System Management Transfer Project 28 February, 2003 Page 1 /51
A-INTERFACE
GENERAL INFORMATION
System Management Transfer Project 28 February, 2003 Page 2 /51
Interfaces to MSC/VLR
MSC/VLR
MSC VLR
RNS
RNC
NodeB
MSC/VLR
MSCVLR
MSC/VLR
MSCVLR
HLR
SGSN
EIR
GMSC
A-I/fGs-I/f
G-I/f
D-I/fC-I/f
F-I/f
E-I/f
BSSAP
BSSAP+
MAP
MAPMAP MAP
MAP
BSS
BSC
BTS
Iur-I/f RANAP
RNC
NodeB
Iu-I/f
System Management Transfer Project 28 February, 2003 Page 3 /51
TS GSM 48.001 General Aspects
48.002 Interface Principles48.004 Layer 1 - Specification48.006 Signaling Transport Mechanism48.008 Layer 3 Specification48.020 Rate Adaptation on the BSS-MSC Interface
System Management Transfer Project 28 February, 2003 Page 4 /51
TS GSM 48.002 INTERFACE PRINCIPLES
Principles which 48.0x technical specification series are based, e.g.
– BSS (BSC+BTS) is considered as a whole– 1 or more 2048 kbit/s digital transmission– Layered signalling– Channel bit rate 64 kbit/s at MSC boundary, considering
net radio path traffic channel rate less than 16 kbit/s (transcoders)
System Management Transfer Project 28 February, 2003 Page 5 /51
MSC Functions– Terrestrial channel allocation– Blocking of terrestrial channels– TCH channel release– DCCH channel release– Channel coding decoding– Interworking function (data calls)– Traffic measurements– Handover– Mobility management– Call control– Encryption
System Management Transfer Project 28 February, 2003 Page 6 /51
Signaling protocol reference model
Distribution Function
DTAP BSSMAP
SCCP
MTP
Physical Layer
Applications e.g. call control
DTAP Direct Transfer Application Part
+
BSSMAP BSS Management Application Part
=
BSSAP BSS Application Part
System Management Transfer Project 28 February, 2003 Page 7 /51
Network MS
MSC/VLR
BSS/RNS
BSSMAP
Initial MS/UE message
DTAP/NAS
SMS Message
Messages and logical difference
RANAP
System Management Transfer Project 28 February, 2003 Page 8 /51
TS GSM 48.004 LAYER 1 SPECIFICATION
Defines structure of physical layer for supporting traffic channels
– 32 * 64 kbit/s time slots (E1)– 24 * 64 kbit/s time slots (T1)– Refers to CCITT recommendations and ANSI
specifications
System Management Transfer Project 28 February, 2003 Page 9 /51
TS GSM 48.006 SIGNALLING TRANSPORT MECHANISM FOR MSC-BSC INTERFACE
Defines the subsets of MTP, and SCCP and its use– MTP provides a mechanism giving reliable transfer of
signaling messages– SCCP provides a referencing mechanism to identify a
particular transaction relating to for instance a particular call. The SCCP can also be used to enhance the message routing
MTP– E1 links: CCITT Recommendations Q.701, Q.702, Q.703,
Q.704, and Q.707– T1 links: ANSI Specifications T1.111
with stated exceptions
System Management Transfer Project 28 February, 2003 Page 10 /51
SCCP – E1 links: CCITT Recommendations Q.711, Q.712, Q.713,
and Q.714– T1 links: ANSI Specifications T1.112.1-4
with stated exceptions– Not used SCCP functions: error detection, receipt
confirmation, flow control
System Management Transfer Project 28 February, 2003 Page 11 /51
Use of the SCCP– User function is BSSAP– One signaling connection per active mobile station
having one or more transactions for the transfer of layer 3 messages
– BSSMAP: Both connectionless and connection-oriented procedures
– DTAP: Connection-oriented procedures– Distribution Function
Distribution Data Unit: Discrimination Parameter, bit D
– D=0: BSSMAP message– D=1: DTAP message
System Management Transfer Project 28 February, 2003 Page 12 /51
ADDRESSING
SSN + SPC or SSN onlyNo global title is used
System Management Transfer Project 28 February, 2003 Page 13 /51
TS GSM 48.008
LAYER 3 SPECIFICATION
System Management Transfer Project 28 February, 2003 Page 14 /51
GENERAL
Specifies Layer 3 procedures used on BSS-MSC interface for control of GSM services
Call control and mobility management messages and procedures (DTAP) are described in GSM TS 04.08/3GPP TS 24.008
BSSMAP
System Management Transfer Project 28 February, 2003 Page 15 /51
MAIN PARTS
BSSMAP proceduresMessage formats and codingSignalling element codingSignalling diagrams
