OMF001006 GSM Signaling System BSSAP(BSS) Training 20060531 a 2.0

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OMF001006 GSM Signaling System -

BSSAP(BSS)

ISSUE 2.0


References

31033202-BSS Signaling Analysis

Manual

GSM Specification 0808

GSM Specification 0408


Upon completion this course, you will be

able to:

Understand the structure of BSSAP

message

Distinguish BSSMAP and DTAP

messages

Know some BSSMAP and DTAP

message elements


Chapter 1 Chapter 1 BSSAP Functional StructureBSSAP Functional Structure

Chapter 2 Chapter 2 Typical MessagesTypical Messages

Chapter 3 Chapter 3 BSC Signaling and Interface TracingBSC Signaling and Interface Tracing


BSSAP Functional Structure BSSAP： BSS Application Part

BSSMAP： BSS Management Application Part

DTAP： Direct Transfer Part

− CM

− MM

SCCP： Signaling Connection Control Part

MTP：Message Transfer Part

BSSAP

SCCP

MTP-3

MTP-2

MTP-1


BSSAP Functional Structure

BSS

BSSAP

SCCP

DTAP BSSMAP

Distribution Function

BSSAP

SCCP

DTAP BSSMAP

A-Interface

MSC

MTP MTP

Transmission Equipments for Air Interface

Corresponding BSC Processing Modules

Distribution Function

Corresponding MSC Application and Control Modules


Distribution Sub-layer

To discriminate DTAP and BSSMAP messages

To distribute the DTAP messages to radio link L2 access point

To converge the DTAP messages received from radio link L2 to

A-interface signaling link

Functions of BSSAP Distribution Sub-layerFunctions of BSSAP Distribution Sub-layerFunctions of BSSAP Distribution Sub-layerFunctions of BSSAP Distribution Sub-layer


Components of Distribution Sub-layer

Components of Distribution Sub-Components of Distribution Sub-

layerlayer

Components of Distribution Sub-Components of Distribution Sub-

layerlayer

Octet 1

Octet L

Octet 3

Octet 2

Octet 1

Octet 2

Octet 3

Octet 4

Octet L

DTAP BSSMAP

Identifier Identifier

DLCI

LI LI Length Indicator

L3 L3

Message Message

……

..

L3 Messages

Distribution Data Unit

……

..


DTAP

DTAP takes charge of transferring transparent L3 messages from MS

to MSC or from MSC to MS which BSS will not analyze. It is

transferred between BSS and MSC by using SCCP service class 2

(basic connection-oriented class).

III L3 Information

User data

I Distribution Data Unit

II Length Indication


DTAP Distribution Data Unit

Distribution Data Unit has two parameters:

Discriminator : 00000000

Data Link Connection Identity（ DLCI） :

− To indicate the data link type that should be used on the radio

interface for the messages sent from MSC to BSS

− To indicate the data link type on the radio interface that reports

the message which is sent by BSS to MSC.

Discriminator:

Bit: 8 7 6 5 4 3 2 1

0 0 0 0 0 0 0 D

D=1 stands for transparent transmission (DTAP)


BSSMAP

The transmission of BSSMAP messages upon SCCP is for the

BSSMAP functional entities of both MSC and BSS to exchange

information.

The distribution data unit of BSSMAP messages only has the

discriminator. ‘D’ should be equal to 0 which stands for non-

transparent transmission.

Discriminator:

Bit: 8 7 6 5 4 3 2 1

0 0 0 0 0 0 0 D

D=0 stands for non-transparent transmission (BSSAP)


Chapter 2 Typical MessagesChapter 2 Typical Messages

1.1 BSSMAP Message1.1 BSSMAP Message

1.2 1.2 DTAP MessageDTAP Message


Assignment Request

This message is sent from the MSC to the BSS via the relevant SCCP

connection in order to request the BSS to assign radio resource(s), the

attributes of which are defined within the message.

The message may also include the terrestrial circuit to be used.

