mobile stores this sequence number it received from the network with the corresponding Kc.

15. Authentication Response

(MS to BTS;SDCCH L3)

(BTS to BSC; BTSM L3) The MS responds to the Authentication Request with the Signed Response SRES. There are two algorithms used in the Authentication procedure, A3 and A8. In the MS, these algorithms are stored on the SIM card, along with a 32-digit key called Ki. The same information can be found in the Authentication Centre (AuC). When the network requests MS Authentication, the AuC/VLR sends a 32 digit RANDom Number to the MS. The MS calculates the Signed Response (SRES) and sends it to the VLR. The VLR then compares the MSs SRES with the AuCs SRES and if they are the same, the call set-up can continue.

Signalling Examples



Note The first 8 digits of the Ki are used for Authentication and SRES calculation, the other 24 are reserved for Ciphering Key (Kc) calculation.

DATA IND (RLL) T=1

Channel Nr


- timeslot : 1

Link Id


- SAPI : 0

L3 Info

AUTHENTICATION RSP (MM)

Auth. Parameter SRES : 741C0B11 16. Authentication Response (BSC to MSC; L3)

The BSC forwards the SRES to the VLR.




Auth. Parameter SRES : 741C0B11 17. Authentication Response (MSC to VLR) MSC sends a positive response to Authenticate message.

18. SET_CIPHERING_MODE VLR sends MSC Set Ciphering Mode message that is used for changing MS-BTS connection ciphering status.

19. Cipher Mode Command (MSC to BSC;BSSMAP) The MSC uses this command, which includes Kc to initiate ciphering if the function is enabled.


CIPHER MODE COMMAND




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L3 Header Information

- length : 2 (02h)

- protocol discr. : Radio Resources

- transaction id. : 0 (0h)

- message send from originating side

Encryption Information

- length : 9 (09h)

- GSM user data encr. v. 1

- ciphering key, length : 8 (08h)

FE 61 95 FE E5 73 32 C8

------------------------------------------------------------------------------------------------

Layer 3 Header Information

This element is used to supply the BSS with the necessary information in order to carry the layer 3 messages to the mobile over the radio interface.


length : d (xh)

protocol discriminator pd text

transaction identifier : d (xh)

message sent dir text originating side

Protocol discriminator

value pd text

3h Call Control

5h Mobility Management

6h Radio Resources

9h SMS with call

Bh SMS wthiout call

Fh GSM test procedures

others Unknown protocol discriminator : d (xh)

The dir text is replaced with "to", if the TI flag is set to one. Otherwise "from" is displayed.

Encryption information

This element carries the user data encryption information necessary to control the encryption equipment in the BSS.

Signalling Examples



------------------------------------------------------------------------------------------------

Encryption information

length : d (xh)

algorithm id text

ciphering key, length : d (xh)

xx xx xx xx xx xx xx xx

Algorithm idetifier

Phase 1:

Value algorithm id text

1 no encryption required

2 GSM encryption version 1

others Unknown algorithm id : d (xh)

Phase 2:

Bit No algorithm id text

1 no encryption required

2 GSM user data encryption version 1 (A%/1)

3 GSM A5/2

4 GSM A5/3

5 GSM A5/4

6 GSM A5/5

7 GSM A5/6

8 GSM A5/7

The chipering key bytes shall be displayed in hex in the order they apper in the information element

20. Ciphering Mode Command (BSC to BTS;L3) Establishment Command (BTSM)

The BSC stores the Encryption information and forwards the command to the BTS. If the BTS software contains the algorithm specified by the MSC it can start ciphering, otherwise it sends a reject message back to the MSC.

ENCR. CMD (DCh) T=0

Channel Nr


- timeslot : 1

Encr. Info




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- lentgh : 9

- GSM A5/1

- ciphering key : FE 61 95 FE E5 73

32 C8

Link Id


- SAPI : 0

L3 Info

CIPH. MODE COMMAND (RR)

Cipher Mode Setting

- start ciphering 21. Ciphering Mode Command (BTS to MS;SDCCH) The BTS commands the MS to start ciphering (whether required or not) and starts receiving in the ciphered mode.

22. Ciphering Mode Complete

(MS to BTS to BSC;SDCCH BTSM L3)

DATA IND (RLL) T=1

Channel Nr


- timeslot : 1

Link Id


- SAPI : 0

L3 Info

CIPH. MODE COMPLETE (RR) The MS acknowledges the ciphering command in the specified cipher mode. This message may include the IMEI.(for phase 2)

23. Cipher Mode Complete (BSC to MSC;BSSMAP)

The BSC forwards the cipher response to the MSC.


CIPHER MODE COMPLETE

Signalling Examples



24. Access Request Accept (MSC to VLR;CCS7) VLR sends a positive acknowledge to Process Access Request message.

25. Forward New TMSI (VLR to MSC;CCS7) VLR requests MSC to perform TMSI reallocation.

25+. Identity Request (MSC to BSC to BTS to MS)



IDENTITY REQUEST (MM)

Identity Type

25++. Identity Response(MS to BTS to BSC to MSC)

DATA IND (RLL) T=1

Channel Nr


- timeslot : 1

Link Id


- SAPI : 0

L3 Info

IDENTITY RESPONSE (MM)

Mobile Identity

- length : 8h

- IMEI : 495000100676140

26. TMSI Reallocation Command (MSC to BSC; L3)

The purpose of the TMSI reallocation procedure is to provide identity confidentiality. Usually the TMSI reallocation is performed at least at each change of location area. MSC initiates the TMSI reallocation procedure by sending TMSI Reallocation command message to the MS. TMSI Reallocation Command message contains a new combination of TMSI and LAI allocated by the network or a LAI and the IMSI if the used TMSI shall be deleted. Usually the TMSI Reallocation Command message is sent to the MS by using a RR connection in ciphered mode.

- DTAP (length : 13, 0Dh)




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TMSI REALLOC COMMAND (MM)

Location Area Id.

