3GPP2 A.S0003Version 1.0.0Date: March 16, 2000Abis interface Technical Specification for cdma2000Spread Spectrum Systems(A.S0003 : BSC to BTS Interoperability specification(Abis))COPYRIGHT 3GPP2 and its Organizational Partners claim copyright in this document and individual Organizational Partners may copyright and issue documents or standards publications in individual Organizational Partner's name based on this document. Requests for reproductio n of this document should be directed to the 3GPP2 Secretariat at [email protected]. Requests to reproduce individual Organizational Partner's documents should be directed to that Organizational Partner. See www.3gpp2.org for more information.
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Abis interface Technical Specification for cdma2000 Spread Spectrum Systems
(A.S0003 : BSC to BTS Interoperability specification (Abis))
COPYRIGHT3GPP2 and its Organizational Partners claim copyright in this document and individualOrganizational Partners may copyright and issue documents or standards publications inindividual Organizational Partner's name based on this document. Requests for reproductionof this document should be directed to the 3GPP2 Secretariat at [email protected] to reproduce individual Organizational Partner's documents should be directed tothat Organizational Partner. See www.3gpp2.org for more information.
2.1 S COPE OF THE DOCUMENT ..................................................................................................................................43
4. NETWORK REFERENCE MODEL AND INTERFACES .......................................................................... 76
4.1 S UPPORT OF USER TRAFFIC CONNECTIONS TO A FRAME SELECTOR FUNCTION .........................................1074.2 S UPPORT OF PAGING CHANNEL MESSAGING ...................................................................................................1084.3 S UPPORT OF ACCESS CHANNEL MESSAGING ..................................................................................................1194.4 S UPPORT OF RADIO FUNCTIONS .......................................................................................................................11104.5 S UPPORT OF BROADCAST SYSTEM INFORMATION FUNCTIONS .....................................................................11114.6 LAYERS 1 & 2 ....................................................................................................................................................1212
4.6.1 Physical Layer Specification (Layer 1)..............................................................................................12134.6.2 Use of ATM (Layer 2) ............................................................................................................................12144.6.3 Field of Application ...............................................................................................................................12154.6.4 ATM Layer...............................................................................................................................................12164.6.5 ATM Adaptation Layer..........................................................................................................................12174.6.6 Network and Transport Protocols .......................................................................................................1418
4.6.6.1 Signaling Connection Transport Protocol Options...........................................................................14194.6.6.2 User Traffic Connection Transport Protocol Options.......................................................................15204.6.6.3 TCP Transport Protocol Usage..........................................................................................................15214.6.6.4 General Use of TCP..........................................................................................................................15224.6.6.5 Use of TCP for the Abis Interface.....................................................................................................1723
4.6.7 IP Network Protocol Usage..................................................................................................................17 24
5.1 M OBILE ORIGINATING CALL ...........................................................................................................................19265.2 M OBILE TERMINATED CALL ............................................................................................................................22275.3 C ALL CLEARING ................................................................................................................................................2728
5.3.1 Call Clearing initiated by MS ..............................................................................................................27 295.3.2 Call Clearing initiated by BS/MSC.....................................................................................................29305.3.3 Call Clearing initiated by BTS...............................................................................................................3031
5.4 H ANDOFF ............................................................................................................................................................3232
5.5 SMS D ELIVERY .................................................................................................................................................35355.5.1 SMS Delivery on the Paging channel .................................................................................................35365.5.2 SMS Delivery on the Access channel..................................................................................................36 375.5.3 SMS Delivery on the Traffic channel to MS.......................................................................................37 385.5.4 SMS Delivery on the Traffic channel from MS..................................................................................3839
7. INFORMATION ELEMENT DEFINITIONS ...............................................................................................8529
7.1 I NFORMATION ELEMENT IDENTIFIERS ............................................................................................................85307.2 M ESSAGE TYPE..................................................................................................................................................86317.3 C ORRELATION ID..............................................................................................................................................87327.4 M OBILE IDENTITY .............................................................................................................................................87337.5 C ELL IDENTIFIER ...............................................................................................................................................88347.6 A IR INTERFACE M ESSAGE ................................................................................................................................88357.7 M ANUFACTURER ’S SPECIFIC RECORDS .........................................................................................................88367.8 LAYER 2 A CK REQUEST /RESULTS ...................................................................................................................88377.9 C AUSE .................................................................................................................................................................88387.10 C ALL CONNECTION REFERENCE .....................................................................................................................89397.11 B AND CLASS ......................................................................................................................................................89407.12 P RIVACY INFO ....................................................................................................................................................8941
7.13 C ELL IDENTIFIER LIST ......................................................................................................................................8917.14 SDU-ID ..............................................................................................................................................................8927.15 P HYSICAL CHANNEL INFO................................................................................................................................893
7.16 A BIS CELL INFO.................................................................................................................................................894 7.17 S ERVICE OPTION ................................................................................................................................................8957.18 PACA T IMESTAMP ............................................................................................................................................8967.19 Q UALITY OF SERVICE PARAMETERS ...............................................................................................................9077.20 A BIS CONNECT INFORMATION ........................................................................................................................9087.21 A BIS FROM ID ...................................................................................................................................................9097.22 A BIS TO ID.........................................................................................................................................................90107.23 D OWNLINK RADIO ENVIROMENT ...................................................................................................................91117.24 CDMA S ERVING ONE WAY DELAY ................................................................................................................91127.25 F ORWARD BURST RADIO INFO .........................................................................................................................91137.26 R EVERSE BURST RADIO INFO..........................................................................................................................9114
7.27 IS-2000 F ORWARD POWER CONTROL M ODE ................................................................................................91157.28 IS-2000 FPC G AIN RATIO INFO ......................................................................................................................92167.29 C ELL IDENTIFIER LIST ......................................................................................................................................9217
This document specifies the Abis (between the BSC and the BTS) interface for cdma20003system. Abis interface is the reference point between the BSC and the BTS. The signaling4flows and these signals are described.5
6
2. Objectives7
The Abis interface specification achieves providing an open and interoperable system.8
And Abis interface does not dis turb the coexistence with other A sub -interfaces specified in93GPP2 A.S000110
2.1 Scope of the document11
This specification defines the interface between BTS and BSC within the BS. The12interface between BSs is specified in the 3GPP2 A.S0001 “3GPP2 Access Network 13Interfaces Interoperability Specification (January 18 th , 2000)”.14
The OAM&P related information can be transferred on this interface and the transport15layer for these information are desirable to match with Abis interface. They are for further16study and this specification does not contain them..17
18
3. Glossary19
20
3.1 Glossary21
The following is a list of acronyms that are used in this specification.223G-IOS Third Generation InterOperability Specification23AWIM Alert With Information Message24BS Base Station25BSC Base Station Controller26BTS Base Tranceiver System27ECAM Enhanced Channel Assignment Message28GPM General Page Message29ITU International Telecommunications Union30MAC Medium Access Control31MS Mobile Station32MSC Mobile Switching Center33ORM Origination Message34
PRM Page Response Message1QoS Quality of Service2RAN Radio Access Network 3
RN Radio Network 4 RRC Radio Resource Control Function5SCCM Service Connect Completion Message6SCM Service Connect Message7SDU Selection/Distribution Unit function8
a) Abis interface = Abis signaling + Abis traffic14
15b) An SDU function is located in a BSC16c) A channel element is located in a BTS17
18Notes : The handoff procedure between BTSs within a BSC is defined in this document. The handoff 19procedure s between the BSs have already defined in 3GPP2 A.S0001.20
21
Fig.4-1. Network Reference Model for Abis interface22
4.1 Support of user traffic connections to a frame selector function4
In a CDMA system, the user traffic (voice, data, etc.) of a Mobile Station may be connected5
to the network using one or more connections from MS to BTS(s). If multiple connections6are used for a single flow of user information, the user traffic connection is s aid to be in soft7handoff. The first step within the network is to carry these multiple connections back to a8single point from which a selection is made of the “b es t” frame received over the radio9connections. This implies a connection from each involved BTS back to a central point10where frame selection occurs. This central point is referred to as the “SDU function.”11
1213
4.2 Support of paging channel messaging14
When a BS sends a message on a paging channel, the BSC typically formats the majority of 15the message and then forwards it to the BTS along with various parameters including the16destined cell identifier The ability to forward such a paging message from the BSC to t he17BTS is part of the functionality of the Abis interface.18
An additional requirement of a CDMA system is that such messages may also need to be19forwarded between BSCs to be transmitted to a BTS belonging to a BSC other than the20BSC that originally created the message. This requirement comes through support for21access handoff and other such cdmaOne and cdma2000 features. The BSC to BSC22
signaling on the A7 interface to suppor t such forwarding has been defined in the 3G-IOS1specification.2
4.3 Support of Access channel messaging3
When an MS sends a message on an access channel, the BTS will forward that message to4the BSC along with various parameters including the identity of the cell and sector on5which the message was received, etc. The ability to forward such an access message from6BTS to the BSC is part of the functionality of the Abis interface.7
An additional requirement of a CDMA system is that such a message may also need to be8forwarded between BSCs (i.e., to a BSC other than the one which owns the BTS that9originally received the message). This requirement comes through support for access10handoff and other such cdmaOne and cdma2000 features. The BSC to BSC signaling on11the A7 interface to support such forwarding has been defined in the 3G-IOS specification .12
13
4.4 Support of radio functions14
Various functions can be considered with respect to the radios that exist under the control15of a BTS.16
The interaction of these functions with Operations, Administration, Maintenance, and17Provisioning (OAM&P) are for further study.18
19
4.5 Support of broadcast system information functions20
In a cdmaOne or a cdma2000 system, each BTS must broadcast various pieces of system21information that the MS will capture and use during its in teractions with the network. Much22of that system information may be administrated through OAM&P functions. A small23amount of such system information may be placed in BTS and OAM&P control of a BTS24for the same purposes must be defined.25
26
27
4.6 Layers 1 & 228
29
4.6.1 Physical Layer Specification (Layer 1)30
The Abis interface is based on the use of:31• T1 digital transmission system interfaces. Each 1.544 Mbits/s interface32
provides24*56 kbits/s or 24*64 kbits/s channels which can be used for traffic or1signaling as the operator requires. Common physical interface standards are found in2ANSI T1.101 and related references.3
•
E1 digital transmission interfaces consisting of 30*64 kbits/s user channels can also4be used for traffic or signaling as the operator requires, and as applicable to the5network. 6
• As a BS/MSC agreed option, dedicated DS0 signaling link[s] may be used instead of 7the T1/E1 interface.8
• T3 digital transmission interfaces supporting transmission rates of 43.232 Mbits/sec.9• OC3 digital transmission interfaces supporting transmission rates of 155.5210
Mbits/sec.11
4.6.2 Use of ATM (Layer 2)12
Asynchronous Transfer Mode (ATM) is a suite of protocols that allow fast, efficient13
delivery of user traffic in a packet environment. ATM, for the purposes of this standard,14 consists of two main layers: the ATM Layer that uses the physical layer, and the ATM15Adaptation Layer that adapts the basic ATM layer to specific uses.16
4.6.3 Field of Application17
Asynchronous Transfer Mode (ATM) is used to transport both signaling and user traffic18(voice/data).19
4.6.4 ATM Layer20
The ATM Layer uses a basic 53 octet cell consisting of a 5 octet header and 48 octet21payload. This standard uses the ATM Layer as specified in ANSI T1.627-199322Telecommunications Broadband ISDN - ATM Layer Functionality and Specification 23without modification.24
For this specification only ATM permanent virtual circuits (PVC’s) shall be required for25the Abis interface. These virtual circuits shall be configured through administrative26procedures and no special signaling interface procedures, e.g., ATM UNI (Q.2931), shall27be required.28
4.6.5 ATM Adaptation Layer29
To make use of the basic cell transfer capability of the ATM Transport Layer in specific30uses, various ATM Adaptation Layers (AALs) have been defined.31
Within this standard, two AALs are used:32
AAL51
- for the transfer of signaling, and33AAL2 2 - for the transfer of user traffic (voice/data) on A3 traffic subchannels.34
1 AAL5 is described in ITU-T I.363.5, B- ISDN ATM Adaptation Layer Specification: Type5 AAL, August 1996 .
Both AAL5 and AAL2 will be used without modification in this standard. The Service1Specific Segmentation and Reassembly (SSSAR) sublayer for AAL2, as specified in ITU-T 2
I.366.1 , is used for segmentation and reassembly of AAL2 SDUs.3
In this version of this standard, the functionality of other sublayers of AAL2 is not4supported. Specifically, Service Specific Transmission Error Detection (SSTED) and5Service Specific Assured Data Transfer (SSADT) are not included.6
7
2 AAL2 is described in ITU-T Recommendation I.363.2, B-ISDN ATM Adaptation Layer Type 2 Specification , September 1997.
4.6.6.1 Signaling Connection Transport Protocol Options3
Signaling over the Abis interface requires a reliable transport protocol and appropriate4addressing and routing mechanisms to deliver messages from source to destination. The5Abis signaling application is independent of the underlying transport, which is left to the6discretion of operators and manufacturers. The signaling protocol stack options available to7operators and manufacturers for the Abis interface include:8
4.6.6.2 User Traffic Connection Transport Protocol Options1
The protocol stack options for transport of user traffic that are available to operators and2
manufacturers include:34
Abis Interface (user traffic subchannel):56
Abis TrafficSSSARAAL2ATM
Phys. Layer7
4.6.6.3 TCP Transport Protocol Usage8
The standard TCP protocol, as described in reference 3, IOS section 1.5.4, shall be used for9establishing, using, and clearing TCP connections.10
4.6.6.4 General Use of TCP11
TCP connections for signaling may be set up on a per-call basis or signaling messages for12multiple calls may be multiplexed on a single TCP connection.13
The TCP protocol provides a reliable byte stream transfer. Therefore, a means needs to be14provided for two application entities to delimit the messages sent between them. The15technique for such delimitation is given below.16
4.6.6.4.1 Message Delimiting in TCP17
TCP provides a reliable byte stream between two application entities. Because the protocol18in this standard uses messages to communicate, these messages shall be delimited in the19TCP byte stream. Such delimitation shall be done by means of a two byte flag field and a20two byte length field inserted at the beginning of each message sent over a TCP connection.21The flag field shall contain the hex value “F634”. The purpose of the flag field is to22facilitate verification of message boundaries, and fast reestablishment of synchronization if 23synchronization of message boundaries is lost. See Figure 4-3 below.24
A new TCP connection is established when a signaling message re lated to a call has to be2exchanged over an interface, and no such connection exists over the particular interface.3
Normal TCP connection establishment procedures are used.4
4.6.6.4.3 TCP Connection Release5
An existing TCP connection over an interface is released when there are no more signaling6messages to be exchanged over the interface. Normal TCP connection release procedures7are used.8
4.6.6.4.4 TCP Port Usage9
The following TCP port values are reserved for signaling across A bis interfaces:10
Abis: 5604 -- This is the well-known TCP port at a BS used for Abis signaling11interconnection between BTSs and a BSC .12
13
Editor’s Note : These port number is requested now. The value may be changed. And the14value will be defined in A.S0001 later version.15
16
A7: (BS-to-BS) 5602 -- This is the well-known TCP port at a BS used for signaling17interconnection to another BS.18
A9: (BS-to-PCF) 5603 -- This is the well-known TCP/UDP port at a BS used for signaling19interconnection to a PCF.20
4.6.6.5 Use of TCP for the Abis Interface21
The standard " Transport Control Protocol (TCP)", as described in RFC793 and shown in22IOS section 5.4.1 shall be used on the A3 (signaling subchannel) and A7 interfaces.23
4.6.7 IP Network Protocol Usage24
The standard IP protocol, as defined in RFC 791 (see IOS section 1.5.4), shall be used for25routing Internet Protocol packets.26
a. The MS transmits an Origination Message, with layer 2 acknowledgement required, over1the access channel of the air interface to the BTS. Then the BTS sends an Abis -ACH2Msg Transfer including the Origination message frame in Abis signaling interface.3
b. The BSC constructs the CM Service Request message, places it in the Complete Layer 34Information message, sends the message to the MSC, and star ts timer T303. The BSC5may request the MSC to allocate a preferred terrestrial circuit.6
c. The MSC sends an Assignment Request message to the BSC to request assignment of 7radio resources. This message will include information on the terrestrial circuit, if one is8to be used between the MSC and the BSC. The MSC then starts timer T10.9
d. The BSC sends Abis -BTS Setup message to get the resource between BSC and BTS.10The BSC shall allocate a code channel and include it in the Abis -BTS Setup.11
e. If resources are available, BTS responses with Abis -Connect message.12
f. The BSC sends Abis -Connect Ack message to the BTS.13
g. The BTS sends Abis -BTS Setup Ack to the BSC to acknowledge the Abis-BTS Setup.14
The BTS may allocate a code channel. In this case, the BTS includes the allocated code15 channel in Abis-BTS Setup Ack. Unless the BTS allocates a code channel, the BTS16includes the code channel that has been indicated by Abis -BTS Setup (step d) in the17Abis-BTS Setup Ack.18
h. The BSC transmits the Abis -IS-2000 FCH Fwd message to the BTS including Null Data19to let the BTS send Null traffic data toward the MS. Then the BTS begin sending Null20Traffic data for synchronizing between the BTS and the MS. The BTS may have function21which sends Null Traffic data for synchronization between the BTS and the MS.22Whether the BTS has the function or not, the BSC is assumed to send Null Traffic.23
i. The BTS sends Abis -IS-2000 FCH Rvs message to the BSC including Idle data.24
j. The BSC sends an Abis -PCH Msg Transfer including Extended Channel Assignment25message to the BTS. The BTS sends an Extended Channel Assignment message to the26
MS over the paging channel of the radio interface (with the MS address) to initiate the27establishment of a radio traffic channel.28
k. The MS begins sending the traffic channel preamble (TCH Preamble) over the29designated reverse traffic channel. Then the BTS transmits this preamble with an30Abis-IS-2000 FCH Rvs message.31
l. Once the BSC acquires the reverse traffic channel, it sends an Abis -IS-2000 FCH Fwd32message including a Base Station Acknowledgement Order with layer 233acknowledgement required, to the MS over the forward traffic channel.34
m. After receiving a BS Ack Order message, the MS begins sending Idle Tch Data Frames35over the reverse traffic channel. Then the BTS transmits this frame message with an36Abis-IS-2000 FCH Rvs message.37
n. The MS Ack Order message is sent from MS, and then the BTS transmits it to the BSC38 with an Abis-IS-2000 FCH Rvs message.39
o. The BSC then sends the Abis -IS-2000 FCH Fwd message including the Service Connect40message to the BTS specifying the service configuration for the call. Then the BTS41transmits the Service Connect message to the MS. The MS begins processing traffic in42accordance with the specified service configuration.43