INFORMATION ELEMENT REFERENCE DIRECTION TYPE LEN

Message Type 3.2.2.1 MSC-BSS M 1 Channel Type 3.2.2.11 MSC-BSS M 5-10 Layer 3 Header Information 3.2.2.9 MSC-BSS O (3) 4

Priority 3.2.2.18 MSC-BSS O 3 Circuit Identity Code 3.2.2.2 MSC-BSS O (1) 3 Downlink DTX Flag 3.2.2.26 MSC-BSS O (2) 2 Interference Band To Be Used 3.2.2.21 MSC-BSS O 2 Classmark Information 2 3.2.2.19 MSC-BSS O (4) 4-5 Group Call Reference 3.2.2.55 MSC-BSS O (5) 3-8 Talker Flag 3.2.2.54 MSC-BSS O (6) 1 Configuration Evolution Indication 3.2.2.57 MSC-BSS O (7) 2


Assignment Complete The ASSIGNMENT COMPLETE message is sent from the BSS to the MSC

and indicates that the requested assignment has been completed correctly.

The message is sent via the BSSAP SCCP connection associated with the

dedicated resource(s).


Message Type 3.2.2.1 BSS-MSC M 1

RR Cause 3.2.2.22 BSS-MSC O 2

Circuit Identity Code 3.2.2.2 BSS-MSC O (4) 3

Cell Identifier 3.2.2.17 BSS-MSC O (1) 3-10

Chosen Channel 3.2.2.33 BSS-MSC O (3) 2

Chosen Encryption Algorithm 3.2.2.44 BSS-MSC O (5) 2

Circuit Pool 3.2.2.45 BSS-MSC O (2) 2

Speech Version (Chosen) 3.2.2.51 BSS-MSC O (6) 2

LSA Identifier 3.2.2.15 BSS-MSC O (7) 4


Assignment Failure

The ASSIGNMENT FAILURE message is sent from the BSS to

the MSC via the relevant SCCP connection. It indicates that

there has been a failure in the assignment process at the BSS

and that the assignment procedure has been aborted.



Cause 3.2.2.5 BSS-MSC M 3-4



Circuit Pool List 3.2.2.46 BSS-MSC O (2) V


Handover Required This message is sent from the BSS to the MSC to indicate that for a given

MS which already has dedicated radio resource(s) assigned, a handover is

required for the reason given by the cause element.


dedicated resource(s). INFORMATION ELEMENT REFERENCE DIRECTION TYPE LEN



Response Request 3.2.2.28 BSS-MSC O 1

Cell Identifier List (Preferred)

3.2.2.27

BSS-MSC

M 2n+3 to

7n+3


Current Channel Type 1 3.2.2.49 BSS-MSC O (2) 2

Speech Version (Used) 3.2.2.51 BSS-MSC O (3) 2

Queueing Indicator 3.2.2.50 BSS-MSC O 2

Old BSS to New BSS Information 3.2.2.59 BSS-MSC O 2-n


Handover Request This message is sent from the MSC to the BSS via the relevant SCCP

connection to indicate that the MS is to be handed over to that BSS. INFORMATION ELEMENT REFERENCE DIRECTION TYPE LEN

Message Type 3.2.2.1 MSC-BSS M 1

Channel Type 3.2.2.11 MSC-BSS M 5-10

Encryption Information 3.2.2.10 MSC-BSS M (1) 3-n

Classmark Information 1 Or 3.2.2.30 MSC-BSS M# 2

Classmark Information 2 3.2.2.19 MSC-BSS M (6) 4-5

Cell Identifier (Serving) 3.2.2.17 MSC-BSS M 5-10

Priority 3.2.2.18 MSC-BSS O 3

Circuit Identity Code 3.2.2.2 MSC-BSS O (7) 3

Downlink DTX Flag 3.2.2.26 MSC-BSS O (3) 2

Cell Identifier (Target) 3.2.2.17 MSC-BSS M 3-10

Interference Band To Be Used 3.2.2.21 MSC-BSS O 2

Cause 3.2.2.5 MSC-BSS O (9) 3-4

Classmark Information 3 3.2.2.20 MSC-BSS O (4) 3-14

Current Channel type 1 3.2.2.49 MSC-BSS O (8) 2

Speech Version (Used) 3.2.2.51 MSC-BSS O (10) 2

Group Call Reference 3.2.2.55 MSC-BSS O (5) 3-8

Talker Flag 3.2.2.54 MSC-BSS O (11) 1

Configuration Evolution Indication 3.2.2.57 MSC-BSS O (12) 2

Chosen Encryption Algorithm (Serving) 3.2.2.44 MSC-BSS O (2) 2

Old BSS to New BSS Information 3.2.2.59 MSC-BSS O(13) 2-n

LSA Information 3.2.2.23 MSC-BSS O(14) 3+4n


Handover Request Acknowledge This message is sent from the BSS to the MSC and indicates that the

request to support a handover at the target BSS can be supported by the

BSS, and also to which radio channel(s) the MS should be directed.


dedicated resource.



Layer 3 Information 3.2.2.24 BSS-MSC M (1) 11-n





Circuit Identity Code 3.2.2.2 BSS-MSC O (3) 3



Handover Command

This message is sent from the MSC to the BSS via the relevant

SCCP connection and contains the target channel to which the

MS should retune.



Layer 3 Information 3.2.2.24 MSC-BSS M (1) 11-n

Cell Identifier 3.2.2.17 MSC-BSS O 3-10


Handover Required Reject

This message is sent from the MSC to the BSS via the relevant

SCCP connection. It indicates to the BSS that the HANDOVER

REQUIRED message has not resulted in handover.



Cause 3.2.2.5 MSC-BSS M 3-4


Handover Complete

This message is sent from the BSS to the MSC via the relevant SCCP

connection.

It indicates that the correct MS has successfully accessed the target cell.





Handover Failure

This message is sent from the BSS to the MSC via the relevant

SCCP connection. It indicates to the MSC that there has been

a failure in the resource allocation process on handover, and

that the handover has been aborted.








Handover Performed

This message is sent from the BSS to the MSC in order to indicate that the

BSS has performed an internal handover. The cell identifier and (if required for O and M reasons) optionally the new

channel identity is included. The message is sent via the BSSAP SCCP connection associated with the

dedicated resource(s). INFORMATION ELEMENT REFERENCE DIRECTION TYPE LEN



Cell Identifier 3.2.2.17 BSS-MSC M 3-10






Paging

This message is sent from the MSC to the BSS and contains

sufficient information to allow the paging message to be transmitted

by the correct cells at the correct time.

This message is sent as a connectionless SCCP message.



IMSI 3.2.2.6 MSC-BSS M 3-10

TMSI 3.2.2.7 MSC-BSS O (1) 6

Cell Identifier List 3.2.2.27 MSC-BSS M 3 to

3+7n

Channel Needed 3.2.2.36 MSC-BSS O (2) 2

eMLPP Priority 3.2.2.56 MSC-BSS O (3) 2


Clear Request

This message is sent from the BSS to the MSC to indicate to the

MSC that the BSS wishes to release the associated dedicated

resource(s).

The message is sent via the BSSAP SCCP connection associated

with the dedicated resource(s).





Clear Command

This message is sent from the MSC to the BSS to instruct the

BSS to release the associated dedicated resource(s).

The message is sent via the BSSAP SCCP connection

associated with the dedicated resource(s).



Layer 3 Header Information 3.2.2.9 MSC-BSS O (1) 4

Cause 3.2.2.5 MSC-BSS M 3-4


Complete Layer 3 Information

The message is sent from the BSS to the MSC on receipt of the initial layer

3 message on a dedicated channel, e.g. Paging response, Location

Updating Request, CM Reestablishment Request, CM Service Request,

IMSI detach. The BSS does not analyse the contents of the initial layer 3 message, other

than the Classmark information. The message is sent via the BSSAP SCCP connection established for the

associated dedicated resource(s).