- MCC : 262

- MNC : 09

- LAC : 1369 (559h)

Mobile Identity

- length : 5h

- TMSI : ca2a0100 27. TMSI Reallocation Command

(BSC to BTS to MS;BTSM SDCCH L3)

DATA REQ (RLL) T=1

Channel Nr


- timeslot : 1

Link Id


- SAPI : 0

L3 Info


Location Area Id.

- MCC : 262

- MNC : 09

- LAC : 1369 (559h)

Mobile Identity

- length : 5h

- TMSI : ca2a0100 ---------------------------------------------------------------------------------------- Location Area Identification

The purpose of this element is to uniquely idetify a location area withn GSM network. This information is broadcast on the BCCH to all mobiles. Mobiles use this information to decide when there is a need to update the location information of that mobile to the network.

Signalling Examples



Location Area Id.

MCC : ddd

MNC : dd

LAC : d (xh)

------------------------------------------------------------------------------------------------

Mobile Identity

length : d (xh)

identity text : dddd

Type of identity

value identy text

0 no identity

1 IMSI

2 IMEI

3 IMEISV

4 TIMSI

other Unknown identity type : d (xh)

If the number of digits is even, the upper nibble of the last octet is then interpreted as spare bits. In IMSI, they must be set to one.

28. TMSI Reallocation Complete (MT to BTS to BSC;SDCCH BTSM L3)

DATA IND (RLL) T=1

Channel Nr


- timeslot : 1

Link Id


- SAPI : 0

L3 Info

TIMSI REALLOC COMP. (mm)

When the MS receives the TMSI Reallocation Command message, it stores the LAI in the SIM. If the received identity is the IMSI of the MS, it deletes any previously stored TMSI. If the received identity is a TMSI, the MS stores it in




23 (119)

the SIM. In both cases the MS send a TMSI Reallocation Complete message to the network.

29. TMSI Reallocation Complete (BSC to MSC ; L3)

TMSI Reallocation Complete message is forwarded to the MSC.



TMSI REALLOC COMPL. (MM)

30. TMSI Ack (MSC to VLR;CCS7) MSC sends VLR a positive response to reallocation of TMSI.

31. Setup (MS to BTS to BSC ;SDCCH BTSM L3) After authentication, Identification and Ciphering, the MS is on the SDCCH channel and ready to start real call setup signalling. The MS sends a Setup message to the BSC to be forwarded to the MSC

DATA IND (RLL) T=1

Channel Nr


- timeslot : 1

Link Id


- SAPI : 0

L3 Info

SETUP (CC)

Bearer Capability

- length : 1 (1h)

- info xfer cap : speech

- xfer mode : circuit

- coding std : GSM standardized

- radio ch req: full rate ch required

Called Party BCD Nr

- nr type : 0

- nr plan : 1

- nr : 01772000001

Signalling Examples



32. Setup (BSC to MSC ; L3)

- DTAP (length : 14, 0Eh)


SETUP (CC)

Bearer Capability

- length : 1 (1h)





Called Party BCD Nr

- nr type : 0

- nr plan : 1

- nr : 01772000001 ------------------------------------------------------------------------------------------------

Called Party BCD number

This element contains the called party BCD number. In a normal call, this element contains the dialled digits.

Called Party Number

nr type : d

nr plan : d

nr ddddddddddddddd

The meaning of different values for type of number is:

value type of number

0 Unknown

1 international

2 national

3 network specific

4 dedicate PAD access

Other values are reserved.

The meaning of different values for numbering plan is:

value numpering plan




25 (119)

0 Unknown

1 ISDN/telephony

3 data (X.121)

4 telex (F.69)

8 national

9 private

Other values are reserved.

The digits of the party number are displayed in the order as they apper in the message. Digits from 0 to 9 are displayed as themselves. For other digits the following interpretation shall be used:

Ah ':'

Bh ';'

Ch ''

Fh '?', endmark.

33. Send information for Originated call (MSC to VLR;CCS7)

VLR requests for retrieval of call data.

34. Complete call (VLR to MSC ;CCS7) Call completion acknowledged by VLR for MOC.

35. Call Proceeding (MSC to BSC ; L3)



CALL PROCEEDING (CC) The MSC responds to the Setup message.

36. Call Proceeding (BSC to BTS to MS;BTSM SDCCH L3)

DATA REQ (RLL) T=1

Channel Nr


- timeslot : 1

Link Id


Signalling Examples



- SAPI : 0

L3 Info

CALL PROCEEDING (CC)

37. Assignment Request (MSC to BSC;BSSMAP)


ASSIGNMENT REQUEST

Channel Type

- length : 3 (03h)

- speech

- TCH/FS

- GSM speech encoding algorithm version 1


- length : 2 (02h)




Priority

- length : 1 (01h)

- priority level 3 (3h)

- queueing allowed

- preemption vulnerability indi not allowed

Circuit Identity Code

- pcm multiplex : 1 (001h)

- pcm timeslot : 1 (01h)

This message starts the TCH allocation. In the A- interface, MSC is the master and it hunts the circuit used for this call through the A- interface. This message can contain some optional information according to GSM-recommendations. This optional information is: Priority of the call, Downlink Discontinuous Transmission (DTX), Radio channel identity and Interference band to use.




27 (119)

38. Physical Context Request(BSC to BTS ;BTSM) By using this message, the BSC interrogates the actual timing advance from the BTS in order to start TCH allocation through the Abis -interface.

PHYS. CONTEXT REQ (DCh) T=0

Channel Nr


- timeslot : 1

39. Physical Context Confirm (BTS to BSC ;BTSM) BSC receives the timing advance information from the BTS and starts TCH reservation and allocation. This reservation & allocation procedure is similar to the case of the SDCCH -channel.

PHYS. CONTEXT CNF (DCh) T=0

Channel Nr


- timeslot : 1

BS Power


MS Power


Timing Adv.

- 0 (00h) (0 km

40. Channel Activation (BSC to BTS;BTSM) After the BSC's internal channel reservation and allocation, it activates the TCH by sending this message towards the BTS. Contents: channel number, activation type, channel mode (DTX/No DTX), channel type (Speech / data: if speech, then GSM encoding algorithm included, if data, then information about transparency or non-transparency of the channel and data rate), channel identity, encryption information if received, BS & MS power levels as received in 'Physical context confirm' -message and timing advance.