p. On receipt of the Service Connect message, the MS responds with a Service Connect1Completion message. Then the BTS transmits i t with an Abis -IS-2000 FCH Rvs2message.3
q. After the radio traffic channel and circuit have both been established and fully4interconnected, the BSC sends the Assignment Complete message to the MSC and5considers the call to be in conversation state.6
The MSC stops timer T10 upon receipt of the Assignment Complete message.789
This section describes the call flow associated with a mobile station call termination in the2 cdma2000 system. An Abis -PCH Msg Transfer Ack and an Abis -ACH Msg Transfer Ack are3not presented in the following figure to simplify the figure, but actually, they would be sent4after receipt of Abis -PCH Msg Transfer message or Abis -ACH Msg Transfer message5respectively.6
a. The MSC sends the Paging Request message to the BSC to initiate a1mobile terminated call setup scenario.2
b. The BSC constructs a General Page Message (GPM), put the message3into an Abis-PCH Msg Transfer Message and sends the Abis-PCH4Msg Transfer Message to the BTS. The BTS sends the GPM to the MS5over the paging channel. The BSC may send this message to multiple6BTSs managed by this BSC. In the following description, it is assumed7that the BSC sends this message to single BTS.8
c. The MS acknowledges the page by transmitting a Page Response9Message (PRM) to the BTS over the access channel. Upon receipt of 10this message, the BTS put this message into an Abis-ACH Msg11Transfer Message and sends it to the BSC.12
d. The BSC sends the Complete Layer 3 Information message containing13the Paging Response message to the MSC.14
e. The BSC acknowledges the receipt of the PRM from the MS with a15Base Station Acknowledgment Order to the MS. This message is sent16by the BSC to the BTS in the Abis-PCH Msg Transfer.17
f. The MSC sends an Assignment Request message to request18assignment of radio resources.19
g. The BSC sends an Abis-BTS Setup message to the BTS to request20allocation of radio resources at the BTS. The BSC shall allocate a code21channel and include it in the Abis-BTS Setup.22
h. Upon receipt of Abis-BTS Setup message, the BTS allocates radio23resources and sends an Abis -Connect message to initiates an Abis24connection and to report the result of resource allocation.25
i. The BSC replies with an Abis-Connect Ack message to complete the26Abis connect ion.27
j. The BTS sends Abis -BTS Setup Ack to acknowledge the Abis -BTS28
Setup. The BTS may allocate a code channel. In this case, the BTS29includes the allocated code channel in the Abis-BTS Setup Ack.30Unless the BTS allocates a code channel, the BTS includes the code31channel that has been indicated by Abis -BTS Setup (step g) in the32Abis-BTS Setup Ack.33
k. The BSC sends an Abis -IS-2000 FCH Fwd (Null Traffic Data)1message to the BTS. The BTS starts sending Null Traffic Data to the2MS. This allows the MS to acquire the FCH (Fundamental channel).3
The BTS may have function which sends Null Traffic data for4 synchronization between the BTS and the MS. Whether the BTS has5the function or not, the BSC is assumed to send Null Traffic. 6
l. Upon receiving the first Abis -IS-2000 FCH Fwd (Null Traffic Data)7message, the BTS starts to send Abis-IS-2000 FCH Rvs (Idle frame)8message to the BSC.9
m. The BSC sends an Extended Channel Assignment message to assign10the FCH.11
n. The MS starts to send the Traffic Channel Preamble. Upon receiving12the Traffic Channel Preamble, the BTS stops sending the idle frames13and starts sending the traffic frames containing the Traffic Channel14Preamble.15
o. The BSC sends the BS Ack Order to the MS via the BTS in the16Abis -IS-2000 FCH Fwd message.17
p. The MS stops transmitting the Traffic Channel Preamble and starts to18transmit idle traffic channel data frames upon receipt of the BS Ack 19order.20
q. The MS sends the MS Ack Order to acknowledge the BS Ack order.21This is sent by the BTS to the BSC in the Abis -IS-2000 FCH Rvs22message.23
r. The BSC sends the Service Connect Message (SCM) to the MS24specifying the service configuration for the call. This message is sent25by the BSC to the BTS in the Abis-IS-2000 FCH Fwd message. The26MS begins processing traffic in accordance with the specified service27configuration.28
s. On receipt of the Service Connect Message (SCM), the MS responds29
with a Service Connect Completion Message (SCCM). Upon receipt30 of this message at the BTS, it sends Abis -IS-2000 FCH Rvs message31containing this message to the BSC.32
t. After the radio traffic channel and circuit have both been established,33the BSC sends the Assignment Complete message to the MSC.34
u. The BSC sends an Alert with Information Message (AWIM) to the MS1to cause ringing at MS. This message is sent by the BSC to BTS in the2Abis -IS-2000 FCH Fwd message.3
v. The MS acknowledges the reception of the Alert with Information4Message by transmitting the MS Ack Order.5
w. When the call is answered at the MS, a Connect Order, with6acknowledgment required, is transmitted to the BSC via the BTS.7
x. The BSC acknowledges the Connect Order with the BS Ack order.8
y. The BSC sends a Connect message to the MSC to indicate that the call9has been answered at the MS. At this point, the call is considered stable10and in the conversation state.11
a. The MS initiates call clearing by transmitting a Release Order over the23reverse traffic channel. In response to the order, BTS sends an24Abis -IS-2000 FCH Rvs message containing the Release Order25message to the BSC.26
b. The BSC then sends the Clear Request message to the MSC to initiate27the call clear transaction. Timer T300 is started by the BSC.28
c. The MSC starts timer T315 and sends a Clear Command message to29the BSC to instruct the BSC to release the associated dedicated30resource (such as terrestrial circuit). The BSC stops timer T300.31
d. In response to the Clear Command message from the MSC, the BSC32sends an Abis -IS-2000 FCH Fwd message containing the Release33
MS BTS MSC
Clear Request
Clear Command
Clear Complete
BSC
BS
Release Order Abis-IS-2000 FCH Rvs (Release Order)
Order message. The BTS then acknowledges the MS by sending it a1Release Order over the forward traffic channel.2
e. The BSC then sends an Abis-BTS Release message to the BTS.3
f. The BTS releases the radio resource and sends Abis-Remove message4to the BSC.5
g. In response to the Abis -Remove message from the BTS, BSC sends an6Abis-Remove Ack message to the BTS.7
h. The BTS sends an Abis -BTS Release Ack message to the BSC to8acknowledge the Abis removal.9
i. The BSC sends a Clear Complete message to the MSC. Then BSC10
releases the related terrestrial circuit to the BTS, if allocated. And the11MSC stops timer T315 upon receipt of the Clear Complete message.12The MSC releases the underlying transport connection.13
