1、m 3404583 00807b3 430 W , Released: 1 July 1993 GSM 08.52 Version: 4.0.1 Date: 1 July, 1993 Work Item No: Key words: European digital cellular telecommunication system (phase 2); Base Station Controller (BSC) to Base Transceiver Station (BTS) Interface Principles ETSI European Telecommunications Sta
2、ndards Institute ETSI Secretariat: Route des Lucioles, F-O692 1 Sophia Antipolis Cedex . France TP. + 33 92 94 42 O0 TF. + 33 93 65 47 16 Tx. 47 O0 40 F This is an unpublished work the copyright in which vests in the European Telecommunications Standards Institute. All rights reserved. The informati
3、on contained herein is the property of ETSI and no part may be reproduced or used except as authorised by contract or other written permission. The copyright and the foregoing restriction on reproduction and use extend to all media in which the information may be embodied. 3404583 O080764 377 D Page
4、 3 GSM 08.52 . version 4.0.1 : July 1993 CONTENTS 1 . 2 . 3 . 4 . 6 . SCOPE 5 DEFINITIONS . 5 2.1 . Base Station System. BSS 5 2.2. Base Station Controller. BSC . 5 2.3. Base Transceiver Station. BTS 5 2.4. Cell . 5 2.5. Transceiver. TRX 5 2.6. Base Control Function. BCF 5 GENERAL 6 FUNCTIONAL DIVIS
5、ION BETWEEN BSC AND BTS . 7 4.1. General 7 4.2. Terrestrial Channel Management . 7 4.3. Radio Channel Management 7 4.3.1 . Channel Configuration Management . 7 4.3.2. SDCCH (stand alone DCCH) and TCH Management 7 4.3.2.1 . Frequency hopping management 7 4.3.2.2. Channel selection. link supervision a
6、nd channel release . 7 4.3.2.3. Power Control . 8 4.3.2.4. Idle channel observation . 8 4.3.3. BCCHKCCH Management 8 4.3.4. Random Access 8 4.3.5. Channel Coding/Decoding . 8 4.3.6. Transcoding/Rate Adaption . 8 4.3.7. Timing advance . 9 4.3.8. Radio Resource Indication . 9 4.3.9. Measurements 9 4.3
7、.1 O . LAPDm functions (Layer 2) 9 4.3.1 1 . Paging . 9 4.3.12. Handover . 10 4.3.1 3 . Encryption . 10 4.3.14. Mobility Management and Call Control . 10 5.1 . Transcodingrnate Adaption in BTS . 13 5.2. Transcoding/Rate Adaption outside BTS . 13 INTERFACE STRUCTURES . 13 6.1 . Communication Channels
8、 . 13 6.2. Signalling Links . 14 6.3. Signalling Model . 16 Previous page is blank - 3404583 00807b5 203 e Page 5 GSM 08.52 - version 4.0.1 : July 1993 1. SCOPE The use and general aspects of the A-bis interface are given in Technical Specification GSM 08.51. This specification gives the principle b
9、asis for the rest of the specifications specifying the interface between the Base Station Controller, BSC, and the Base Transceiver Station, BTS, with its transceivers, TRX. These components together form the Base Station System, BSS. (The interface between MSC and the BSS is specified in Technical
10、Specifications GSM 08.01 - 08.20.) The intention with this interface is to get a unified way of connecting remotely located BTSsflRXs to a BSC allowing for the interconnection of BSCs and BTSsTTRXs from different manufacturers. In order to keep the BTS as simple as possible, BTS contains only those
11、functions which have to recide close to the radio interface. 2. DEFINITIONS 2.1. Base Station System, BSS See TS GSM 01.04. 2.2. Base Station Controller, BSC See TS GSM 01.04. 2.3. Base Transceiver Station, BTS See TS GSM 01.04. The BTS can consist of one or more TRXs with or without common control
12、equipment. 2.4. Cell See TS GSM 01.04. 2.5. Transceiver, TRX The Transceiver, TRX, in the GSM PLMN is the functional entity which supports the 8 basic radio channels of the same TDMA-frame. 2.6. Base Control Function, BCF A functional entity which handles common control functions within a BTS, e.g.