Channel Nr

- full rate TCH

- timeslot : 6

Signalling Examples



Act. Type

- normal assignment procedure

Channel Mode

- length : 4



Channel Id

- length : 6

- full rate TCH

- timeslot : 6


- hopping : 0


- ARFCN : 92 (5ch)


Encr. Info

- lentgh : 9

- GSM A5/1

- ciphering key : FE 61 95 FE E5 73

32 C8

BS Power


MS Power


Timing Adv.

- 0 (00h) (0 km)

41. Channel Activation Ack (BTS to BSC; BTSM) The BTS returns current TDMA frame number and after that the TCH is activated through the Abis-interface


Channel Nr

- full rate TCH




29 (119)

- timeslot : 6

Frame Number

- N32 : 12 (ch)

- N26 : 14 (eh)

- N51 : 46 (2eh)

42. Assignment Command (BSC to BTS to MS;BTSM SDCCH L3)

The BTS delivers received information further on towards the MS. Contents: channel description, power levels, cell channel description, channel mode (Full / Half) and mobile allocation.

DATA REQ (RLL) T=1

Channel Nr


- timeslot : 1

Link Id


- SAPI : 0

L3 Info

ASSIGNMENT COMMAND (RR)

Channel Description

- full rate TCH

- timeslot : 6


- hopping : 0


- ARFCN : 92 (5ch)

Power Command

- power level of MS : 0

Channel Mode

- speech FR or HR version 1 43. SABM (MS to BTS ;FACCH) This is a Layer 2 message.

Signalling Examples



44. Establish Indication (BTS to BSC ;BTSM) Establish indication -message has two uses. Firstly, when used this phase it points out that from the point of view of the BTS, the MS is now on the FACCH-channel. Thus, the BTS sends information back to the BSC that the MS is now on this kind of FACCH-channel which description is like this etc.

Also the BTS identifies the link = main signalling channel and adds received Layer 3 information into this message. This layer 3 information is coming from the MS, of course. (L3 information is optional)

EST. IND (RLL) T=0

Channel Nr

- full rate TCH

- timeslot : 6

Link Id


- SAPI : 0 45. UA (BTS to MS ;FACCH) UA is normal Level 2 acknowledgement when setting up the Layer 2 level link in LAPDm-protocol.

46. Assignment Complete (MS to BTS to BSC;FACCH BTSM L3)

The MS informs it is now on the TCH and everything is OK.

DATA IND (RLL) T=1

Channel Nr

- full rate TCH

- timeslot : 6

Link Id


- SAPI : 0

L3 Info

ASSIGNMENT COMPLETE (RR)

RR Cause

- normal




31 (119)

47. Assignment Complete (BSC to MSC ; L3) The BSS acknowledges the channel seizure to the MSC.


ASSIGNMENT COMPLETE

RR Cause

- norma

48. RF Channel Release (BSC to BTS ;BTSM) When MS has informed the network it is in the TCH, there is no need to use the SDCCH -channel for this call setup any more. By RF Channel Release procedure it is released.

RF CHANNEL REL. (DCh) T=0

Channel Nr


- timeslot : 1

49. RF Channel Release Ack.(BTS to BSC ;BTSM) The BTS acknowledges the RF Channel Release message.

RF CH. REL. ACK (DCh) T=0

Channel Nr


- timeslot : 1 (Paging the other end;MS power control; ccch load)

50. Alerting (MSC to BSC ; L3) This message is sent to the originating side during call set up to inform that the alerting of the called party has been started.



ALERTING (CC)

Progress Indicator

- value (hex) :E0 88

Signalling Examples



51. Alerting (BSC to BTS to MS ;BTSM FACCH L3) The MSC informs the MS that the called subscriber has been alerted. This message can contain also so-called progress indicator IE, which tells that there are in-band announcements or other similar information to be received. In brief, this means that the connection is not end-to-end ISDN connection. If the MS receives this element, it shall through-connect the speech path. In case it is not, the MS generates ringing tone in itself. This information can also be transferred in a Progress message.

DATA REQ (RLL) T=1

Channel Nr

- full rate TCH

- timeslot : 6

Link Id


- SAPI : 0

L3 Info

ALERTING (CC)

Progress Indicator


52. Connect (MSC to BSC ; L3) The MSC sends a Connect message to the MS via the BSS. This message indicates the MS that a connection has been established through the network.



CONNECT (CC) 53. Connect (BSC to BTS to MS;BTSM FACCH L3) When the MS receives a Connect message, it attaches the user connection to the radio path, returns a Connect Acknowledge message, stops any locally generated alerting indication (if applied) and enters the "active" state.

DATA REQ (RLL) T=1

Channel Nr

- full rate TCH

- timeslot : 6

Link Id




33 (119)


- SAPI : 0

L3 Info

CONNECT (CC)

54. Connect Ack. (MS to BTS to BSC;FACCH BTSM L3)

By using this message, the MS informs the MSC that the MS is now in the "active" state.

DATA IND (RLL) T=1

Channel Nr

- full rate TCH

- timeslot : 6

Link Id


- SAPI : 0

L3 Info

CONNECT ACKNOWLEDGE (CC)

55. Connect Ack. (BSC to MSC ; L3) The message is forwarded to the MSC.



CONNECT ACKNOWLEDGE (CC) This is the point at which speech is connected & conversation starts.

56. Measurement Report (MS to BTS ;SACCH L3) When call is on, the MS sends measurement report concerning mainly the quality of the speech connection two times per second.

57. Measurement Report (BTS to BSC ;BTSM L3) If these measurement reports are pre-processed in the BTS then measurement results are sent towards the BSC. If the is no pre-processing in the BTS, then measurement reports are sent. In this phase, Nokia BTS does not make any pre-processing.

Signalling Examples



MEAS. RES. (DCh) T=0

Channel Nr

- full rate TCH

- timeslot : 6

Meas.Res. Nr

- value : 42 (2ah)

Uplink Meas.