a. In the case where the BSC detects some failures related the call, the13BSC sends a Clear Request message to the MSC. The BSC starts timer14T300 and waits for the Clear Command from the MSC (step b). A Call15Clearing flow initiated by BSC starts from this step.16
b. The MSC starts timer T315 and sends a Clear Command message to17instruct the BSC to release the associated dedicated resource (such as18terrestrial circuit). In the case of a Call Clearing initiated BS, the BSC19stops timer T300. A Call Clearing flow initiated by MSC starts from20this step.21
c. In response to the Clear Command message from the MSC, the BSC22sends Abis-IS-2000 FCH Fwd containing the Release Order message.23The BTS sends the Release Order message to the MS over the forward24traffic channel.25
d. The MS replies with a Release Order over the reverse traffic channel.26In response to the order, BTS sends an Abis -IS-2000 FCH Reverse27containing the Release Order message to the BSC.28
MS BTS MSC
Clear Request
Clear Command
BSC
BS
Release Order Abis-IS-2000 FCH Fwd (Release Order)
e. The BSC then sends an Abis-BTS Release message to the BTS.1
f. The BTS releases the radio resource and sends Abis Remove message2to the BSC.3
g. In response to the Abis Remove message from the BTS and BSC sends4an Abis Remove Ack message to the BTS. Then BSC releases the5related terrestrial circuit to the BTS, if allocated.6
h. The BS sends an Abis -BTS Release Ack message to the BSC to7acknowledge the Abis removal8
i. Upon receipt of the Abis BTS Release Ack message, the BSC sends9the Clear Complete message to the MSC. The MSC stops timer T31510upon receipt of the Clear Complete message. The MSC releases the11underlying transport connection.12
5.3.3 Call Clearing initiated by BTS13
14
Fig. 5-5 Call Clearing initiated by BTS15
a. In the case of a radio channel failure between the MS and the BTS, or16if the MS is not active, the BTS sends an Abis -BTS Release Request17
MS BTS MSC
Clear Request
Clear Command
Clear Complete
BSC
BS
Release Order Abis-IS-2000 FCH Fwd (Release Order)
message to BSC. In response to the message the BSC sends a Clear1Request message to the MSC. The BSC starts timer T300 and waits for2the Clear Command from the MSC (step b). A Call Clearing flow3
initiated by BS starts from this step.4
b. The MSC starts timer T315 and sends a Clear Command message to5instruct the BSC to release the associated dedicated resource (such as6terrestrial circuit). The BSC stops timer T300.7
c. In response to the Clear Command message from the MSC, the BSC8sends Abis -IS-2000 FCH Fwd containing the Release Order9message.The BTS sends the Release Order over the forward traffic10channel.11
d. The MS replies with a Release Order over the reverse traffic channel.12In response to the order, BTS sends an Abis-IS-2000 FCH Rvs13containing the Release Order message to the BSC.14
e. The BSC then sends an Abis-BTS Release message to the BTS.15
f. The BTS releases the radio resource and sends Abis-Remove message16to the BSC.17
g. In response to the Abis-Remove message from the BTS and BSC18sends an Abis Remove Ack message to the BTS and returns a Clear19Complete message to the MSC. Then BSC releases the related20
terrestrial circuit to the BTS, if allocated.21
h. The BS sends an Abis -BTS Release Ack message to the BSC to22acknowledge the Abis -removal23
i. Upon receipt of the Abis BTS Release Ack message, the BSC sends24the Clear Complete message to the MSC. The MSC stops timer T31525upon receipt of the Clear Complete message. The MSC releases the26underlying transport connection.27
This section describes handoff procedure using Abis interface within the BS. The handoff 2 between BSs is realized by A3 and A7 interface specified in 3GPP2 A.S0001.3
5.4.1 Soft/Softer Handoff (Intra-BTS)45
Fig.5-6 Soft/Softer Handoff (Intra-BTS)6
7
a. The BSC sends an Abis-BTS Setup message to the BTS to request that the specified8cells be added to the call. The BSC shall allocate a code channel and include it in the9Abis -BTS Setup.10
b. The BTS allocates internal resources related to the specified cells. The BTS sends an11Abis -Connect message to the SDU function.12
c. The SDU function of BSC replies with an Abis-Connect Ack message and allocate13internal resources .14
d. The BTS sends Abis -BTS Setup Ack to acknowledge the Abis -BTS Setup. The BTS15 may allocate a code channel. In this case, the BTS includes the allocated code channel in16
Abis -BTS Setup Ack. Unless the BTS allocates a code channel, the BTS includes the17code channel that has been indicated by Abis-BTS Setup (step a) in the Abis -BTS Setup18Ack.19
e. The BSC sends an Extended / General / Universal Handoff Direction Message to the MS20to add the new cell to the active set .21
Ab Abis -BTS Setup
MS BSC
Extended/General/UniversalHandoff Direction Message
f. The MS acknowledges receipt of the Extended / General / Universal Handoff Direction1Message with an MS Ack Order.2
g. The MS indicates successful results of processing the Extended / General / Universal3Handoff Direction Message by sending a Handoff Completion message.4
h. The BSC acknowledges receipt of the Handoff Completion Message by sending a BS5Ack Order.6
7
5.4.2 Soft/Softer Handoff (Inter-BTS)8
9
Fig.5-7 Soft/Softer Handoff (Inter-BTS)10
a. The BSC decides that one or more cells at the target BTS are needed to support the call11in soft/softer handoff. The BSC sends an Abis-BTS Setup to the target BTS to get the12resource between BSC and the target BTS. The BSC shall allocate a code channel and13include it in the Abis-BTS Setup.14
b. If resources are available, The target BTS responses with Abis -Connect message.15
c. The BSC replies with an Abis-Connect Ack message to complete the Abis connection.16d. The target BTS sends Abis-BTS Setup Ack to acknowledge the Abis -BTS Setup. The17
target BTS may allocate a code channel. In this case, the target BTS includes the18allocated code channel in Abis -BTS Setup Ack. Unless the target BTS allocates a code19channel, the target BTS includes the code channel that has been indicated by Abis -BTS20Setup (step a) in the Abis -BTS Setup Ack.21
e. The BSC begins to send the forward frames to the target BTS.22
Ab Abis -BTS Setup
MS BSCSource
BT S
Extended/General/UniversalHandoff Direction Message
f. The target BTS transmits the forward frames to the MS.1
g. The target BTS begins to transmit the forward frames as soon as synchronization has2occurred and to send reverse idle frames . The reverse frames contain the timing3adjustment information necessary to achieve synchronization.4
h. If the BSC has chosen to be notified of the start of transmission and reception at the5target BTS, when its SDU function and the target BTS have synchronized Abis traffic6subchannel, the BSC send an Abis-Traffic Channel Status message to the source BTS7