System Management Transfer Project 28 February, 2003 Page 16 /51
BSSMAP PROCEDURES
General informationSuccessful/unsuccessful operationAbnormal conditions
System Management Transfer Project 28 February, 2003 Page 17 /51
MESSAGE FORMATS AND CODING
Short descriptionInformation elementReferenceDirectionType (mandatory, optional)Length
System Management Transfer Project 28 February, 2003 Page 18 /51
SIGNALLING ELEMENT CODING
Short descriptionStructure of the IE
– element identifier– length– value
System Management Transfer Project 28 February, 2003 Page 19 /51
SIGNALLING DIAGRAMS
Sequence diagrams for the BSSMAP proceduresRelated to an unique procedure
System Management Transfer Project 28 February, 2003 Page 20 /51
Block
Blocking Acknowledge
Circuit Group Block
Circuit Group Blocking Acknowledge
Circuit Group Unblock
Circuit Group Unblocking Acknowledge
Paging
Reset
Reset Acknowledge
Reset Circuit
Reset Circuit Acknowledge
Unblock
Unblocking Acknowledge
Unequipped Circuit
MS
C/V
LR
BS
C
Connectionless BSSMAP messages between BSC and MSC/VLR
System Management Transfer Project 28 February, 2003 Page 21 /51
Assignment Request
Cipher Mode Complete
Classmark Request
Classmark Update
Assignment Complete
Cipher Mode CommandM
SC
/VL
R
BS
C
Connection oriented BSSMAP messages between BSC and MSC/VLR
Assignment Failure
Cipher Mode Reject
Clear Command
Clear Complete
Clear Request
Complete Layer 3 Information
Queuing Indication
System Management Transfer Project 28 February, 2003 Page 22 /51
Handover Command
Handover Detect
MS
C/V
LR
BS
C
Connection oriented BSSMAP messages between BSC and MSC/VLR
Handover Complete
Handover Failure
Handover Performed
Handover Required
Handover Request
Handover Request Acknowledge
Handover Required Reject
System Management Transfer Project 28 February, 2003 Page 23 /51
MSC Invoke Trace
MS
C/V
LR
BS
C
Connection oriented BSSMAP messages between BSC and MSC/VLR
Connection Oriented Information
Connection Oriented Information
SAPI ‘n’ Reject
Trace Invocation
Perform Location Request
Perform Location Response
System Management Transfer Project 28 February, 2003 Page 24 /51
BS
C
MS
C/V
LR
MS
DTAP Messages for Mobility Management
Authentication Response
Authentication Request
Authentication Reject
CM Service Accept
CM Service Abort
CM Service Reject
CM Service Request
Identity Request
Identity Response
Location Updating Accept
Location Updating Reject
IMSI Detach Indication
TMSI Reallocation Command
TMSI Reallocation Complete
System Management Transfer Project 28 February, 2003 Page 25 /51
/// BSSAP
System Management Transfer Project 28 February, 2003 Page 26 /51
FS A-Interface Application Parts in MSC/VLR Server
Main A-Interface FS1/15517-1/APT 21026/2 Lists the sectionsThe use of SCCP
- Addressing- CO and CL services
BSSAP message and IE structure
System Management Transfer Project 28 February, 2003 Page 27 /51
A-Interface, Section A: Location Updating, IMSI Attach and IMSI Detach Procedures
A-Interface, Section B: Basic Call Control ProceduresA-Interface, Section C: Call Related Supplementary
Service ProceduresA-Interface, Section D: Call Independent
Supplementary Service ProceduresA-Interface, Section E: Parallel Transaction ProceduresA-Interface, Section F: Short Message Service
ProceduresA-Interface, Section G: Base Station System
Management Application Part ProceduresA-Interface, Section P: Location Services Procedures
FSs for Signalling Procedures
System Management Transfer Project 28 February, 2003 Page 28 /51
A/Iu-Interface, Section R: UMTS to GSM Inter-
System Handover Procedures A/Iu-Interface, Section S: GSM to UMTS Inter-
System Handover Procedures
System Management Transfer Project 28 February, 2003 Page 29 /51
FSs for Formats and Coding of Messages
A-Interface, Section H: Base Station System Management Application Part, BSSMAP, Message Formats and Coding
A/Iu-Interface, Section I: DTAP and RANAP/NAS, Message Formats and Coding for Mobility Management
A-Interface, Section J: Direct Transfer Application Part, DTAP, Message Formats and Coding for Short Message Service
A/Iu-Interface, Section K: DTAP and RANAP/NAS, Message Formats and Coding for Call Control and Call Related Supplementary Service Procedures
A-Interface, Section L: Direct Transfer Application Part, DTAP, Message Formats and Coding for Call Independent Supplementary Service Procedures
A-Interface, Section M: Supplementary Service ProtocolA-Interface, Section Q: Location Services Protocol
Formats and Coding
System Management Transfer Project 28 February, 2003 Page 30 /51
FS A-interface, Section G: BSSMAP Procedures
Specifies BSSMAP signalling sequences between MSC/VLR Server and BSS/UE
All supported BSSMAP proceduresTime supervisions
System Management Transfer Project 28 February, 2003 Page 31 /51
FS A-interface, Section H: BSSMAP Message Formats and Coding
Lists all supported messages, IEsDescribes Error handlingAdditionally compared with TS 48.008
– GSM phase information– notes about the use of IEs
System Management Transfer Project 28 February, 2003 Page 32 /51
ERROR HANDLING
In case of inconsistent message length between delivered message length according to SCCP and BSSAP header message length, the BSSAP header message length has higher priority
Messages with faulty BSSAP header are ignored. Messages are ignored if they are not consistent
with the Signalling Type (CL, CO), with the direction, or with the recipient’s state
Not recognized or not implemented messages are ignored.
The information elements are classified into conditional, essential, non-essential, and transparent types:
System Management Transfer Project 28 February, 2003 Page 33 /51
Messages containing an unrecognisable or unexpected IE before the last essential IEs are rejected with the cause 'Invalid message' if a reject message exists. If no reject message exists the message is ignored
Messages containing an unrecognisable IE or unexpected IE, after the last essential IEs have been received, are accepted
Messages with a missing essential information element are rejected with the cause 'Invalid message' if a reject message exists. If no reject message exists the message is ignored
Messages with a missing non-essential IE are accepted
System Management Transfer Project 28 February, 2003 Page 34 /51
If the MSC/VLR receives a message and diagnoses a missing conditional IE or an unexpected conditional IE or when it receives a message containing at least one syntactically incorrect conditional and non-transparent IE which is required to be present, then the message will be rejected with the cause 'Invalid Message' if a reject message exists. If no reject message exists the message is ignored
Messages that have an essential and non-transparent IE with field having an incorrect value are rejected if applied with the cause 'Invalid message'. If no reject message exists, the message is ignored
Messages that have a non-essential IE with fields having incorrect value are accepted. IE is ignored
Transparent IEs are not checked
System Management Transfer Project 28 February, 2003 Page 35 /51
MMS FUNCTION SPECIFICATIONS
Administration and Handling of A-Interface Lines in MSC/VLR
– The purpose of this function is to give the operation and maintenance staff the ability to define and supervise A-interface lines
– The A-interface lines are the channels on the trunk between the MSC/VLR Server and the BSC
– The A-interface line can be configured according to ITU-T specifications or ANSI specifications.
Administration of BSC Data in MSC/VLR– This function allows the operation and maintenance
staff to administer BSC data by means of exchange commands
System Management Transfer Project 28 February, 2003 Page 36 /51
– The administration of BSC data includes the following commands
Definition of BSCChange of BSC capabilities Connection of alternative route to a BSCDisconnection of alternative route from a BSCRemoval of BSC Printing of BSC data
Administration of Cell Data in MSC/VLR Server– For this function, two function specifications exist. The
function specification to be ordered depends on the ordering information. Either administration of cell data is supported or administration of both location area data and cell data is supported.