- length : 3 (3h)

- downlink DTX not used

- rxlev_full : 43 (-68 - -67 dBm)

- rxlev_sub : 43 (-68 - -67 dBm)

- rxqual_full : 0

- rxqual_sub : 0

BS Power


L1 Info

- MS power control level : 1 (1h)

- actual TA : 0 (00h) (0 km)

L3 Info

MEASUREMENT REPORT (RR)

Measurement Results

- BCCH allocation sequence number : 0

- DTX was not used

- serving cell rxlev_full : 31 (-80 - -79 dBm)

- serving cell rxlev_sub : 32 (-79 - -78 dBm)

- measurement results are valid

- serving cell rxqual_full : 0

- serving cell rxqual_sub : 0

- no neighbour cell meas results

Conversation




35 (119)

58. Disconnect ( MS to BTS to BSC;BTSM FACCH L3)

This request is sent by MS. Contents: clear end-to-end connection. This message stops the charging concerning this call connection.

DATA REQ (RLL) T=1

Channel Nr

- full rate TCH

- timeslot : 6

Link Id


- SAPI : 0

L3 Info

DISCONNECT (CC)

Cause

- length : 2

- coding standard : GSM

- location : user

- normal event

- cause: normal clearing

Progress Indicator


59. Disconnect (BSC to MSC ; L3) The Disconnect message is forwarded to the MSC.



DISCONNECT (CC)

Cause

- length : 2


- location : user

- normal event


Signalling Examples



Progress Indicator


60. Release (MSC to BSC ; L3) Actual release is coming from the MSC; real call is just about to end.



RELEASE (CC)

Cause

- length : 2


- location : user

- normal event


61. Release ( BSC to BTS to MS;BTSM L3) The Release message is forwarded to the MS.

DATA IND (RLL) T=1

Channel Nr

- full rate TCH

- timeslot : 6

Link Id


- SAPI : 0

L3 Info

RELEASE (CC)

Cause

- length : 2


- location : user

- normal event





37 (119)

62. Release Complete

( MS to BTS to BSC ;BTSM FACCH L3) MS informs that it will release the transaction identifier, i.e. call release is proceeding.

DATA REQ (RLL) T=1

Channel Nr

- full rate TCH

- timeslot : 6

Link Id


- SAPI : 0

L3 Info

RELEASE COMPLETE (CC)

63. Release Complete (BSC to MSC ; L3) The Release Complete message is forwarded to the MSC.



RELEASE COMPLETE (CC)

64. Clear Command (MSC to BSC;BSSMAP) This message is coming from the MSC and releases the associated dedicated resources, i.e. BSSAP connection concerning this call.


CLEAR COMPLETE

65. Channel Release

(BSC to BTS to MS ;BTSM FACCH L3) Deactivation command of the used TCH. This is sent by the BSC towards the MS. Quite often this is also called '3rd layer disconnection'. In case of normal call setup case, the release cause is 'normal'.

DATA REQ (RLL) T=1

Channel Nr

Signalling Examples



- full rate TCH

- timeslot : 6

Link Id


- SAPI : 0

L3 Info

CHANNEL RELEASE (RR)

RR Cause

- normal

66. Deactivate SACCH (BSC to BTS;BTSM) By sending this message to downlink direction, the BSC inhibits system information message sending towards the MS. In fact, there is no use to send/receive any information in the SACCH channel any more, so it will be deactivated.

DEACT. SACCH (DCh) T=0

Channel Nr

- full rate TCH

- timeslot : 6

67. DISC (MS to BTS;FACCH ) The MS send Layer 2 frame DISConnect to uplink direction in order to inform the BTS it is stopping the traffic in the TCH/FACCH.

68. UA (BTS to MS ;FACCH) The BTS acknowledges DISC -frame. Consequences: the MS starts to listen BCCH -channel again and all the Air interface resources are released.

69. Release Indication(BTS to BSC ;BTSM) The BTS informs the BSC that the MS has no more any dedicated Air interface resources (i.e. TCH/FACCH) in use.

REL IND (RLL) T=0

Channel Nr

- full rate TCH

- timeslot : 6

Link Id




39 (119)


- SAPI : 0

70. RF Channel Release (BSC to BTS ;BTSM) The BSC tells the BTS to release the rest of the radio resources.


Channel Nr

- full rate TCH

- timeslot : 6

71. RF Channel Release Ack. All the rest of the radio resources have been released; BTS send an acknowledgement to BSC. These radio resources are TCH/FACCH and SACCH.


Channel Nr

- full rate TCH

- timeslot : 6 72. Clear Complete (BSC to MSC ; BSSMAP) This is acknowledgement to the message SCCP Data (Clear Command). Now the BSC informs the MSC that all radio resources related to this call are released.


CLEAR COMPLETE

73. SCCP Released (MSC to BSC;SCCP) When all radio resources are released, BSSAP connection concerning this call is not needed any more. This message tells the BSC to release this SCCP connection. The message is sent as RLSD message.

RLSD - RELEASED

Routing Label

- DPC : 432 (01B0h) OPC : 12600 (3138h)

- SLC : 11 (0Bh)

Signalling Examples



Destination Local Reference

- 0D8056h

Source Local Reference

- 4B814Ch

Release Cause

- SCCP user originated

74. SCCP Released Ack. (BSC to MSC ;SCCP) BSC informs MSC that now the dedicated SCCP connection concerning this call is released. The message is sent as RLC message.

RLC - RELEASE COMPLETE

Routing Label

- DPC : 12600 (3138h) OPC : 432 (01B0h)

- SLC : 13 (0Dh)


- 4B814Ch


- 0D8056h




41 (119)

2.2 Mobile Terminated Call Signalling Example

MSC BSC BTS MSVLR

Channel Required

Channel Activation

Channel Activation Ack .

Immediate Assigment Command.

Channel Request ( RACH )

Immediate Assigment ( AGCH ).

SABM Paging Response(SDCCH)

Establish IndicationCR (Paging Response)Process Access Request

AuthenticateDT1 Authentication Request

Authentication Request ( SDCCH )

Authentication Response ( SDCCH )DT1 Authentication Response

Authentication Response

Set Ciphering ModeDT1 Ciphering Mode Command

Encryption CommandCiphering Mode Command(SDCCH)

Ciphering Mode Complete ( SDCCH )DT1Ciphering Mode Complete

Access Request Accepted

Forward New TMSITMSI Reallocation Command

TMSI Reallocation Command ( SDCCH )

TMSI Reallocation Complete ( SDCCH )

TMSI Reallocation CompleteTMSI Ack .

Setup ( SDCCH )DT1 SetupComplete IC

DT1 Call ConfirmedCall Confirmed ( SDCCH )

DT1 Assignment RequestPhysical Context RequestPhysical Context Confirmed

Channel Activation

Channel Activation Ack .Assignment Command ( SDCCH )

SABM ( FACCH )Establish Indication

UA ( FACCH )Assignment Complete (FACCH)

DT1 Assignment CompleteRF Channel Release

RF Channel Release Ack .DT1 Alerting Alerting ( FACCH )

DT1 Connect Connect ( FACCH )

Connect Ack .( FACCH )DT1 Connect Ack .

Measurement Report ( SACCH )Measurement Report/Result

Disconnect ( FACCH )DT1 Disconnect

DT1 Release

DT1 Release Complete

DT1 Clear Command

Release ( FACCH )

Release Complete ( FACCH )

Channel Release (FACCH)

Deactivate SACCHDISC ( FACCH )

UA ( FACCH )Release Indication

RF Channel Release

RF Channel Release Ack .DT1 Clear Complete

RLSD ( SCCP Released )

RLC ( SCCP Released Ack .)

Paging RequestPaging CommandUDT Paging1 2 3

456

78 9

101112 13

1415

1617

1819 20

2122

2324

2526

27 2829

3031 32

3334

3536

373839

404142

43444546

4847

49505152

5354 55

565758 59

6061

626364

6566

6768

RADIOACCESSPART

PAGINGPART

UA (SDCCH)

ESTABLISHMENTPART

CIPHERING,AUTHENTICATIONAND CALL SETUPPART

TCH SEIZED

CONVERSATIONPART

RELEASE BY MS

PagingResponse

Send info for IC Call

Page MS

CC

Signalling Examples



1. Paging (MSC to BSC ;BSSMAP) This message is sent by MSC when it has found out the called MS is somewhere under him (= MSC recognises this is a GSM_END -call). This message contains mainly four kind of information: message type, IMSI of the called subscriber, TMSI of the called subscriber and Cell Identifier list. If TMSI -numbers are defined for use these have the priority one, for security reasons and if the network does not use TMSIs then IMSI -number is included only. The paging is sent as an UDT (Unit Data) message to the BSC.

- BSSMAP (length : 28, 1Ch)

PAGING

IMSI

- length : 8 (08h)

- identity contains an IMSI

- mobile country code : 262

- mobile network code : 09

- MSIN : 0000000002

TMSI

- length : 4 (04h)

- TMSI value : CA2A0100h

Cell Identifier List

- length : 9 (09h)



- cell identifier : 173 (00ADh)



2. Paging Command (BSC to BTS ;BTSM) The BSC always calculates so-called paging group. The idea of this calculation is to find out in which radio time slots the BTS can send the Paging Requests out towards the MS. Reason: in the network, there is a possibility to have at least three different kind of BCCH-TRX -radio time slot configurations and thus logical channel PCH can have at least three different kinds of location. If the BSC receives both TMSI and IMSI from the MSC, then it uses always TMSI number when sending paging further on.




43 (119)

PAGING CMD (CCh) T=0

Channel Nr


- timeslot : 0

Paging Group

- value : 2 (02h)

MS Identity

- TMSI : ca2a0100

3. Paging Request (BTS to MS;PCH) The BTS sends paging on a PCH channel.

4. Channel Request ( MS to BTS ;RACH) The MS requests a channel by sending a random access burst on a RACH channel to a BTS. The Channel request message contains the establishment cause (3 bits) which can be response to paging, emergency call or 'other services' e.g. Mobile Originated Call, Short Message Service or Location Update. Additionally, this message contains a Random Reference, which consists of 5 bits randomly selected by the MS. This random reference is used to separate two MSs that are attempting to access the network at exactly the same time.

5. Channel Required (BTS to BSC ;BTSM) The BTS sends a channel-required message to the BSC, which contains the information contained in the channel request. To this, the BTS adds the TDMA frame number and the Access Delay, which is the first timing advance estimate made by the BTS.

CHAN RQD (CCh) T=0

Channel Nr

- uplink CCCH (RACH)

- timeslot : 0

Req. Ref

- answer to paging


- N32 : 10 (ah)

- N26 : 23 (17h)

- N51 : 34 (22h)

Signalling Examples



Access Delay

- value : 0 (00h)

6. Channel Activation (BSC to BTS ;BTSM) After receiving the channel-required message, the BSC allocates an SDCCH -channel for this call. It sends a Channel Activation message to the BTS containing the following parameters: DTX control, channel description, mobile allocation, maximum power levels of the MS and BTS and the timing advance as calculated by the BSC.


Channel Nr


- timeslot : 1

Act. Type

- immediate assignment procedure

Channel Mode

- length : 4



Channel Id

- length : 6

- SDCCH/8 subch 3

- timeslot : 1


- hopping : 0


- ARFCN : 92 (5ch)


BS Power


MS Power


Timing Adv.

- 0 (00h) (0 km)




45 (119)

7. Channel Activation Ack . (BTS to BSC;BTSM) A response to the channel activation message. When the BTS has received this message it starts to send and receive on the SDCCH channel.


Channel Nr


- timeslot : 1

Frame Number

- N32 : 10 (ah)

- N26 : 7 (7h)

- N51 : 44 (2ch)

8. Immediate Assignment Command (BSC to BTS ;BTSM L3)

The BSC tells the BTS about the characteristics of the SDCCH channel to use.