i. The BSC sends an Extended / General / Universal Handoff Direction Message to the MS8to add the new cell to the active set.9
j. The MS acknowledges receipt of the Extended / General / Universal Handoff Direction10Message with an MS Ack Order.11
k. The MS indicates successful results of pro cessing the Extended / General / Universal12Handoff Direction Message by sending a Handoff Completion message.13
l. The BSC acknowledges receipt of the Handoff Completion Message by sending a BS14
This section provides the call flow description for the delivery of an SMS from the MSC4to an idle mobile station on the paging channel.5
6
7
Fig. 5-8 SMS Delivery on the Paging channel8
a. When the MSC determines that a point-to-point short message should be sent to an9idle MS, the MSC sends ADDS Page message to the BSC.10
b. The BSC sends the Abis-PCH Msg. Transfer that includes a Data Burst Message.11The Data Burst Message contains the short message in received ADDS Page.12
c. The BTS transfers the Data Burst Message which is included in the Abis -PCH Msg.13Transfer message, on a Paging Channel.14
d. The MS acknowledges the receipt of the Data Burst Message, if it is required.15
e. The BTS sends the Abis -ACH Msg. Transfer message that contains an MS Ack 16 Order Message.17
f. The BSC sends ADDS Page Ack to acknowledge the ADDS Page.18
This section provides the call flow description for the delivery of an SMS from an idle2mobile station to the MSC on the access channel.3
4
Fig. 5-9 SMS Delivery on the Access channel5
6
a. The MS sends a Data Burst Message on the Access Channel to transfer the SMS7message.8
b. The BTS sends the Abis -ACH Msg. Transfer message that includes the Data Burst9
Message received on the Access Channel.10
c. The BSC sends the ADDS Transfer message to the MSC containing the Data Burst11Message received from the MS in the ADDS User Part element.12
d. The BTS sends the Abis -PCH Msg. Transfer message that includes the BS13Acknowledge Order Message to acknowledge the Data Burst Message, if it is14required.15
e. The BTS sends the BS Ack Order included in the Abis -PCH Msg. Transfer message. 16
This section provides the call flow description for the delivery of an SMS from the MSC to2
a mobile station operating on the traffic channel.3
4
Fig. 5-10 SMS Delivery on the Traffic channel to MS5
a. When the MSC determines that a point-to-point short message should be sent to an6MS operating on a traffic channel, the MSC sends ADDS Deliver message to the7BSC.8
b. The BSC sends Abis -IS-2000 FCH Fwd containing the Data Burst Message9
c. The Data Burst Message is sent on the traffic channel.10
d. The MS acknowledges the receipt of the Data Burst Message, if it is required.11
e. The BTS sends Abis -IS-2000 FCH Rvs containing the MS Ack Order.12
f. The BSC sends ADDS Deliver Ack to acknowledge the ADDS Deliver.13
5.6.1 Initial Traffic Burst Example – Abis Connection Not Yet Established3The example below describes the support of traffic burst operation when the Abis connection4has not yet been established.5
M S BTS MSC Time Comment
a
b
c
d
e
f
g
BSC
h
j
i
k
AbAbis -BTS Setup
A3Abis -Connect
A3Abis -Connect Ack
ESCAM
SCRM (data to be sent)
AbAbis -BTS Setup Ack
AbAbis -Burst Request
AbAbis -Burst Response
AbAbis -Burst Commit
Layer 2 Ack
Forward and/or reverse traffic burst
optional
optional
6Fig. 5-12 Initial Traffic Burst Example7
a. Either the BSC receives an indication from the MS (via a SCRM8message) or from the network (via data being received from the9PDSN) that data needs to be sent to/from the MS. The BSC decides a10traffic burst on one or more new cells at a BTS is required in support of 11a service instance in soft/softer handoff. This example assumes that a12Fundamental Channel (FCH) leg already exists on the selected cell(s)13at the BTS.14
b. The BSC assigns an Abis From ID value and sends an Abis BTS Setup15message to the BTS to establish an Abis traffic connection to support a16Supplemental Channel (SCH) for the call. This example shows only a17single Abis connection being established. The BSC is not required to18assign a physical Frame Selector at this time.19
c. The BTS assigns a traffic circuit and optionally a Channel Element ID1(CE ID) for each Abis traffic connection and sends an Abis -Connect2message to the BSC indicating the Traffic Circuit ID, optional Abis3
From ID and CE ID to be associated with the specified Abis From ID.4 The BSC and BTS save the association of CE ID, Traffic Circuit ID,5with Cell ID(s). The BSC also saves the Abis From ID value, to be6included in subsequent Abis messages to the BTS. This is only done at7the initial burst.8
d. The BSC responds with an Abis Connect Ack message to complete the9Abis connection. This includes an Abis From ID value assigned by the10BSC, which will be included by the BTS in subsequent Abis messages11to the BSC.12
e. The BTS sends Abis -BTS Setup Ack messages to the BSC to complete13the Abis traffic circuit connection setup procedure for the specified set14of cells. This includes an Abis From ID value assigned by the BTS,15which will be included by the BSC in subsequent Abis messages to the16BTS for this call association.17
When the BSC has knowledge of resources for SCH in the BTS, the18procedure at step f and at step g is not necessary.19
f. The BSC sends an Abis -Burst Request including the Abis to ID to the20BTS to request the reservation of the needed radio resources for the21supplemental channel. Note that the BSC may send an Abis -Burst22Request to the BTS at any time after receiving the Abis -BTS Setup23message in step c, and that the set of cells may be subset of the cells24assigned in step a-e.25
g. The BTS determines that it can reserve part or all of the requested26resources and sends Abis-Burst Response message(s) including Abis27From ID to the BSC indicating the resources that have been reserved28and committed to the traffic burst, and the cause value for any29uncommitted cells. Each reservation includes a physical Channel30Element. Note that the physical Channel Element may be allocated any31time after step b.32
h. The BSC makes a final decision on the resources to be used for the33traffic burst and sends an Abis -Burst Commit message to each BTS34indicating the set of committed resources that will actually be used for35the traffic burst. Note that the BSC may allocate the frame selector any36time after step b. Any resources (cells) not included in the Abis -Burst37Commit message may be released by the BTS.38
i. The BSC commands the MS to prepare for the traffic burst via an1ESCAM message.2
j. The MS acknowledges the command from the source BS with a Layer32 Ack.4
k. The network and MS exchange forward and/or reverse traffic burst5information for the specified duration, or until the BSC terminates or6extends the traffic burst.7
5.6.2 Subsequent Traffic Burst Example1The example below describes the support of traffic burst operation when the Abis connection2
for the supplemental channel (SCH) has already been established.3
MS BTS MSC Time Comment
a
b
c
d
e
f
g
BSC
ESCAM
SCRM (data to be sent)
AbAbis -Burst Request
AbAbis -Burst Response
AbAbis -Burst Commit
Layer 2 Ack
Forward and/or reverse traffic burst
optional
optional
4
Fig. 5-13 Subsequent Traffic Burst Example5
a. Either the BSC receives an indication from the MS (via a SCRM6message) or from the network (via data being received from the7PDSN) that data needs to be sent to/from the MS.8
When the BSC has knowledge of resources for SCH in the BTS, the9procedure at step b and at step c is not necessary.10
b. The BSC decides a traffic burst is required on one or more cells for11which an Abis connection already exists in support of a supplemental12channel. The BSC sends an Abis-Burst Request to the BTS to request13the reservation of the needed radio resources for the supplemental14channel.15
c. The target BS determines that it can reserve part of all of the requested16resources and sends Abis -Burst Response massage(s) to the BSC17indicating the resources that have been reserved and committed to the18
traffic burst, and the cause value for any uncommitted cells. Each19reservation includes a physical Channel Element. Note that the20physical Channel Element may be allocated any time after step b.21
d. The BSC makes a final decision on the resources to be used for the22traffic burst and sends an Abis -Burst Commit message to each BTS23indicating the set of committed resources that will actually be used for24
the traffic burst. Note that the BSC may allocate the frame selector any1time after step b. Any resources (cells) not included in the Abis -Burst2Commit message may be released by the BTS.3
e. The BSC commands the MS to prepare for the traffic burst via an4ESCAM message.5
f. The MS acknowledges the command from the source BS with a Layer62 Ack.7
g. The network and MS exchange forward and/or reverse traffic burst8information for the specified duration, or until the BSC terminates or9extends the traffic burst.10
11
12
Abis Interface Message Formats13
For Abis Interface message there are a number of information elements that are14individually defined in section 6.1. Each information element in a given message is tagged15with a reference in section 6.1, a direction indication (i.e., some elements within a message16are bi-directional and others are not), and a mandatory/optional type (M/O) indicator.17
The inclusion of information elements in each message is specified as follows:18
? M - information elements which are mandatory for the message.19
? O - information elements which are optional for the message.20
6.1 Abis interface message21
22
6.1.1 Abis-ACH Msg Transfer23
This Abis interface message is sent from the BTS to the BSC to notify the BSC of the24reception of the contained message or Layer 2 acknowledgment on the specified access25channel.26
This Abis interface message is sent from the BSC to the BTS to request the sending of the3contained message on the specified paging channels to a mobile station.4
Information Element SectionReference
Element Direction Type
Message Type 7.2 BSC -> BTS M
Correlation ID 7.3 BSC -> BTSO
a
Mobile Identity (IMSI/MIN) 7.4 BSC -> BTS O
Mobile Identity (ESN) 7.5 BSC -> BTS O
Cell Identifier List 7.13 BSC -> BTSO
b
Air Interface Message 7.6 BSC -> BTS O
Layer 2 Ack Request/Results 7.8 BSC -> BTSO
c
Manufacturer’s Specific Record 7.7 BSC -> BTS O
a. If this element is included in this message, the value shall be returned in the5Abis -PCH Msg Transfer Ack message.6
b. This element indicates the cells at the BTS on whose paging channel(s) the7air-interface message is to be sent.8
c. This element is included if the source BS wants a Layer 2 acknowledgment9
⇒ Manufacturer’s Specific Records : Abis Element Identifier = [70H] 1
Length = [variable] 2
Manufacturer ID = [00H – FFH] 3
Manufacturer’s specific information 4
• • • • • •
n
1
2
3
45
6.1.4 Abis-PCH Msg Transfer Ack6
This Abis interface message is sent from the BTS to the BSC to report the results of 7sending an air interface message on the specified paging when a layer 2 acknowledgment8had been requested by the BSC.9
This Abis interface message is sent from the BSC to the BTS in order to request the BTS to6assign radio resource, the at tributes of which are defined within the message.7
Information Element SectionReference
ElementDirection
Type
Message Type 7.2 BSC -> BTS M
Call Connection Reference 7.10 BSC -> BTS MBand Class 7.11 BSC -> BTS O
Privacy Info 7.12 BSC -> BTS O
SDU-ID 7.14 BSC -> BTS O
Mobile Identity (IMSI/MIN) 7.4 BSC -> BTS O
Mobile Identity (ESN) 7.4 BSC -> BTS O
Physical Channel Info 7.15 BSC -> BTS O
Abis Cell Info 7.16 BSC -> BTS O
Service Option 7.17 BSC -> BTS O
PACA Timestamp 7.18 BSC -> BTS Oa
Quality of Service Parameters 7.19 BSC -> BTS Ob
Abis Connect Information 7.20 BSC -> BTS Oc
Abis From ID 7.21 BSC -> BTS O d
Manufacturer’s Specific Records 7.7 BSC -> BTS O
a. This element may be present only when the call is eligible for PACA service.8
b. This element may be only used for packet data calls. In this version of this9standard, this element is used to carry a Packet Priority field coded on 4 bits.10
Values ‘1110’ and ‘1111’ are reserved.11
c. This element may be used to indicate a code channel that is allocated by the BSC.12It is assumed that the Cell Info Record i s used and the rest of the fie lds are filled by130.14
d. This element is optionally included by the BTS. If included, the value shall be1saved and used by the BSC in subsequent Abis message for this call association.2
Call Connection Reference 7.10 BTS -> BSC MAbis Connect Information 7.20 BTS -> BSC O
Abis From ID 7.21 BTS -> BSC O a
Abis To ID 7.22 BTS -> BSC O b
Manufacturer’s Specific Records 7.7 BTS -> BSC O
a. This element is optionally included by the BTS. If included, the value1shall be saved and used by the BSC in subsequent Abis message for this2call association.3
b. This element is required if an Abis From ID value was included in the4
corresponding Abis -BTS Setup message5
6
77 6 5 4 3 2 1 0 Octet
⇒ Message Type = [81H] 1
⇒ Call Connection Reference: A1 Element Identifier = [3FH] 1
Length = [08H] 2
(MSB) Market ID = <any value> 3
(LSB) 4(MSB) Generating Entity ID = <any value> 5
(LSB) 6
(MSB) 7
Call Connection Reference = <any value> 8
9
(LSB) 10
⇒ Abis Connect Information{1+: A3/A7 Element Identifier = [1BH] 1
Length = <variable> 2
Reserved = [000] Physical Channel Type
= [0H - IS-95 Fundamental Channel,1H – Fundamental Channel (FCH),2H – Supplemental Channel (SCH)],