13、frequency hopping sequencies etc. At a multi BTS site, one of the BCFs can also be choosen to perform functions common to the site (e.g. external alarms, power supply, time base). Previous page is blank 3404583 00807bb L4T A-bis I 1 A-bis I I Page 6 GSM 08.52 - version 4.0.1: July 1993 r TRX BTS1 BC
14、F - TRX TRX BTS2 TRX BCF _-_ _-_ -_ t 3. GENERAL BSC * Technical Specifications GSM 08.01 - 08.20 specify the .mctional split and interface between MSC and the Base Station System, BSS, the A- interface. The BSS can be further subdivided into one BSC controlling one or more BTSs, each consisting of
15、one or more TRXs. The interface treated by this specification is the interface between a ESC and a BTS. It is denoted the A-bis-interface. The A-bis-interface is capable of supporting three different internal BTS configurations: - one single TRX, - - Figure 3.1 shows some possible configurations. a
16、collection of TRXs where all are served by a common physical connection, a collection of TRXs, each served by its own physical connection. BSS I I A-bis I I I I I Lf 1 I il MSC I I BTS3 Figure 3.1108.52. BSS Subdivision and Interfaces. . W 3404583 O080767 O86 Page 7 GSM 08.52 - version 4.0.1 : July
17、1993 This specification is based on the use of digital transmission system interfaces, either at 2048 kbit/s or at 64 kbit/s. furthermore, the use of a subrate of 16 kbit/s is supported for coded speech or rate adapted data. This interface will support the transcoder positioned either inside or outs
18、ide BTS. In the latter case, remote control (synchronisation) of the transcoder is used. 4. FUNCTIONAL DIVISION BETWEEN BSC AND BTS 4.1. General In Technical Specification GSM 08.02 the functional division between MSC and BSS is described. This section describes the further subdivision of functions
19、between BSC and BTSiTRX required for the A-bis interface. A summary can be found in Table 4.1. Some general requirements on the functionality of the A-bis interface are also specified. 4.2. Terrestrial Channel Management There is a unique mapping from traffic channels on the radio path to the terres
20、trial traffic channels. BSC makes the choice of radio channel and thereby also of the terrestrial channel for a call, 4.3. Radio Channel Management 4.3.1. Channel Configuration Management The channel configuration is controlled between the BSC and OMC. Current configuration is downloaded from OMC to
21、 BSC which then controls the use of the radio channels (TDMA time slots for BCCHCCCH, TCHs, SDCCHs etcl. 4.3.2. SDCCH (stand alone DCCH) and TCH Management 4.3.2.1. Frequency hopping management The hopping sequences for each BTS (cell) is downloaded from OMC to BSC. It is then the responsibility of
22、BSC to download this information to each BTS and also to send the COireSpOndinQ BCCH information to be transmitted in the BCCH time slots. 4.3.2.2. Channel selection, link supervision and channel release These functions are controlled by BSC. For channel selection BSC has to have information on bloc
23、ked radio channels and also on interference level on idle channels. In the assignment messages to MS (Immediate Assign, Assign Command and Handover Command), a Starting Time parameter is included. This starting time is based on the frame number on the (new) BTS. Before sending the assign message to
24、MS, BSC has to be informed on the current frame number in BTS. When assigning a channel, BSC shall inform BTS on relevant parameters, e.g. channel type, channel coding, rate adaption, starting time. 3404583 O080768 Tb2 W Page 8 GSM 08.52 - version 4.0.1 : July 1993 9 4.3.2.3. Power Control The order
25、ed MS power level is sent in the 16 bit L1 -header of SACCH- blocks on the downlink and the actual power level used by MS is reported in the corresponding L1-header on the uplink. This header is inserted (downlink) and extracted (uplink by BTSTTRX. The determination of required power level in MS is
26、based on uplink radio measurements made by BTSTTRX and reported to BSC. The basic control of this power is performed by BSC and the dynamic regulation is performed by BSC or optionally by BTS. If BTS supports dynamic MS power regulation, BSC can indicate whether BTS is to regulate the MS power and i
27、f so, also the parameters required by BTS. The required TRX transmission power level on a channel is based on reported measurements performed by MS. The dynamic control of this power is optional. If supported, the basic control is performed by BSC and the dynamic regulation is performed by BSC or op
28、tionally by BTS. If BTS supports dynamic TRX transmission power regulation, BSC can indicate whether BTS is to regulate the transmission power and if so, also the parameters required by BTS. 4.3.2.4. Idle channel observation Idle channels are monitored by BTS. 4.3.3. BCCH/CCCH Management TRX knows t
29、he timing of BCCHICCCH slots (not known by BSC. The actual timing of BCCHKCCH blocks therefore has to be made by BTSnRX, including the scheduling of Paging Request messages on paging sub- channels. BCCH information is downloaded to BTS. 4.3.4. Random Access Detection of a random access attempt has t
30、o be made by TRX which then sends a message to BSC containing the required timing advance, the frame number of the access attempt and the 8 bit Channel Request message sent by MS in the access burst. This information is then included by BSC in the following Immediate Assign message sent to MS. 4.3.5
31、. Channel CodmglDecoding The error protection coding and decoding is made by BTSTTRX. Different coding and interleaving schemes are used for speech and data calls. This information has to be signalled from BSC to BTS on a per call basis. 4.3.6. Transcoding/Rate Adaption The A-bis interface has to al