IMM.ASS. CMD (CCh) T=0

Channel Nr


- timeslot : 0

Imm. Ass. Info

- value (hex) : 06 3F 00 59 03 5C 99

54 57 00 00

IMMEDIATE ASSIGNMENT (RR)

Page Mode

- normal paging

Channel Description


- timeslot : 1


- hopping : 0


- ARFCN : 92 (5ch)

Request Reference

Signalling Examples



- answer to paging


- N32 : 10 (ah)

- N26 : 23 (17h)

- N51 : 34 (22h)

Timing Advance

- 0 (00h) (0 km)

Mobile Allocation


9. Immediate Assignment (BTS to MS ;AGCH ) The BTS informs the MS on the AGCH channel the characteristics of the SDCCH channel to be used. Parameters include the page mode, SDCCH channel description, SACCH, hopping indicator, the initial timing advance, and mobile allocation (if frequency hopping applies). Additionally, the request reference (random reference and the TDMA frame number) originally sent by the MS is included to identify the relevant MS. The MS is then able to switch to this SDCCH channel.

------------------------------------------------------------------------------------------------

Page Mode

The purpose of this element is to control the behavour of a mobile belonging to the paging subgroup to which this element is sent.

Page Mode

page text

Paging mode

value page text

0 normal paging

1 extended paging

2 paging reorganisation

3 same as before

10. SABM (MS to BTS ;SDCCH) Paging Response (MS to BTS ; L3)

The MS responds to the paging on the signalling channel.




47 (119)

11. Establish Indication (BTS to BSC ;BTSM) Paging Response (L3)

BTS acknowledges the Immediate Assignment Command by returning Establish Indication message. Establish indication -message has two uses. Firstly, when used in this phase it points out that from the BTS point of view, the MS is now on the SDCCH-channel. Thus, the BTS sends information back to the BSC that the MS is now on this kind of SDCCH-channel which description is like this etc. Also the BTS identifies the link = main signalling channel and adds received Layer 3 information into this message.

EST. IND (RLL) T=0

Channel Nr


- timeslot : 1

Link Id


- SAPI : 0

L3 Info

PAGING RESPONSE (RR)


- value : 2h

MS Classmark 2

- length : 2 (02h)




- frequency band 0


Mobile Identity

- length : 5h

- TMSI : ca2a0100

Signalling Examples



12. Paging Response (BSC to MSC ; SCCP BSSMAP L3)

The BSC initiates the MSC about the connection by paging response, which is a CR (Connection Request) me

CR - CONNECTION REQUEST

Routing Label

- DPC : 12600 (3138h) OPC : 432 (01B0h)

- SLC : 13 (0Dh)


- 7DC056h

Protocol Class

- protocol class : 2h, connection oriented

Called Party Address

- length 2 (02h)

- no global title present

- routing based on SSN and MTP routing label

- subsystem is BSSAP

Calling Party Address

- length 4 (04h)

- no global title present

- routing based on SSN and MTP routing label

- point code : 432 (01B0h)

- subsystem is BSSAP

SCCP User Data

- length 24 (18h)

End of Optional Parametersssage.


COMPLETE L3 INFORMATION

Cell Identifier

- length : 5 (05h)







49 (119)

Layer 3 Information

- length : 12 (0Ch)

PAGING RESPONSE (RR)


- value : 2h

MS Classmark 2

- length : 2 (02h)




Process Access Request (MSC to VLR)

Authentication (VLR to MSC)

13. UA (BTS to MS ;SDCCH ) UA is normal Layer 2 level acknowledgement when setting up the Layer 2 level link in LAPDm -protocol.

-------SCCP-----------

CC - CONNECTION CONFIRM

Routing Label

- DPC : 432 (01B0h) OPC : 12600 (3138h)

- SLC : 12 (0Ch)


- 7DC056h


- 4C814Ch

Protocol Class

- protocol class : 2h, connection oriented

14. Authentication Request (MSC to BSC ;BSSMAP L3) As a CC (Connection Confirmed) message, the MSC sends an Authentication Request message to the BSC. The message contains the RAND.



Signalling Examples





- value : 3h


EE2DF3382E516497A5BE005BDD1B7313

15. Authentication Request (BSC to BTS to MS; BTSM SDCCH L3)

The BSC forwards the message via the BTS to the MS.

DATA REQ (RLL) T=1

Channel Nr


- timeslot : 1

Link Id


- SAPI : 0

L3 Info



- value : 3h


EE2DF3382E516497A5BE005BDD1B7313

16. Authentication Response (MS to BTS to BSC; SDCCH BTSM L3)

The MS responds to the Authentication Request with the Signed Response SRES. The Authentication Response is sent to the BSC via the BTS.In the MS Authentication procedure, two algorithms, A3 and A8 are used. In the SIM -card (In MS), both of these algorithms and 32 -digit key are stored) and the very same information can be found in Authentication Centre (AuC) also. When MS Authentication is requested by the network, AuC/VLR sends 32 -digit RANDom Number to the MS. MS calculates then Signed Response (SRES and returns that back to the VLR. VLR makes a comparison if received SRES is same than it has received inside of the Authentication triplet from the AuC before. If these two SRESs are the same, authentication went OK and MS can continue the call setup. Should you notice, the first 8 digits of the KI are used




51 (119)

for Authentication and SRES calculation, the rest 24 are reserved for Ciphering Key calculation.

DATA IND (RLL) T=1

Channel Nr


- timeslot : 1

Link Id


- SAPI : 0

L3 Info


Auth. Parameter SRES : EE2CF13B

17. Authentication Response (BSC to MSC ;BSSMAP L3)

Inside of this message, the SRES value from the MS is forwarded back to the VLR in order to finalise authentication procedure.

This and all other messages in the A-interface up to the releasing of the SCCP connection are transmitted by using SCCP DT1 (Data Form 1) messages.




Auth. Parameter SRES : EE2CF13B

Authentication Response (MSC to VLR)

Set Ciphering Mode (VLR to MSC)

18. Ciphering Mode Command (MSC to BSC;BSSMAP ) The MSC asks the BSC start ciphering on the radio path. This message is sent in the A-interface in case the network wants to initiate ciphering over the radio interface. If the network uses ciphering then MS starts ciphering after receiving this message.


CIPHER MODE COMMAND


- length : 2 (02h)

Signalling Examples






Encryption Information

- length : 9 (09h)

- GSM user data encr. v. 1

- ciphering key, length : 8 (08h)

2A 54 62 90 5D 47 FA A0

19. Encryption command (BSC to BTS ;BTSM L3) The BSC stores the Encryption information to its memory and sends an Encryption command to the BTS to start ciphering mode operations.