a. If this element is omitted, the target BS shall send all Abis signaling messages1related to the call to the same address as is used to reply to this A7 message.2
b. Optionally included by the source BS. If included, the value shall be saved and3used by the target BS on Abis signaling messages.4
c. This element may be included for OA&M purposes.5
d. The list of cell identifiers shall be assumed by the target BS to be in priority6order with the highest priority cell listed first.7
e. This element is only included when forward link radio resources are to be8allocated to the burst.9
f. This element is only included when reverse link radio resources are to be10allocated to the burst.11
g. If this element is included in this message, its value shall be returned in the12Abis -Burst Response message and used in the Abis-Burst Commit message.13
h. This element is required if an Abis From ID value was included in an Abis-BTS14Setup Ack message previously received from the BS for this call association.15
This Abis interface message is sent from the BTS to the BSC to respond to a request for3reservation of resources to support a traffic burst. Note that one or more Abis -Burst4Response messages may be used to respond to a single Abis-Burst Request message. A5result (committed or uncommitted) must be provided for all cells in the Abis -Burst Request6message. Each Abis-Burst Response message includes at most one committed cell.7
Cell Identifier List (Uncommitted) 7.13 BTS -> BSCO
e
Forward Burst Radio Info 7.25 BTS -> BSCO
b
Reverse Burst Radio Info 7.26 BTS -> BSCO
c
Abis To ID 7.22 BTS -> BSCO
f
a. If this element was included in the Abis-Burst Request message, the11value shall be returned in this message.12
b. This element is only included when this message includes information13about forward link radio resources that have been reserved at the cell14indicated in the Cell Identifier List (Committed) element.15
c. This element is only included when this message includes information16about reverse link radio resources that have been reserved at the cell17indicated in the Cell Identifier List (Committed) elemen t.18
d. This element is only included when this message includes information19 about a cell with radio resources reserved for the forward and/or20reverse burst indicated in the Forward and/or Reverse Burst Radio Info21element.22
e. This element is only included when this message includes one or more23requested cells that are not being reserved. The allowable cause values24
are: OAM&P intervention, Equipment failure, No radio resource1available, BS not equipped, Ciphering algorithm not supported,2Private Long Code not available or not supported, Requested MUX3
option or rates not available, Requested privacy configuration not4 available.5
f. This element is required if an Abis From ID value was included in an6Abis -BTS Setup message previously received from the BSC for this7call association.8
This Abis interface message is sent from the BSC to the BTS to commit a set of resources3that had been reserved to support a traffic burst.4
Abis567
Information Element SectionReference
Element Direction Type
Message Type 7.2 BSC -> BTS M
Call Connection Reference 7.10 BSC -> BTS O
Correlation ID 7.3 BSC -> BTSO
a
Cell Identifier List (Forward) 7.13 BSC -> BTS Ob
Cell Identifier List (Reverse) 7.13 BSC -> BTS Ob
Forward Burst Radio Info 7.25 BSC -> BTS Oc
Reverse Burst Radio Info 7.26 BSC -> BTS Od
IS-2000 Forward Power Control Mode 7.27 BSC -> BTS Oe
IS-2000 FPC Gain Ratio Info 7.28 BSC -> BTS Of
Abis To ID 7.22 BSC -> BTSO
g
a. Optionally included by the source BS. If included, the value shall be8saved and used by the target BS on Abis signaling messages.9
b. The length field of this element shall be set to ‘0’ if no resources are to10be allocated in the indicated direction.11
c. This element is only included when forward link radio resources are to12be allocated to the burst.13
d. This element is only included when reverse link radio resources are to14be allocated to the burst.15
f. This element shall be included when supporting a secondary power16 control subchannel. It provides information used for forward gain17equalization for the SCH.18
e. Thi s element shall be included when supporting a secondary power19control subchannel for the SCH. The FPC_MODE value shall go into20
effect at the earlier of the burst start times indicated in the Forward1Burst Radio Info and/or Reverse Burst Radio Info element.2
g. This element is required if an Abis From ID value was included in an3Abis BTS Setup Ack message previously received from the BS for this4call association.5
The following table contains lists of all elements that make up the messages defined in4Chapter 7.The table includes the Information Element Identifier (IEI) coding which5distinguished one element from another.6
7
Table7-1 Abis Information Element Identifiers Sorted by Identifier value8
Element Name Identifier Interface(s) Reference
(unused value – available) 01H
(unused value – available) 02H
Service Option 03H Abis,A1 6.2.2.96
Cause 04H Abis,A1 6.2.2.125
(unused value – available) 05H
(unused value – available) 06H
Frame Selector Info FFS Abis,A7 6.2.2.14
Quality of Service Parameters FFS Abis,A1 6.2.2.54
This element contains an ident ifier chosen by the BSC for its own use in quickly process ing7Abis signaling messages received from the BTS. For example, it may be used to identify8
the resources supporting the cal l association that are internal to the BSC. If an Abis From9ID is supplied by this BSC, then the BTS includes this in the Abis To ID element in10subsequent Abis messages to this BSC.11
127 6 5 4 3 2 1 0 Octet
Abis Element Identifier 1
Length 2
(MSB) Abis From ID 3
(LSB) • • •
Length: This field indicates the number of octets in this element13following the Length field. The maximum value in this14version of this specification is 2 octets.15
Abis From ID: This field has variable length. The actual length is16indicated in the Length field and is dependent upon the17particular implementation. In this version of this18standard, this value shall be no more than 2 octets long.19
7.22 Abis To ID20
This element conta ins an identifier chosen by the BSC for its own use in quickly process ing21Abis signaling messages.22
If an Abis From ID was supplied by the BSC, then the BTS includes this value in the Abis23To ID element in subsequent Abis messages to the BSC.24
Length: This field indicates the number of octets in this element1following the Length field. The maximum value in this2version of this specification is 2 octets.3
Abis To ID: This field has variable length. The actual length is4indicated in the Length field and is dependent upon the5particular implementation. In this version of this6standard, this value shall be no more than 2 octets long.7