Assignment of Radio Channels in MSC/VLR Server– The Function Specification describes the radio channel
assignment and release procedures for signaling channel assignment and traffic channel assignment over A-interface
System Management Transfer Project 28 February, 2003 Page 37 /51
Circuit Pools for A-interface in MSC/VLR– This function groups, by means of commands, circuits
supporting the same channel type characteristics into circuit pools in the MSC/VLR server.
– It enables the MSC/VLR Server to interwork with BSC which control different transcoder and rate adaptor units (TRAU) connected to different A-interface lines
– This function selects a circuit in an adequate circuit pool at channel assignment or handover when it is ordered by the MSC/VLR Server or when it is requested by the BSC due to circuit pool handling reasons.
System Management Transfer Project 28 February, 2003 Page 38 /51
FUNCTION DESCRIPTIONS
A-Interface Line Terminal Functions– The A-interface line terminal functions allow the seizure
and release of an A-interface line (device) towards a BSS. The function also takes care of the administration of A-interface lines
– The A-interface line terminal functions handle BSSAP messages, concerning A-interface lines (block, unblock, circuit group block, circuit group unblock, reset circuit, unequipped circuit)
– The type of signaling used for the A-interface is ITU-T or ANSI signaling for the SCCP and Message Transfer Part (MTP)layers
– The A-interface line terminal functions take care of the handling of transmission concerning A-interface lines (A-law or U-law idle pattern sending, 24-channel(T1) or 32-channel(E1) Pulse Code Modulation (PCM) Interface or SDH/STM-1 interface)
System Management Transfer Project 28 February, 2003 Page 39 /51
Administration of BSCs– Administration of BSCs is a part of the administration
of Base Station subsystem data in MSC/VLR Server
Administration of Cells– The administration of the cells is performed by means
of seven commands, if the Location Area (LA) administration is supported, and four commands, if the LA administration is not supported. The LA administration involves the definition of a LA before the definition of the cells to be connected to it, and removal of a LA after all cells are removed from this LA
Administration of Circuit Pools for A-Interface– This function is responsible for the administration of
the circuit pools for A-interface
Assignment of Radio Channels in MSC/VLR– This function handles the assignment request, and
possible repetition assignment request due to circuit pool handling, of a traffic channel or a dedicated signalling channel, when requested by other functions
System Management Transfer Project 28 February, 2003 Page 40 /51
MM Transaction Establishment in MSC/VLR– The MM transaction establishment function establishes
the transaction of internal AXE links between the upper layer (CM) and the lower layer (RR). It distributes messages and signals coming from the link in both directions, to the proper user function
MM Connection Management– The MM connection management function establishes,
maintains and releases internal links between the upper layer (CM) and the lower layer (RR), after a first transaction has been established. It distributes messages and signals coming from the link in both directions, to the proper user function
MM Traffic– Takes part for instance packing and unpacking of MM
messages
Monitoring of Mobile Subscribers, A-interface Lines and Iu Connections in MSC/VLR
– This function describes the implementation of monitoring in the MMS subsystem.
System Management Transfer Project 28 February, 2003 Page 41 /51
Packing and Unpacking of Messages on RR Level– The function packs and unpacks all BSSAP messages
related to the radio resources level
RR & SCCP Connection Management– This function is responsible for the following actions:
Establishment and release of SCCP and Rrconnections
Distribution of BSSMAP messages received from SCCP to the appropriate user function
Forwarding of Direct Transfer Application Part (DTAP) messages received from SCCP to the 'MM connection management' function
Sending of BSSMAP messages from user functions or DTAP messages from function 'MM-connection management'to SCCP
Sending, reception and distribution of connectionless messages
Handling of process at reception of a RESET message from a BSC
System Management Transfer Project 28 February, 2003 Page 42 /51
BLOCKS
DIPST (Digital Path Supervision and Test)– The Function block DIPST contains functions for Digital Path
(DIP) administration and maintenance, as well as hardware and clock reference administration
DIPHID (Digital Path Historical Data)– The function block contains functions for historical data
administration
ET (Exchange Terminal function)– Function block ET handles the hardware supervision of
Exchange Terminal Circuit (ETC) and takes part in the supervision of DIP. It also handles the connection/disconnection of the Exchange Module (EM) and Switching Network Terminal (SNT)
ETDIF (Exchange Terminal - Device InterFace)– ETDIF is an interface block between a Device Owner, in this
case MALT, and SNT owner ET. This function is needed for ET155
System Management Transfer Project 28 February, 2003 Page 43 /51
MALT (Mobile Telephony A-interface Line Terminal)– MALT owns the A-Interface lines, it handles the selection
and the release of devices, performs actions as blocking, deblocking and reset of the devices according to the reception of messages from the BSS. The block can send BSSAP messages to acknowledge or initiate actions. For remote A-interface MRALT and MRALTM are the corresponding blocks.
MALTC (Mobile Telephony A-interface Line Terminal Co-ordinator)
– MALTC co-ordinates together with MBSCA the administration of alternative routes (of different device types) to a BSC. The block is also involved in traffic handling by co-ordinating the selection of alternative routes at seizure of A-interface line, when the main route is congested.
MLABT (Mobile Telephony Line Terminal Label Translation)
– MLABT handles the translation of the BSS pointer and Circuit Identity Code (CIC) into a device number and a device block.
System Management Transfer Project 28 February, 2003 Page 44 /51
MMMMH (Mobile Telephony Mobility Management Message Handler)
– MMMMH performs the packing and unpacking of all BSSAP messages related to the mobility management level
MMMSAMH (Mobile Telephony Mobility Management Satellite Application Message Handler)
– The function block MMMSAMH performs analysis,packing and unpacking of Global Satellite System specific MM IEs
System Management Transfer Project 28 February, 2003 Page 45 /51
MRRM complex (Mobile Telephony Radio Resources Management, /MRRM, MRRMASG, MRRMHO/)
– MRRM supervises the establishment and the release of the signaling connections between the MSC/VLR server and the BSC, and handles the messages
– At the reception of the messages, MRRM checks and distributes the different messages to the appropriate user function. The transparent messages (DTAP) are forwarded to the block MMM. The BSSMAP messages, received from MSCCO in connection-oriented mode or from MSCCL in connectionless mode are distributed to the appropriate function on RR level which will initiate the unpacking of the message and take the appropriate action
– In the connection oriented mode, MRRM receives the sending signals from the upper layer for DTAP messages or from MRRMH for BSSMAP messages and forwards them to MSCCO.
System Management Transfer Project 28 February, 2003 Page 46 /51
-In the connectionless mode at message sending stage, MRRM does not act-The block is also involved in several BSSMAP procedures during the assignment of a terrestrial line, the BSC recording initiation process, the ciphering process, the handover and the global reset.
System Management Transfer Project 28 February, 2003 Page 47 /51
MRRMH (Mobile Telephony Radio Resources Message Handler)
– MRRMH is used for unpacking of incoming BSSMAP messages at message reception and for packing of outgoing BSSMAP messages at message sending
MRRRSMH (Mobile Telephony Radio Resources Regional Satellite Application Message Handler)
– The function block MRRRSMH is responsible for the analysis, packing and unpacking of Regional Satellite application specific Ies included in RR layer messages
MRRSAMH (Mobile Telephony Radio Resources Satellite Application Message Handler)
– The function block MRRSAMH is responsible for the analysis, unpacking and packing of Global Satellite System Specific RR IEs
System Management Transfer Project 28 February, 2003 Page 48 /51
MSCCL (Mobile Telephony SCCP Connectionless Signaling)
– MSCCL is used to provide the connectionless message service between the MSC/VLR server and the BSC. It handles the interface between MMS and CCS (SCCP) subsystems
MSCCO (Mobile Telephony SCCP Connection Oriented Signaling)
– MSCCO transfers connection oriented messages between the MSC/VLR server and a BSC.
System Management Transfer Project 28 February, 2003 Page 49 /51
Remote A-interfaceIntroduced in MSC R10
System Management Transfer Project 28 February, 2003 Page 50 /51
TSC/GMSCServer
Site
MSCServer
Site
BSCBTSTDM: BSS A
MAPMAP
BICC CS2
GCP GCP
HLR
ATM or IPConnectivityNetwork
MGWSGW
MGWSGW
What is the aim of this function?
Simply said: to use stand alone (Cello) media gateway for GSM
System Management Transfer Project 28 February, 2003 Page 51 /51
MLABT MALTC
ET MALT ETDIF
DIPST DIPHID
Local BSC TrunkInt.
MLABT
MRALT TAF
Remote BSC TrunkInt.
MMS blocks for local and remote BSC connection