Cell Identifier 3.2.2.17 BSS-MSC M 3-10

Layer 3 Information 3.2.2.24 BSS-MSC M 3-n


LSA Identifier List 3.2.2.16 BSS-MSC O (2) 2+3n


Chapter 2 Typical MessagesChapter 2 Typical Messages

1.1 BSSMAP Message1.1 BSSMAP Message

1.2 1.2 DTAP MessageDTAP Message


Location Updating Accept

This message is sent by the network to the mobile station to indicate

that updating or IMSI attach in the network has been completed.

IEI Information element Type / Reference Presence Format Length

Mobility management

protocol discriminatorProtocol discriminator/10.2 M V 1/2

Skip Indicator Skip Indicator/10.3.1 M V 1/2

Location Updating Accept

message typeMessage type/10.4 M V 1

Location area

identification

Location area

identification/10.5.1.3M V 5

17 Mobile identity Mobile identity/10.5.1.4 O TLV 3-10

A1 Follow on proceedFollow on

proceed/10.5.3.7O T 1

A2 CTS permission CTS permission/10.5.3.10 O T 1


Location Updating Reject

This message is sent by the network to the mobile station to indicate

that updating or IMSI attach has failed.


Mobility management

protocol discriminator

Protocol discriminator

10.2

M V 1/2

Skip Indicator Skip Indicator

10.3.1

M V 1/2

Location Updating

Reject message type

Message type

10.4

M V 1

Reject cause Reject cause

10.5.3.6

M V 1


Disconnect (network to mobile station direction)

This message is sent by the network to indicate that the end-to-end

connection is cleared.


Call controlprotocol discriminator

Protocol discriminator10.2

M V 1/2

Transaction identifier Transaction identifier10.3.2

M V 1/2

Disconnectmessage type

Message type 10.4 M V 1

Cause Cause 10.5.4.11 M LV 3-31

1C Facility Facility 10.5.4.15 O TLV 2-?

1E Progress indicator Progress indicator10.5.4.21

O TLV 4

7E User-user User-user10.5.4.25

O TLV 3-131

7B Allowed actions $(CCBS)$ Allowed actions10.5.4.26

O TLV 3


Disconnect (mobile station to network direction)

DisconnectDisconnect

This message is sent by the mobile station to request the network to clear an end-to-end connection.

The message contents are similar to those of “Disconnect (network to mobile station direction) “


Setup (mobile originating call establishment)

This message is sent from the mobile station to the network to initiate

a mobile originating call establishment.IEI Information element Type / Reference Presence Format Length

Call controlprotocol discriminator

Protocol discriminator10.2

M V 1/2

Transaction identifier Transaction identifier10.3.2

M V 1/2

Setupmessage type

Message type10.4

M V 1

D- BC repeat indicator Repeat indicator10.5.4.22

C TV 1

04 Bearer capability 1 Bearer capability10.5.4.5

M TLV 3-15

04 Bearer capability 2 Bearer capability10.5.4.5

O TLV 3-15

1C

Facility (simple recall alignment) Facility10.5.4.15

O TLV 2-

5D Calling party sub-address

Calling party subaddr.10.5.4.10

O TLV 2-23

5E Called party BCDnumber

Called party BCD num.10.5.4.7

M TLV 3-43

6D Called party sub-address

Called party subaddr.10.5.4.8

O TLV 2-23


Means of BSC Signaling and Interface Tracing

Signaling analyzer

MA10

KC1297

BSC Maintenance Console

GSM Interface Tracing

GSM Interface Tracing Review

NO7 Message Tracing

NO7 Message Tracing Review


Comparison of different means

Signaling Analyzer

Expensive, additional investment needed.

Can trace all the signaling of A-interface and Abis-interface f

rom the physical layer.

GSM Interface Trace

No additional equipment and investment needed.

A-interface trace – to trace BSSAP and SCCP in BSC.

A-bis interface trace – to trace A-bis interface L3 messages.

Um interface trace – to trace Um interface L3 messages.


Relevant GSM Specifications

GM 0808： A interface

GM 0858： A-bis interface

GM 0408： Um interface

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OMF001006 GSM Signaling System BSSAP(BSS) Training 20060531 a 2.0

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Transcript of OMF001006 GSM Signaling System BSSAP(BSS) Training 20060531 a 2.0