Engineering:Cellular data communication protocol

The protocols described here are from different cellular data communication protocols.

BSMAP

The Base Station Management Application Part (BSMAP) supports all Radio Resource Management and Facility Management procedures between the MSC and the BS, or to a cell(s) within the BS. BSMAP messages are not passed to the MS, but are used only to perform functions at the MSC or the BS. A BSMAP message (complete layer 3 information) is also used together with a DTAP message to establish a connection for an MS between the BS and the MSC, in response to the first layer 3 interface message sent by the MS to the BS for each MS system requests.

BSSLAP

BSSLAP defines the SMLC-BSS layer 3 protocol . The following Location Services related messages are exchanged between the SMLC and the BSS, with the VMSC acting as a relay.

On the A interface the messages are contained in the Location Information IE which is encapsulated in the BSSMAP-LE Connection Oriented Information message as specified in 3GPP TS 08.08. On the Ls interface the messages are contained in the Location Information IE which is encapsulated in the BSSMAP-LE Connection Oriented Information message as specified in 3GPP TS 09.31.

The following messages types are available:

Message	Encoding
Reserved	00000000
TA Request	00000001
TA Response	00000010
TOA Request	00000100
TOA Response	00000101
Reject	00001010
Reset	00001011
Abort	00001100
TA LAYER3	00001101
MS Position Command	00001111
MS Position Response	00010000

BSSAP

The MTP and the SCCP are used to support signalling messages between the Mobile Services Switching Center (MSC) and the Base Station System (BSS). One user function of the SCCP, called BSS Application Part (BSSAP) is defined. In the case of point-to-point calls the BSSAP uses one signalling connection per active mobile station having one or more active transactions for the transfer of layer 3 messages. In the case of a voice group or broadcast call there is always one connection per cell involved in the call and one additional connection per BSS for the transmission of layer 3 messages. There is an additional connection for the speaker in a broadcast call or the first speaker in a voice group call up to the point at which the network decides to transfer them to a common channel. Additional connections may also be required for any mobile stations in the voice group or broadcast call which the network decides to place on a dedicated connection. The BSSAP user function is further subdivided into two separate functions:

The Direct Transfer Application sub-Part (DTAP), also called GSM L3, is used to transfer messages between the MSC and the MS (Mobile Station); the layer-3 information in these messages is not interpreted by the BSS. The descriptions of the layer 3 protocols for the MS-MSC information exchange are contained in the 04- series of GSM Technical Specifications. The BSS Management Application sub-Part (BSSMAP) supports other procedures between the MSC and the BSS related to the MS (resource management, handover control), or to a cell within the BSS, or to the whole BSS. The description of the layer 3 protocol for the BSSMAP information exchange is contained in Recommendation GSM 08.08. Both connectionless and connection-oriented procedures are used to support the BSSMAP. Rec. GSM 08.08 explains whether connection oriented or connectionless services should be used for each layer 3 procedure. Connection oriented procedures are used to support the DTAP. A distribution function located in BSSAP, which is reflected in the protocol specification by the layer 3 header, performs the discrimination between the data related to those two subparts.

Discrimination Distribution between the two sub-protocols: BSSMAP and DTAP.

DLCI

Only for DTAP. Used in MSC to BSS messages to indicate the type of origination data link connection over the radio interface.

Length Subsequent Layer3 message parameter length.

BSSAPLE

BSSAP-LE is an extension to BSSAP that contains messages and parameters specific to the support of LCS. The BSSAP-LE is part of the LB interface. The following subsets of BSSAP-LE are defined: DTAP-LE and BSSMAP-LE. DTAP-LE messages are transferred between an SMLC and a Type A LMU. BSSMAP-LE messages are transferred between a BSC, MSC and SMLC.

The following BSSMAP-LE message types are available:

Code	Message
0X2B	Perform Location Request
0X2D	Perform Location Response
0X2E	Perform Location Abort
0X1	LMU Connection Request
0X2	LMU Connection Accept
0X3	LMU Connection Reject
0X4	LMU Connection Release
0X2A	Connection Oriented Information
0X3A	Connectionless Information
0X30	Reset
0X31	Reset Acknowledge

BSSMAP

The BSS Management Application Part (BSSMAP) supports all of the procedures between the MSC and the BSS that require interpretation and processing of information related to single calls, and resource management. Some of the BSSMAP procedures result in, or are triggered by, Radio Resource (RR) management messages defined in GSM 04.08.

Message Type A one octet field defining the message type. This mandatory field uniquely defines the function and format of each BSSMAP message.

Information Element Each IE has an identifier which is coded as a single octet. The length of an IE may be fixed or variable and may or may not include a length indicator.

BTSM

BTSM is the Base Station Controller to Base Transceiver Station (BSC - BTS) interface protocol (the A-bis interface). BTSM allows sending messages between the Base Station Controller and the Base Transceiver Station. Protocol messages consist of a series of information elements. For each message there are mandatory information elements and optional information elements. BTSM messages are transmitted on the A-bis interface using the I format of LAPD, except for the Measurement Result message which is sent in UI format.

Message discriminator 1-octet field used in all messages to discriminate between Transparent and Non-Transparent messages and also between Radio Link Layer Management, Dedicated Channel Management, Common Channel Management and TRX Management messages.

Message type Uniquely identifies the function of the message being sent. It is a single octet field.

CC

The call control (CC) protocol is one of the protocols of the Connection Management (CM) sublayer. Every mobile station must support the call control protocol. If a mobile station does not support any bearer capability at all then it must respond to a SETUP message with a RELEASE COMPLETE message. In the call control protocol, more than one CC entity are defined. Each CC entity is independent from each other and communicates with the correspondent peer entity using its own MM connection. Different CC entities use different transaction identifiers.

Certain sequences of actions of the two peer entities compose elementary procedures. These elementary procedures may be grouped into the following classes:

• Call establishment procedures.
• Call clearing procedures.
• Call information phase procedures.
• Miscellaneous procedures.

The terms "mobile originating" or "mobile originated" (MO) are used to describe a call initiated by the mobile station. The terms "mobile terminating" or "mobile terminated" (MT) are used to describe a call initiated by the network.

Protocol discriminator

0011 identifies the CC protocol.

TI flag

Identifies who allocated the TI value for this transaction. The purpose of the TI flag is to resolve simultaneous attempts to allocate the same TI value.

TI value

TI values are assigned by the side of the interface initiating a transaction. At the beginning of a transaction, a free TI value is chosen and assigned to this transaction. It then remains fixed for the lifetime of the transaction. After a transaction ends, the associated TI value is free and may be reassigned to a later transaction. Two identical transaction identifier values may be used when each value pertains to a transaction originated at opposite ends of the interface.

Message type

CC message types may be as follows. Bit 8 is reserved for possible future use as an extension bit. Bit 7 is reserved for the send sequence number in messages sent from the mobile station.

0x000000	Escape to nationally specific message types
0x00	Call establishment messages:
0001	ALERTING
1000	CALL CONFIRMED
0010	CALL PROCEEDING
0111	CONNECT
1111	CONNECT ACKNOWLEDGE
1110	EMERGENCY SETUP
0011	PROGRESS
0101	SETUP
0x01	Call information phase messages:
0111	MODIFY
1111	MODIFY COMPLETE
0011	MODIFY REJECT
0000	USER INFORMATION
1000	HOLD
1001	HOLD ACKNOWLEDGE
1010	HOLD REJECT
1100	RETRIEVE
1101	RETRIEVE ACKNOWLEDGE
1110	RETRIEVE REJECT
0x10	Call clearing messages:
0101	DISCONNECT
1101	RELEASE
1010	RELEASE COMPLETE
0x11	Miscellaneous messages:
1001	CONGESTION CONTROL
1110	NOTIFY
1101	STATUS
0100	STATUS ENQUIRY
0101	START DTMF
0001	STOP DTMF
0010	STOP DTMF ACKNOWLEDGE
0110	START DTMF ACKNOWLEDGE
0111	START DTMF REJECT
1010	FACILITY

DTAP (CDMA)

The Direct Transfer Application Part (DTAP) messages are used to transfer call processing and mobility management messages to and from the MS. The BS does not use DTAP messages, but must map messages going to and coming from the MSC into the appropriate air interface signaling protocol. Transaction IDs are used to associate the DTAP messages with a particular MS and the current call. The format of the header is shown in the following illustration:

TI flag

Identifies who allocated the TI value for this transaction. The purpose of the TI flag is to resolve simultaneous attempts to allocate the same TI value.

TI value

TI values are assigned by the side of the interface initiating a transaction. At the beginning of a transaction, a free TI value is chosen and assigned to this transaction. It then remains fixed for the lifetime of the transaction. After a transaction ends, the associated TI value is free and may be reassigned to a later transaction. Two identical transaction identifier values may be used when each value pertains to a transaction originated at opposite ends of the interface.

