The protocols described here are from different cellular data communication protocols.
Contents
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:
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:
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:
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.
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:
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.
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.
Message Type
The following message types are contained in the PDU:
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: