CELLULAR SYSTEMS BSS R&D A ctivity ctivity Release 4 REFERENCE
DC
AUTHOR
DATE
3BK 11202 0051 DSZZA
MCD
O. BESSET
12/09/97
TITLE : PAGING AND ACCESS GRANT CONTROL
TYPE SPE VERSION
ACTIVITY
PAGES
4.4.0.0
SYS-TLA
30
CS DOC CENTRE VISA
ABSTRACT (Purpose of the document, highlights, ,...) :
This document describes the Paging and Access Grant Control within the BSS.
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IIV IIV IIV
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BSC
PAGING AND ACCESS GRANT CONTROL
APPROVAL
Version 4.4 4.4.0.0 NAME FUNCTION SIGNATURE
Ed 03 3BK 11202 0051 DSZZA
D. Berthoumieux AM
V. Steegmans BSC SSAM
L. Szabo BTS SSAM
2
DOCUMENT HISTORY Release 1 : TLA/145 Version
Date
Author
Reason for update
1.1.0.0
14.01.91
B.Maier
TLA approved version.
Author
Reason for update
Release 2 : S/P2/3.4.1.1.1 Version
Date
The next three references are not version of this document but specification notes written for the release 2. 2.1.0.0 2.1.0.0 2.2.0.0
31.01.92 04.03.92 24.04.92
M.Montagna L.Poisson M.Roberts
TLA/SN/12 - Paging over A - Interface. TLA/SN/13 - RR Paging Channel Management. TLA/SN/11 - CCCH Management.
2.0.0.0 2.0.0.1 2.0.0.2 2.0.1.0
26.10.92 15.01.93 19.02.93 22.04.93
K.Hofbauer K.Hofbauer K.Hofbauer K.Hofbauer
2.1.0.0
08.06.93
K.Hofbauer
First draft - TLA - document. Second draft - TLA - document. Third draft - TLA - document. TLA approved, according meeting minutes RSG/160. RSG approved, according meeting minutes TLA/153.
Release 3 : 3BK 11202 0000 DSZZA Version
Date
Author
3.0.0.0 3.0.0.1
27.12.93 18.02.94
P.Vincent P.Vincent
3.0.1.0
06.04.94
P.Vincent
3.1.0.0
27.05.94
P.Vincent
Reason for update First draft for release 3.0. It includes CRQ/317. This second draft takes into account the written comments from AJ.Caldwell, M. Roberts, C. Dem Demar arez ez and and M.Do M.Dobr bros osie iels lski ki.. Reviewed after TLA meeting (minutes in SYS/022) Approved version taking into account editorial comments (see minutes in SYS/051).
Release 4 : 3BK 11202 0051 DSZZA Version
Date
Author
4.0.0.0 4.0.1.0
10.11.94 09.12.94
P. Vincent P. Vincent
4.1.0.0 4.2.0.0 included. 4.3.0.0 4.4.0.0
30.12.94 14.10.96
P. Vincent F. d'Argence
First draft for release 4. It includes CRQ/750. Level 1 approval after TLAr4#4 meeting (see SYS/111). Level 2 approved version after mail approval. CRQ/2086 + editorial remarks from IIV
21.05.97 12.09.97
F. d’Argence O. Besset
Inclusion of CR 015147. Inclusion of CRQ/2863.
Ed 03 3BK 11202 0051 DSZZA
Reason for update
3
TABLE OF CONTENTS
1. INTRODUCTION .....................................................................................................................5 1.1 SCOPE ................................................................................................................................... 5 1.2 REFERENCES .......................................................................................................................5 1.2.1 GSM References..................................................................................................................5 1.2.2 Doctree References .............................................................................................................5 1.3 GLOSSARY............................................................................................................................ 6 2. FUNCTIONAL DESCRIPTION ...............................................................................................7 2.1 GENERAL DESCRIPTION......................................................................................................7 2.2 THE CCCH ORGANISATION .................................................................................................8 2.2.1 TDMA frame organisation.....................................................................................................8 2.2.2 Sharing the CCCH................................................................................................................8 2.2.3 The CCCH Group.................................................................................................................9 2.2.4 The Paging Group................................................................................................................10 2.2.5 Example............................................................................................................................... 10 2.2.6 Dimensioning .......................................................................................................................11 3. DYNAMIC BEHAVIOUR .........................................................................................................13 3.1 MESSAGE EXCHANGE .........................................................................................................13 3.1.1 Paging scenario....................................................................................................................13 3.1.2 Immediate assignment scenario ...........................................................................................14 3.2 DETAILED BEHAVIOUR WITHIN THE BSC...........................................................................15 3.2.1 Paging Procedure.................................................................................................................15 3.2.2 Access Grant Procedure ......................................................................................................16 3.3 DETAILED BEHAVIOUR WITHIN THE BTS ...........................................................................17 3.3.1 Paging Procedure.................................................................................................................17 3.3.2 Paging queues .....................................................................................................................19 3.3.3 Access Grant Procedure ......................................................................................................20 3.4 TELECOM AND O&M INTERWORKING WITHIN THE BSS...................................................22 3.4.1 Configuration Management...................................................................................................22 3.4.2 Performance Management ...................................................................................................23 3.4.3 Error Reporting.....................................................................................................................23 4. INTERFACE DESCRIPTION ..................................................................................................24 4.1 GSM INTERFACES/PHYSICAL INTERFACES.......................................................................24 4.1.1 A Interface ........................................................................................................................... 24 4.1.2 Abis Interface....................................................................................................................... 25 4.1.3 Air Interface.......................................................................................................................... 26 4.2 INTERNAL INTERFACES.......................................................................................................27 4.3 EXTERNAL INTERFACES......................................................................................................27 4.4 TIMERS LIST.......................................................................................................................... 27 4.5 PARAMETERS LIST...............................................................................................................28 5. OPEN POINTS ........................................................................................................................30 6. FUTURE IMPROVEMENTS....................................................................................................30 7. RELEA SES CHANGES ..........................................................................................................30 8. FEATURES .............................................................................................................................30
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1. INTRODUCTION 1.1 SCOPE This document describes the Paging and Immediate Assignment procedures for release 4 in regard to the BSS. This document has to be read with the relevant GSM Technical Specifications. The management of multiple CCCH slots (CCCH_CONF > 1) is not part of this release. All the references to this feature are only informative.
1.2 REFERENCES 1.2.1 GSM References [1] GSM 04.06 - MS-BSS interface data link layer specification. [2] GSM 04.08 - Mobile Radio Interface Layer 3 Specification. [3] GSM 05.02 - Multiplexing and Multiple Access on the radio path. [4] GSM 08.58 - Base Station Controller (BSC) to Base Transceiver Station (BTS) interface : Layer 3 specification. [5] GSM 08.08 - Mobile Switching Centre (MSC) to Base Station System (BSS) interface : Layer 3 specification. The version numbers of the GSM Technical Specifications used in this release are given in [12].
1.2.2 Doctree References [6] Radio and link establishment [7] Application document 08.58 [8] Application document 08.08 [9] Application document 04.08 (RR) [10] Protocol error handling [11] BSS configuration management [12] Alcatel BSS application document to GSM - General overview [13] SMS Cell Broadcast [14] R4-x Telecom Specification Header Document
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1.3 GLOSSARY AGCH BSC BSS BTS CBCH CCCH CGI CI CR FN FUCO IE IMSI LAC LAI MCC MNC MS MSC OMU OMC-R PCH RACH SBL SCCP SDCCH TMSI
Access Grant CHannel Base Station Controller Base Station System Base Transceiver Station Cell Broadcast CHannel Common Control CHannel Cell Global Identifier Cell Identifier Connection Request Frame Number Frame Unit COntroller Information Element International Mobile Subscriber Identity Location Area Code Location Area Identifier Mobile Country Code Mobile Network Code Mobile Station Mobile Switching Centre Operation and Maintenance Unit Operation and Maintenance Centre Radio Paging CHannel Random Access CHannel Security BLock Signalling Connection Control Part Stand alone Dedicated Control CHannel Temporary Mobile Subscriber Identity
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2. FUNCTIONAL DESCRIPTION 2.1 GENERAL DESCRIPTION The paging function allows the PLMN-network to find a mobile subscriber, who is roaming in it. The location area, the MS is just roaming was sent to the MSC in the last location update procedure. Such a location area can consist of one or more cells, maybe controlled by different BSCs. As paging messages can be sent via different cells on the radio interface, only the MSC can recognize, if a paging answer from the MS corresponds to a former paging message. For the Alcatel BSS, the paging and the answer to the paging are completely independent procedures. The paging response is one reason, that a mobile will try to establish a signalling connection to the network. Other reasons could be an emergency call, originating call, etc.. This signalling link establishment procedure is described in the section describing the Access Grant control and in ref[11]. In order to pass information to or from the MS, if there exists no dedicated signalling connection between MS and network, GSM defines the channel type - CCCH. Depending on the expected traffic, different channel combinations are possible. They are set within the configuration data generated by the O&M - function. Up to 4 timeslots can carry CCCH information (this option is not supported by this release). In the downlink CCCH, there exists a fixed relationship of PCH and AGCH (defined by the system parameter BS_AG_BLKS_RES). In the Alcatel BSS implementation, it is not foreseen to pass AGCH - messages also on PCHs if some blocks are reserved for AGCH. In the case that no block is reserved for AGCH (BS_AG_BLKS_RES=0), the AGCH message is sent on PCH. The PCH is subdivided in PCH - Subchannels. Each subchannel corresponds to a specific paging group and can contain one L3 - paging message (maximum of 8 PCH-subchannels per multiframe). The paging group and the CCCH - group(TS0,TS2,TS4,TS6) is derived from the IMSI of the MS. The MS also has to analyse the Control channel description IE within the SYSTEM INFORMATION TYPE 3 - message in order to get the knowledge about the CCCH - organisation. Thus the MS needs not to listen to all PCH - Subchannels in the CCCH, but only to that one of its own paging group. This is called discontinuous reception (paging DRX) and enables the MS to power itself down, if no paging message is expected. The occurence of a specific paging group can vary from 2 * duration of a CCCH-multiframe (470.76ms) to 9 * duration of a CCCH-multiframe (2118.42 ms). The following paging features are not supported by this release of the Alcatel BSS : - support of mulitple CCCH slots, - paging reorganisation mode, - paging repetition performed by the BSS, - extended paging mode, - use of Immediate Assignment Extended message, - use of Immediate Assignment Reject message, - use of the channel needed information in the paging message.
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2.2 THE CCCH ORGANISATION 2.2.1 TDMA frame organisation The PCH is carried on the CCCH downlink. Two possible organisations for the logical channels are foreseen by GSM (refer to GSM 05.01) : BCCH and CCCH BCCH, CCCH and SDCCH/C4 This distinction is given either by the parameter CCCH_CONF or by the parameters BS_CC_CHANS and BS_CCCH_DCCH_COMB. TS GSM 04.08 [2] uses only CCCH_CONF and GSM 05 series namely TS GSM 05.02 [3] uses BS_CC_CHANS and BS_CCCH_DCCH_COMB. Table 1 gives the correspondence between the two possibilities.
CCCH_CONF
BS_CC_CHANS
BS_CCCH_DCCH_COMB
0
1
no
1
1
yes
2
2
no
4
3
no
6
4
no
Table 1 : Correspondence between Paging parameters
As given in TS GSM 05.02 [3], the list of permitted BCCH/CCCH channel combinations is : (iv) FCCH + SCH + BCCH + CCCH (v) FCCH + SCH + BCCH + CCCH + SDCCH/4(0..3) + SACCH/C4(0..3) (vi) BCCH + CCCH where CCCH = PCH + RACH + AGCH Note : the channel combination (v) is allowed if there is only one CCCH slot.
2.2.2 Sharing the CCCH The CCCH downlink is shared by two types of channel : the AGCH, the PCH. Note : The AGCH is used to send to Mobile Stations, the "IMMEDIATE
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ASSIGNMENT" (or IMMEDIATE ASSIGNMENT EXTENDED or REJECT, not used in this release) message in order to give them a dedicated channel. The Immediate Assignment procedure takes place at the beginning of the transaction, after the Mobile Station has accessed the network by a Random Access burst. A parameter, BS_AG_BLKS_RES, gives the number of CCCH blocks allocated to the AGCH. The value of this parameter is in the interval 0 to 7 or 0 to 2 if the value of CCCH_CONF is equal to 1 (or if BS_CCCH_DCCH_COMB is true). But there is always, at least, one block reserved for one PCH .
When the AGCH is present, it occupies the BS_AG_BLKS_RES first CCCH blocks. Figure 1 gives a 51 TDMA frame with 9 CCCHs out from which 3 blocks are reserved for the AGCH. Figure1 : Example of AGCH and PCH CCCH 0
CCCH 1
CCCH 2
CCCH 3
CCCH 4
Reserved for AGCH
CCCH 5
CCCH 6
CCCH 7
CCCH 8
6 CCCH blocks are available for the PCH
2.2.3 The CCCH Group The CCCH Group informs the MS on which CCCH slot (of those which are available), it should listen to. So it is also used in the Immediate Assignment procedure. It is computed as described hereafter : CCCH_GROUP = ((IMSI mod 1000) mod (BS_CC_CHANS * N)) div N
with BS_CC_CHANS = number of basic physical channels supporting CCCH (range 1..4) BS_CC_CHANS is derived from CCCH_CONF (see table 1). The combination of BS_AG_BLK_RES and BS_PA_MFRMS gives the number of paging groups. This number is called N. It is obtained when multiplying the number of paging blocks "available" on one CCCH slot by BS_PA_MFRMS (see paragraph related to dimensioning for the range of each parameter). BS_PA_MFRMS gives the number of 51-TDMA frames reserved for the transmission of CCCH blocks over at least 2 TDMA frames (with a maximum of 9). The following table gives the relationship between the CCCH_GROUP number and the CCCH slot used. CCCH_GROUP
TS
0
0
1
2
2
4
3
6
Table 2 : correspondence between CCCH_GROUP and TS concerned
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2.2.4 The Paging Group The Paging Group is a number allocated to a Mobile Station which allows it to listen to a specific CCCH block over all the TDMA frames reserved for the Paging Channel. With this number, the formula of which is given below, the Mobile Station is not obliged to listen to all the CCCH blocks. It can wake up at the relevant time only. This is the DRX Paging. PAGING_GROUP = (( IMSI mod 1000 ) mod ( BS_CC _CHANS * N )) mod N
The formula giving the Paging Group can be simplified to become : PAGING_GROUP = ( IMSI mod 1000 ) mod N
The paging parameters are broadcast on the BCCH within the "SYSTEM INFORMATION" messages into the "Control Channel Description" parameter of "SYSTEM INFORMATION TYPE 3" message. Each MS knowing the CCCH organisation, has access to all the parameters previously defined. The Mobile Station is able to calculate its Paging Group and its CCCH Group (the same calculation is also performed by the BSC).
2.2.5 Example Figure 1 gives an example of the 51 TDMA frames and Paging Group with the following set of parameters : CCCH_CONF = 0 ==> the CCCH_GROUP has only the zero value (CCCH on TS 0) ==> The number of CCCH blocks per frame is equal to 9 (no SDCCH). BS_AG_BLKS_RES = 3 ==> There are 6 (9-3) CCCH blocks reserved for paging. BS_PA_MFRMS = 4 ==> 4 consecutive 51 TDMA Frames are used for one cycle on all the available paging groups. All these values imply that the parameter N takes the value 24. There are 24 Paging Groups (24 = 6 * 4).
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Figure 2 : Example of CCCH organisation First 51-TDMA frame AGCH
AGCH
AGCH
PGR 0
PGR 1
PGR 2
PGR 3
PGR 4
PGR 5
PGR 9
PGR 10
PGR 11
PGR 15
PGR 16
PGR 17
PGR 21
PGR 22
PGR 23
Second 51-TDMA frame AGCH
AGCH
AGCH
PGR 6
PGR 7
PGR 8
Third 51-TDMA frame AGCH
AGCH
AGCH
PGR 12
PGR 13
PGR 14
Fourth 51-TDMA frame AGCH
AGCH
AGCH
PGR 18
PGR 19
Reserved for the AGCH
PGR 20
PGR : Paging Group (from 0 to 23)
2.2.6 Dimensioning The values given hereafter are relative to one CCCH slot. In case of several channels, the global dimension for the whole BTS is obtained by multiplying these values by the number of common channels. - BS-AG-BLKS-RES 0 - 2 if CCCH_CONF = 1 0 - 7 if CCCH_CONF
1
- BS_PA_MFRMS : min value 2 max value 9 - Number of PCH blocks available per 51 TDMA frames min value 1 or 2 according to CCCH_CONF max value 3 or 9 according to CCCH_CONF The minimum value is determined according to the following conditions : CCCH_CONF = 1 => 3 CCCH Blocks are available for AGCH and PCH. On these 3 CCCH blocks, up to 2 (Max value of BS_AG_BLKS_RES) are reserved for AGCH. So it remains 1 CCCH block for PCH information.
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CCCH_CONF
1 => 9 CCCH Blocks are available for AGCH and PCH.
On these 9 CCCH blocks, up to 7 (Max value of BS_AG_BLKS_RES) are reserved for AGCH. So it remains 2 CCCH block for PCH information. The maximum value (3 or 9) is determined according to the following conditions : CCCH_CONF = 1 => 3 CCCH Blocks are available for AGCH and PCH. On these 3 CCCH blocks, 0 block is reserved for AGCH. So it remains 3 CCCH blocks for PCH information. CCCH_CONF
1 => 9 CCCH Blocks are available for AGCH and PCH.
On these 9 CCCH blocks, 0 block is reserved for AGCH. So it remains 9 CCCH blocks for PCH information. - BS_CC_CHANS = 1…4 depending on the value of CCCH_CONF (see table 1) - N ( Number of Paging Groups) min value 2 max value 81 N is obtained when multiplying BS_PA_MFRMS by the number of paging blocks available per 51 TDMA frame. The min value is determined with BS_PA_MFRMS equal to 2 and Number of PCH equal to 1. The max value is determined with BS_PA_MFRMS equal to 9 and Number of PCH equal to 9.
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3. DYNAMIC BEHAVIOUR 3.1 MESSAGE EXCHANGE 3.1.1 Paging scenario
MSs Radio Channel
1 2 1a 2a 3a
3b
BTS
BSC
MSC
PAGING (MS1) <----------------------------------------Start T3113 PAGING COMMAND (MS1,pgr1) for MS1 <-----------------------------------------PAGING (MS2) <----------------------------------------PAGING COMMAND (MS2,pgr1) Start T3113 <-----------------------------------------for MS2 PAGING REQUEST TYPE 1 <-------------PCH,pgr1-------------(Repeated for MS3 - MS9) (MS1,MS2) ( Repeated for MS3-MS5 of PAGING REQUEST TYPE 2 pgr2, for MS6-MS9 of pgr4) <-------------PCH,pgr2-------------(MS3,MS4,MS5)
3c
PAGING REQUEST TYPE 1 <-------------PCH,pgr3-------------(No Identity)
3d
PAGING REQUEST TYPE 3 <-------------PCH,pgr4-------------(MS6,MS7,MS8,MS9)
4 Access Grant scenario for all MSs which answer to a Paging Request
PAGING RESPONSE (MSn) ----------SDCCH-------------------->------------------------------------------>--------------------------------------> Stop T3113 for MSn Note : This scenario is for one CCCH-group only. The numbers on the left side refer to the function description in sections 3.2.1 and 3.3.3. 5
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3.1.2 Immediate assignment scenario
MSs
1 2 3 4 5 6
Note :
Radio Channel
BTS
BSC
CHANNEL REQUEST ------------------------RACH---------------------------> Start T3120 CHANNEL REQUIRED ------------------------------------------------------------> CHANNEL ACTIVATION <-----------------------------------------------------------CHANNEL ACTIVATION ACK ------------------------------------------------------------> IMMEDIATE ASSIGN COMMAND <-----------------------------------------------------------IMMEDIATE ASSIGNMENT <-----------------------AGCH---------------------------Stop T3120
This scenario is for one CCCH-group only. The numbers on the left side refer to the function description in sections 3.2.2 and 3.3.2
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3.2 DETAILED BEHAVIOUR WITHIN THE BSC 3.2.1 Paging Procedure The following, describes the detailed behaviour within the BSC. The given number refers to the steps as indicated on the left side of the scenario in section 3.1.1 .
1: MSC has sent a PAGING message in connectionless mode and has started the timer T3113 to 1a: supervise the PAGING RESPONSE message from the MS. The MSC may repeat the paging if no answer arrives in time. The following tasks have to be done by the BSC: A. BSC performs message input check For the message format checking, refer to [10]. Cell Identifier list no IE present or incorrect discr. = C.G.I(MCC+MNC+LAC+CI)
discr. = LAC + CI discr. = LAI(MCC+MNC+LAC)
discr. = LAC discr. = all discr = CI discr. = no cell
performed task paging is performed on all cells, controlled by the BSC for each C.G.I, which points to one specific cell, a paging task is performed. If not all the C.G.I's are known in the BSC, the paging is performed on all cells . same task as for C.G.I, except that only LAC + CI is checked. on each cell of the defined LAIs, paging task is performed If not all the LAIs are known, paging is performed on all cells controlled by the BSC. same task as for LAI, except that only LAC is checked. paging is performed on all cells, controlled by the BSC paging is performed on all cells, controlled by the BSC. paging is performed on all cells, controlled by the BSC.
B.BSC calculates the paging group The paging group which is contents of the PAGING COMMAND message is calculated with the following equation: PAGING_GROUP(0 ... N-1) = ((IMSI mod 1000) mod (BS_CC_CHANS*N)) mod N N = NUM_PB_PER_51_MFRMS * BS_PA_MFRMS BS_CC_CHANS : number of CCCH- timeslots (1-4) NUM_PB_PER_51_MFRMS : number of PCH - Subchannels per CCCH - multiframe BS_PA_MFRMS : number of CCCH- multiframes between transmission of the same paging group
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C.BSC calculates the CCCH - timeslot In the first step the CCCH_GROUP is calculated: CCCH_GROUP(0, ... , BS_CC_CHANS -1) = ((IMSI mod 1000)mod (BS_CC_CHANS*N)) div N In the second step, the CCCH - timeslot is calculated according following table.
CCCH_GROUP 0 1 2 3
CCCH-timeslot 0 2 4 6
D.BSC generates the Abis - PAGING COMMAND - message and sends it to the BTS
2: BSC sends to each BTS(depending on its SBL BTS_TEL, paging is not performed for disabled 2a: cells), which controls one of the indicated cells of the Cell Identifier List, a PAGING COMMAND message. The Channel Number - IE within the Message header is set to the calculated 'CCCH - timeslot' (step C). The Paging Group - IE is set according the equation in step B. The MS Identity is set to the TMSI, if TMSI was sent in the PAGING - message via the A-Interface, if not, to the IMSI. 4: Access Grant procedure is performed as described in section 3.2.2. 5: After the successful allocation of the SDCCH see ref [11].
3.2.2 Access Grant Procedure The Access Grant Procedure is described here mainly in relation to the RACH and AGCH and only the successful allocation of a SDCCH is shown. For the detailed protocol behaviour, refer to [11]. 2: CHANNEL REQUIRED message is received from the BTS, as the reaction, that the BTS has successfully recognized a CHANNEL REQUEST message on the RACH. 3: BSC sends the CHANNEL ACTIVATION message to the BTS, in order to allocate a dedicated signalling connection(SDCCH) to the MS. 4: After the successful SDCCH allocation the CHANNEL ACTIVATION ACK is received from the BTS. 5: After this successful SDCCH allocation, the IMMEDIATE ASSIGN COMMAND is sent to the BTS. The Request reference IE within the Immediate Assign Info IE is set to the value received in the CHANNEL REQUIRED message before. The MS will compare this Request reference value with its own one in order to see if it corresponds to one of its 3 former Channel requests.
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The IMMEDIATE ASSIGNMENT has to be sent on the same CCCH -timeslot as the received CHANNEL REQUEST message. That means, that the timeslot in the Channel Number IE of the CHANNEL REQUIRED message must be the same than in the IMMEDIATE ASSIGN COMMAND.
3.3 DETAILED BEHAVIOUR WITHIN THE BTS 3.3.1 Paging Procedure The following, describes the detailed behaviour within the BTS. The given number refers to the steps as indicated on the left side of the scenario in section 3.1.1 . 3 BTS receives the PAGING COMMAND message from the BSC. As the receiving of this message is not time synchronous with the transmission of the PAGING REQUEST - message on the AIR - Interface, there is the need to store the PAGING REQUEST -messages. in a transmission buffer, until a request to send (RTS) from the layer 1 function happens. Following paragraph is applicable only to Release 4 sub-releases NOT including CR 015147 (see ref [14] for details) { There is one buffer defined for each paging group and per each defined CCCH group. The buffer is organized according the FIFO principle.(see next section)
} Following paragraph is applicable only to Release 4 sub-releases including CR 015147 (see ref [14] for details) { There is one buffer defined for each paging group and per each defined CCCH group. The buffer is organized according the FIFO principle.(see next section) The maximum length of one paging group buffer (see PAG_Q parameter definition in section 4.5) shall take into account the constraints of the MSC repetition (see T3113 MSC timer definition in section 4.4). It is recommended to set T_PAG parameter (see section 4.5) to a value smaller than T3113. Remark:
in this release, there is no autonomous repetition of the Paging messages performed by the BSS.