ENCR. CMD (DCh) T=0

Channel Nr


- timeslot : 1

Encr. Info

- lentgh : 9

- GSM A5/1

- ciphering key : 2A 54 62 90 5D 47

FA A0

Link Id


- SAPI : 0

L3 Info

CIPH. MODE COMMAND (RR)

Cipher Mode Setting

- start ciphering

20. Ciphering Mode Command (BTS to MS;SDCCH) The BSS informs the MS about beginning of ciphering , and starts receiving in the ciphered mode.




53 (119)

21. Ciphering Mode Complete (MS to BTS to BSC ;SDCCH BTSM L3)

The MS acknowledges ciphering command.

DATA IND (RLL) T=1

Channel Nr


- timeslot : 1

Link Id


- SAPI : 0

L3 Info

CIPH. MODE COMPLETE (RR)

22. Ciphering Mode Complete (BSC to MSC;BSSMAP) If ciphering is in use, this is the first ciphered message (by the MS) in the Air interface. The BSS acknowledges the Ciphering Command, informs the MSC that MS has started ciphering and starts sending information in ciphered mode.


CIPHER MODE COMPLETE

Access Request Accepted (VLR to MSC)

Forward New TMSI (VLR to MSC)

Identity Request (MSC to BSC to BTS to MS)

Identity Response(MS to BTS to BSC to MSC)

23. TMSI Realloction Command (MSC to BSC;BSSMAP L3)

The purpose of the TMSI reallocation procedure is to provide identity confidentiality. Usually the TMSI reallocation is performed at least at each change of location area. MSC initiates the TMSI reallocation procedure by sending TMSI Reallocation command message to the MS. TMSI Reallocation Command message contains a new combination of TMSI and LAI allocated by the network or a LAI and the IMSI if the used TMSI shall be deleted. Usually the TMSI Reallocation Command message is sent to the MS by using a RR connection in ciphered mode.

- DTAP (length : 13, 0Dh)


Signalling Examples




Location Area Id.

- MCC : 262

- MNC : 09

- LAC : 1369 (559h)

Mobile Identity

- length : 5h

- TMSI : ca2d0100

24. TMSI Reallocation Command (BSC to BTS to MS;BTSM SDCCH L3)

TMSI Reallocation Command is forwarded to the MS.

DATA REQ (RLL) T=1

Channel Nr


- timeslot : 1

Link Id


- SAPI : 0

L3 Info


Location Area Id.

- MCC : 262

- MNC : 09

- LAC : 1369 (559h)

Mobile Identity

- length : 5h

- TMSI : ca2d0100

25. TMSI Realloction Complete (MS to BTS to BSC;SDCCH BTSM L3)

When the MS receives the TMSI Reallocation Command message, it stores the LAI in the SIM. If the received identity is the IMSI of the MS, it deletes any previously stored TMSI. If the received identity is a TMSI, the MS stores it in




55 (119)

the SIM. In both cases the MS send a TMSI Reallocation Complete message to the network.

DATA IND (RLL) T=1

Channel Nr


- timeslot : 1

Link Id


- SAPI : 0

L3 Info

TMSI REALLOC COMPL. (MM)

26. TMSI Reallocation Complete (BSC to MSC ;BSSMAP L3)

TMSI Reallocation Complete message is forwarded to the MSC.



TMSI REALLOC COMPL. (MM) ----------------------------------------------------------------

TMSI Ack. (MSC to VLR)

Complete IC (VLR to MSC)

-----------------------------------------------------------------

27. Setup(MSC to BSC ;BSSMAP L3) After authentication, Identification and Ciphering, the MS is in the SDCCH channel and ready to start real call setup signalling. The MSC sends a Setup message to the BSC to be forwarded to the MS.



SETUP (CC)

Bearer Capability

- length : 1 (1h)




Signalling Examples




28. Setup (BSC to BTS to MS;BTSM SDCCH L3) The BSC sends the Setup message to the MS via BTS in order to inform the MS about the incoming call.

DATA REQ (RLL) T=1

Channel Nr


- timeslot : 1

Link Id


- SAPI : 0

L3 Info

SETUP (CC)

Bearer Capability

- length : 1 (1h)





29. Call Comfirmed (MS to BTS ;SDCCH) The MS responds after having checked the compatibility with a requested bearer capability.

DATA IND (RLL) T=1

Channel Nr


- timeslot : 1

Link Id


- SAPI : 0

L3 Info

CALL CONFIRMED (CC)




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30. Call Confirmed (BSC to MSC ;BSSMAP L3) The information is forwarded to the MSC. This message indicates that the network has received all information that is required for call setup and no more such information will be accepted.



CALL CONFIRMED (CC)

31. Assignment Request (MSC to BSC;BSSMAP) This message starts the TCH allocation. In the A- interface, MSC is the master and it hunts the circuit used for this call through the A- interface. This message can contain some optional information according to GSM- recommendations. This optional information is: Priority of the call, Downlink Discontinuous Transmission (DTX), Radio channel identity and Interference band to use.


ASSIGNMENT REQUEST

Channel Type

- length : 3 (03h)

- speech

- TCH/FS

- GSM speech encoding algorithm version 1


- length : 2 (02h)




Priority

- length : 1 (01h)

- priority level 3 (3h)

- queueing allowed

- preemption vulnerability indi not allowed

Circuit Identity Code

- pcm multiplex : 1 (001h)

- pcm timeslot : 2 (02h)

Signalling Examples



32. Physical Context Request (BSC to BTS ;BTSM) By using this message, the BSC interrogates the actual timing advance from the BTS in order to start TCH allocation through the Abis -interface.

PHYS. CONTEXT REQ (DCh) T=0

Channel Nr


- timeslot : 1

33. Physical Context Confirme (BTS to BSC ;BTSM) BSC receives the timing advance information from the BTS and starts TCH reservation and allocation. This reservation & allocation procedure is similar to the case of the SDCCH -channel.

PHYS. CONTEXT CNF (DCh) T=0

Channel Nr


- timeslot : 1

BS Power


MS Power


Timing Adv.