Message Type

The message type defines the function of each DTAP message.

Information elements

Each information element has a name which is coded as a single octet. The length of an information element may be fixed or variable and a length indicator for each one may be included.

DTAP (GSM)

The Direct Transfer Application Part (DTAP) are used to transfer call control and mobility management messages between the MSC and the MS. The DTAP information in these messages is not interpreted by the BSS. Messages received from the MS are identified as DTAP by the Protocol Discriminator Information Element. The majority of radio interface messages are transferred across the BSS MSC interface by DTAP, except for messages belonging to the Radio Resource (RR) management protocol.

The DTAP function is in charge of transferring layer 3 messages from the MS (or from the MSC) to the MSC (or to the MS) without any analysis of the message contents. The interworking between the layer 2 protocol on the radio side and signalling system 7 at the landside is based on the use of individual SCCP connections for each MS and on the distribution function.

Protocol discriminator

Identifies the L3 protocol to which the standard layer 3 message belongs. Values may be as follows:

0000	Group call control
0001	Broadcast call control
0010	PDSS1
0011	Call control; call related SS messages
0100	PDSS2
0101	Mobility Management Messages
0110	Radio resources management messages
1001	SMS messages
1011	Non-call related SS messages
1110	Extension of the PD to one octet length
1111	Tests procedures described in TS GSM 11.10

Transaction ID / Skip identifier

Either a transaction identifier, or a skip indicator depending on the level 3 protocol. The transaction identifier contains the transaction value and flag which identifies who allocated the TI.

N(SD)

For MM and CM, N(SD) is set to the value of the send state variable. In other level 3 messages, bit 7 is set to 0 by the sending side. Messages received with bit 7 set to 1 are ignored.

Message type

Uniquely defines the function and format of each GSM L3 message. The message type is mandatory for all messages. The meaning of the message type is therefore dependent on the protocol (the same value may have different meanings in different protocols) and direction (the same value may have different meanings in the same protocol, when sent from the Mobile Station to the network and when sent from the network to the Mobile Station).

Information elements

The message type may be followed by various information elements depending on the protocol.

MM

The main function of the Mobility Management (MM) sub-layer is to support the mobility of user terminals, such as informing the network of its present location and providing user identity confidentiality. A further function of the MM sub-layer is to provide connection management services to the different entities of the upper Connection Management (CM) sub-layer

Protocol discriminator

0101 identifies the MM protocol.

Message type

MM message types may be as follows. Bit 8 is reserved for possible future use as an extension bit. Bit 7 is reserved for the send sequence number in messages sent from the mobile station.

0x00		Registration messages:
	0001	IMSI DETACH INDICATION
	0010	LOCATION UPDATING ACCEPT
	0100	LOCATION UPDATING REJECT
	1000	LOCATION UPDATING REQUEST
0x01		Security messages:
	0001	AUTHENTICATION REJECT
	0010	AUTHENTICATION REQUEST
	0100	AUTHENTICATION RESPONSE
	1000	IDENTITY REQUEST
	1001	IDENTITY RESPONSE
	1010	TMSI REALLOCATION COMMAND
	1011	TMSI REALLOCATION COMPLETE
0x10		Connection management messages:
	0001	CM SERVICE ACCEPT
	0010	CM SERVICE REJECT
	0011	CM SERVICE ABORT
	0100	CM SERVICE REQUEST
	1000	CM REESTABLISHMENT REQUEST
	1001	ABORT
0x11		Miscellaneous messages:
	0001	MM STATUS

MMS

The WAP Multimedia Messaging Service (MMS) uses WAP WSP/HTTP as underlying protocols to transfer MMS PDUs between the MMS Client, which resides on the terminal (MS) and the MMS Proxy -Relay.

This structure is based on the well-known message structure of Internet email binary encoding of MMS PDUs. Because of the limited bandwidth of the air interface of mobile networks MMS PDUs are transferred between an MMS Client and an MMS Proxy -Relay in binary encoded message format. This process is called encapsulation. WSP PDUs or HTTP messages, which contain MMS PDUs as their body, are used for this transport.

MMS PDUs, which are described in this specification, are included in WSP PDUs/HTTP messages of different types. The entire MMS information is contained in MMS PDUs, which are encapsulated in WSP PDUs/HTTP messages.

The content type of WSP PDUs/HTTP messages containing MMS PDUs is "application/vnd.wap.mms - message."

MMS has no header structure as it consists of messages.

Field	Reference Number:
0x81	Bcc
0x82	Cc
0x83	X-Mms-Content-Location
0x84	Content-Type
0x85	Date
0x86	X-Mms-Delivery-Report
0x87	X-Mms-Delivery-Time
0x88	X-Mms-Expiry
0x89	From
0x8A	X-mms-Message-Class
0x8B	Message-ID
0x8C	X-Mms-Message-Type
0x8D	X-Mms-MMS-Version
0x8E	X-Mms-Message-Size
0x8F	X-Mms-Priority
0x90	X-Mms-Read-Report
0x91	X-Mms-Report-Allowed
0x92	X-Mms-Response-Status
0x93	X-Mms-Response-Text
0x94	X-Mms-Sender-Visibility
0x95	X-Mms-Status
0x96	Subject
0x97	To
0x98	X-Mms-Transaction-Id
0x99	X-Mms-Retrieve-Status
0x9A	X-Mms-Retrieve-Text
0x9B	X-Mms-Read-Status
0x9C	X-Mms-Reply-Charging
0x9D	X-Mms-Reply-Charging-Deadline
0x9E	X-Mms-Reply-Charging-ID
0x9F	X-Mms-Reply-Charging-Size
0xA0	X-Mms-Previously-Sent-By
0xA1	X-Mms-Previously-Sent-Date

Message Type

The following message types are contained in the PDU:

128	m-send-req
129	m-send-conf
130	m-notification-ind
131	m-notifyresp-ind
132	m-retrieve-conf
133	m-acknowledge-ind
134	m-delivery-ind
135	m-read-rec-ind
136	m-read-orig-ind
137	m-forward-req
138	m-forward-conf

RR

RR (Radio Resource) management procedures include the functions related to the management of the common transmission resources, e.g., the physical channels and the data link connections on control channels. The general purpose of Radio Resource procedures is to establish, maintain and release RR connections that allow a point-to-point dialogue between the network and a Mobile Station. This includes the cell selection/reselection and the handover procedures. Moreover, Radio Resource management procedures include the reception of the uni-directional BCCH and CCCH when no RR connection is established. This permits automatic cell selection/reselection.

Protocol discriminator

0110 identifies the RR Management protocol.

Skip identifier

Value of 0000.

Message type

Uniquely defines the function and format of each RR message. The message type is mandatory for all messages. RR message types may be:

00111- - -	Channel establishment messages:
011	ADDITIONAL ASSIGNMENT
111	IMMEDIATE ASSIGNMENT
001	IMMEDIATE ASSIGNMENT EXTENDED
010	IMMEDIATE ASSIGNMENT REJECT
00110- - -	Ciphering messages:
101	CIPHERING MODE COMMAND
010	CIPHERING MODE COMPLETE
00101- - -	Handover messages:
110	ASSIGNMENT COMMAND
001	ASSIGNMENT COMPLETE
111	ASSIGNMENT FAILURE
011	HANDOVER COMMAND
100	HANDOVER COMPLETE
000	HANDOVER FAILURE
101	PHYSICAL INFORMATION
00001- - -	Channel release messages:
101	CHANNEL RELEASE
010	PARTIAL RELEASE
111	PARTIAL RELEASE COMPLETE
00100- - -	Paging messages:
001	PAGING REQUEST TYPE 1
010	PAGING REQUEST TYPE 2
100	PAGING REQUEST TYPE 3
111	PAGING RESPONSE
00011- - -	System information messages:
000	SYSTEM INFORMATION TYPE 8
001	SYSTEM INFORMATION TYPE 1
010	SYSTEM INFORMATION TYPE 2
011	SYSTEM INFORMATION TYPE 3
100	SYSTEM INFORMATION TYPE 4
101	SYSTEM INFORMATION TYPE 5
110	SYSTEM INFORMATION TYPE 6
111	SYSTEM INFORMATION TYPE 7
00000- - -	System information messages:
010	SYSTEM INFORMATION TYPE 2bis
011	SYSTEM INFORMATION TYPE 2ter
101	SYSTEM INFORMATION TYPE 5bis
110	SYSTEM INFORMATION TYPE 5ter
00010- - -	Miscellaneous messages:
000	CHANNEL MODE MODIFY
010	RR STATUS
111	CHANNEL MODE MODIFY ACKNOWLEDGE
100	FREQUENCY REDEFINITION
101	MEASUREMENT REPORT
110	CLASSMARK CHANGE
011	CLASSMARK ENQUIRY

See also

• GSM
• Code division multiple access