32、low for the transcoderhate adaptor being positioned either inside or outside BTS. = 3404583 0080767 959 Page 9 GSM 08.52 - version 4.0.1 : July 1993 4.3.7. Timing advance Timing advance has to be determined by TRX. When MS is on a dedicated channel (SDCCH, TCH), the required timing advance (TA) is s
33、ent to MS and the actual timing advance is reported by MS in the 16 bit L1 -header of the SACCH blocks. At handover access, TA is determined by TRX and reported to MS in the PHYsical INFOrmation message sent by BTSKRX. At random access, TA is determined by TRX but in those cases, TA has to be report
34、ed to BSC for inclusion in the IMMediate ASSIGN message sent to MS by BSC. 4.3.8. Radio Resource Indication BTS reports on status (interference level, blocking etc.) of idle channels to BSC on a regular basis. 4.3.9. Messurementa MS measures the downlink received level and quality from the serving c
35、ell and the received level from surrounding cells. The results from these measurements are reported by MS in Measurement Report messages on SACCH. Uplink received level and quality are measured by BTS/TRX. The parameters for the uplink measurements are equivalent to the parameters used by MS for the
36、 corresponding downlink measurements (averaging period and dynamic range). The support of forwarding this basic raw measurement data over the A-bis interface is mandatory. Additionally, BTS and BSC may optionally support some pre-processing in BTS of this data. 4.3.10. LAPDm functions (Layer 2) Laye
37、r 2 on the radio interface (LAPDm) is terminated at BTS/TRX. Between BTS and BSC, LAPD is used. 4.3.1 1. Paging Paging is initiated by MSC via BSC. BSC determines the paging group to be used based on IMSI of the MS to be paged. The paging group value is sent to BTS together with the TMSI or IMSI. Ba
38、sed on the paging group information, BTS/TRX will build the relevant PAGING REQUEST message and execute the transmission of the message in the correct paging sub-channel. Page 10 GSM 08.52 - version 4.0.1: July 1993 4.3.12. Handover No handover recognition or decision is made by BTS. However, BTSfRX
39、 has to detect the handover access made by a handed over MS. BTSTTRX also checks the Handover Reference value sent by MS in the handover access burst against the Handover Reference value received from BSC in the channel activation command. In case of an asynchronous handover, BTS/TRX then builds the
40、 PHYsical INFOrmation message (including the Timing Advance value) and sends it to MS. The handover access is also reported to BSC. 4.3.13. Encryption Encryption and decryption is made of the complete outgoing bit stream (except for preambles/synch words). This therefore has to be made by TRX. The e
41、ncryption key has to be downloaded to BTSTTRX before encryption starts. Special control messages are therefore required between BSC and BTSTTRX. 4.3.14. Mobility Management and Call Control All mobility management and call control functions recide in MSC. M 3404583 0080773 507 I Page 11 GSM 08.52 -
42、version 4.0.1 : July 1993 FUNCTION LOCATION TERRESTRIAL CHANNEL MANAGEMENT BTS BSC/MSC MSC-BSC channels Channel allocation .X Blocking indication X BSC-BTS channels Channel allocation X Blocking indication X RADIO CHANNEL MANAGEMENT Channel configuration management .X Frequency Hopping Management .X
43、 Execution X TCH management Channel allocation (choice) X Link supervision .X Channel release X Idle channel observation . X Power control determination X.X SDCCH allocation .X Link supervision .X Channel release X Power control determination XX SDCCH management (Stand alone DCCH) BCCH/CCCH manageme
44、nt Scheduling of messages Management. X Execution X Random access Access detection. X Immediate assign (access grant) X Channel coding/decoding X Transcoding/rate adaption X Measurements Uplink measuring . X Processing of reports from MS/TRX X.X Traffic measurements . X Note 3 Note 3 Note 1 Note 2 N
45、ote 4 TABLE 4.1. Summary of functional division between BTS and BSC/MSC Page 12 GSM 08.52 - version 4.0.1 : July 1993 BTS BSC/MSC Timing advance Calculation X Signalling to MS at random accescX Signalling to MS at handover.X Signalling to MS during call.X Radio resource indication Report status of i
46、dle channels.X LAPDm functions (Layer 2) X Encryption Management . X Execution X (Key from BSC) Paging Initiation. X DRX paging Management . X Execution. . X Handover BSC internal, one cell . X BSC internal, between cells. . X BSC external recognition, radio reasonX recognition, traffic reason,X dec
47、ision . X execution X Handover access detection X MOBILITY MANAGEMENT Authentication . X Location updating X CALL CONTROL. X TABLE 4.1 . (Continued) Summary of functional division between BTS and BSC/MSC Note 1: Although the transcoder is always controlled by the BTS, it can optionally be located ou
48、tside the BTS (e.g. at the BSC or at the MSC site). In that case, remote control is performed by BTS using inchannel signalling. Note 2: Including averaging comparable to what is done in the MS. Note 3: The support of power level determination in BTS is optional. Note 4: The support of forwarding al
49、l raw measurement data from MSTTRX over the A-bis interface and the processing of it in BSC is mandatory. The BTS/BSC may additionally support also some pre- processing in BTS of this raw data. - W 3404583 0080773 38T Page 13 GSM 08.52 - version 4.0.1 : July 1993 5. TRANSCODINGIRATE ADAPTION AND MULTIPLEXING The interface supports two options: transcodinghate adaption performed in BTS or outside BTS. 5.1. Transcoding/Rate Adaption in BTS The transcoding of speech to normal 64 kbit/s A-law is performed within BTS. Data may be rate adapted or submultiplexed to 64 kbit/s circuits.