- 0 (00h) (0 km)

34. Channel Activation (BSC to BTS ;BTSM) After the BSC's internal channel reservation and allocation, it activates the TCH by sending this message towards the BTS. Contents: channel number, activation type, channel mode (DTX/No DTX), channel type (Speech / data: if speech, then GSM encoding algorithm included, if data, then information about transparency or non-transparency of the channel and data rate), channel identity, encryption information if received, BS & MS power levels as received in 'Physical context confirm' -message and timing advance


Channel Nr

- full rate TCH

- timeslot : 7




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Act. Type

- normal assignment procedure

Channel Mode

- length : 4



Channel Id

- length : 6

- full rate TCH

- timeslot : 7


- hopping : 0


- ARFCN : 92 (5ch)


Encr. Info

- lentgh : 9

- GSM A5/1

- ciphering key : 2A 54 62 90 5D 47

FA A0

BS Power


MS Power


Timing Adv.

- 0 (00h) (0 km)

35. Channel Activation Ack. (BTS to BSC ;BTSM) The BTS returns current TDMA frame number and after that the TCH is activated through the Abis-interface.


Channel Nr

- full rate TCH

Signalling Examples



- timeslot : 7

Frame Number

- N32 : 11 (bh)

- N26 : 2 (2h)

- N51 : 2 (2h) 36. Assignment Command

(BSC to BTS to MS;BTSM SDCCH L2) The BTS delivers received information further on towards the MS. Contents: channel description, power levels, cell channel description, channel mode (Full / Half) and mobile allocation

DATA REQ (RLL) T=1

Channel Nr


- timeslot : 1

Link Id


- SAPI : 0

L3 Info

ASSIGNMENT COMMAND (RR)

Channel Description

- full rate TCH

- timeslot : 7


- hopping : 0


- ARFCN : 92 (5ch)

Power Command

- power level of MS : 0

Channel Mode

- speech FR or HR version 1




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37. SABM (MS to BTS ;FACCH) SABM (Set Asynchronous Balanced Mode)

This is Layer 2 message and contains some Layer 3 information. Content of this message: service request (look establishment cause!), ciphering key sequence, Mobile Station Classmark and Mobile Identity.

38. Establish Indication (BTS to BSC ;BTSM) Establish indication -message has two uses. Firstly, when used this phase it points out that from the point of view of the BTS, the MS is now on the FACCH-channel. Thus, the BTS sends information back to the BSC that the MS is now on this kind of FACCH-channel which description is like this etc. Also the BTS identifies the link = main signalling channel and adds received Layer 3 information into this message. This layer 3 information is coming from the MS, of course.

EST. IND (RLL) T=0

Channel Nr

- full rate TCH

- timeslot : 7

Link Id


- SAPI : 0

39. UA (BTS to MS; FACCH ) UA is normal Level 2 acknowledgement when setting up the Layer 2 level link in LAPDm-protocol.

40. Assignment Complete (MS to BTS to BSC ;BTSM FACCH )

The MS informs it is now on the TCH and everything is OK.

DATA IND (RLL) T=1

Channel Nr

- full rate TCH

- timeslot : 7

Link Id


- SAPI : 0

L3 Info

ASSIGNMENT COMPLETE (RR)

Signalling Examples



RR Cause

- normal

41. Assignment complete (BSC to MSC ;BSSMAP) The BSS acknowledges the channel seizure to the MSC.


ASSIGNMENT COMPLETE

RR Cause

- normal

42. RF Channel Release (BSC to BTS ;BTSM) When MS has informed the network it is in the TCH, there is no need to use the SDCCH -channel for this call setup any more. By RF Channel Release procedure it is released.


Channel Nr


- timeslot : 1

43. RF Channel Release Ack.(BTS to BSC ;BTSM) The BTS acknowledges the RF Channel Release message.


Channel Nr


- timeslot : 1

44. Alerting (MS to BTS to BSC;FACCH BTSM L3) The MS sends an Alerting message via BSS.

DATA IND (RLL) T=1

Channel Nr

- full rate TCH

- timeslot : 7

Link Id




63 (119)


- SAPI : 0

L3 Info

ALERTING (CC)

45. Alerting (BSC to MSC;BSSMAP L3) The MS informs that the subscriber has been alerted. This message can contain also so-called progress indicator IE, which tells that there are in-band announcements or other similar information to be received. In brief, this means that the connection is not end-to-end ISDN connection. If the MS receives this element, it shall through-connect the speech path. In case it is not, the MS generates ringing tone in itself. This information can also be transferred in a Progress message.



ALERTING (CC)

46. Connection (MS to BTS to BSC ;BTSM FACCH L3) When the MS receives a Connect message, it attaches the user connection to the radio path, returns a Connect Acknowledge message, stops any locally generated alerting indication (if applied) and enters the "active" state.

DATA REQ (RLL) T=1

Channel Nr

- full rate TCH

- timeslot : 6

Link Id


- SAPI : 0

L3 Info

CONNECT (CC)

47. Connection (BSC to MSC ;BSSMAP L3) The MSC sends a Connect message to the MS via the BSS. This message indicates the MS that a connection has been established through the network.


Signalling Examples




CONNECT (CC)

48. Connection Ack. (MSC to BSC ;BSSMAP L3) The message is forwarded to the MSC.




49. Connection Ack. (BSC to BTS to MS;FACCH BTSM L3)

By using this message, the MS informs the MSC that the MS is now in the "active" state.

DATA IND (RLL) T=1

Channel Nr

- full rate TCH

- timeslot : 6

Link Id


- SAPI : 0

L3 Info


Conversation

50. Measurement Report (MS to BTS ;SACCH L3) When call is on, the MS sends measurement report concerning mainly the quality of the speech connection two times per second.

51. Measurement Report (BTS to BSC ;BTSM L3) If these measurement reports are pre-processed in the BTS then measurement results are sent towards the BSC. If the is no pre-processing in the BTS, then measurement reports are sent. In this phase, Nokia BTS does not make any pre-processing.

MEAS. RES. (DCh) T=0

Channel Nr

abis messages

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