} The maximum number of all PAGING REQUEST messages, that can be stored in the BTS for one CCCH group is limited to the parameter PG_FULL (see section 4.5). If the buffer is full, or the maximum number of messages is reached, the next incoming PAGING COMMAND message is discarded and a performance management counter is incremented (see section 3.4). Ed 03 3BK 11202 0051 DSZZA
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With the PAGING COMMAND messages received from the BSC, the BTS (FUCO) builds PAGING REQUEST messages. The PAGING COMMAND contains two main parameters: Paging Group and Mobile Identity (IMSI or TMSI). On the radio interface, 3 different messages (PAGING REQUEST TYPE 1, 2 or 3) can be sent according to the number of Mobile Stations with the same Paging Group and CCCH group to be paged and also according to the type(IMSI or TMSI) of the Mobile Identity. The algorithm to build a PAGING REQUEST message is as follows : Following combinations are possible for each type of paging request message: TYPE 1 IMSI TMSI IMSI,TMSI IMSI,IMSI TMSI,TMSI
TYPE 2 TMSI,TMSI,TMSI
TYPE 3 TMSI,TMSI,TMSI, TMSI
TMSI,TMSI,IMSI
In the order of arrival of the PAGING COMMAND message of the same paging group, a PAGING REQUEST TYPE message is generated. If it isn't possible to rebuild the PAGING REQUESTmessage because the message is already full (IMSI/IMSI, TMSI/TMSI/IMSI or TMSI/TMSI/TMSI/TMSI) or if it is not possible to merge the next PAGING COMMAND message in this PAGING REQUEST message ,the message is put in state 'message ready' (MR) and a new one is built. The RTS(Request To Send) event from L1 is time critical due to its real time constraint therefore it is given a higher process priority, than to optimize the content of the PAGING REQUEST message The mapping of logical to physical channels should be done as follows : The required 51 TDMA multiframe occurs, when PAGING_GROUP div (N div BS_PA_MFRMS) = (FN div 51) mod (BS_PA_MFRMS) The PCH channel on each CCCH is divided into blocks. An index calculation which is used to gain access to the appropriate paging block is given below. This paging index is used to access the table shown in 05.02 section 7 table 5 to obtain the actual paging block. Paging block index = PAGING_GROUP mod (N div BS_PA_MFRMS) 3a RTS event for paging group 1 occurs. PAGING REQUEST TYPE 1 with 2 Mobile Identities is transmitted. 3b same as above, but for paging group 2 and PAGING REQUEST TYPE 2 with 3 Mobile Identities 3d same as above, but for paging group 3 and PAGING REQUEST TYPE 3 with 4 Mobile Identities(TMSIs)
3c If no paging message is pending, a paging filling frame is transmitted. The paging filling frame consists of a PAGING REQUEST TYPE 1 message with: * length of mobile identity contents : 1 * Identity digit 1 : 0000 * odd/even indic :0 Ed 03 3BK 11202 0051 DSZZA
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* Type of identity
: 0 = no Identity
3.3.2 Paging queues Within the BTS, all the available Paging Groups are represented by FIFOs (this does not constrain implementation). There is one FIFO available per Paging Group (up to 81 FIFOs per CCCH Group). The FIFOs are initialized at every configuration time when receiving the SYSTEM INFORMATION TYPE 3 with parameters modification. It means that pending PAGING REQUEST messages are lost when a new configuration is set. All the messages stored in one queue are delivered to the Mobile Station when the TDMA frame constitution allows the transmission of the Paging Group associated to the paging queue. This takes place within the 51 multiframe for which the following condition is met :
PAGING_GROUP div (N div BS_PA_MFRMS) = (FN div 51) mod BS_PA _MFRMS
Then, the index to the required paging block of the available blocks in the 51 multiframe is given by the formula :
Paging block index = PAGING_GROUP mod (N div BS_PA_MRFMS)
All the messages received from the BSC (the "PAGING COMMAND" messages) are stored in one queue according to the Paging Group and the CCCH slot number. An algorithm manages the storage of incoming PAGING COMMAND messages into PAGING REQUEST messages. The principle is to complete, if possible, a pending PAGING REQUEST message (which enables up to 4 MSs to be paged at the same time). This algorithm is presented in the previous section. Note : The FN value is broadcast over the BCCH channel in TDMA frame called Synchronisation Burst (SCH).
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3.3.3 Access Grant Procedure The following, describes the detailed behaviour within the BTS. The given number refers to the steps as indicated on the left side of the scenario in section 3.1.2 . 1: After the MS has transmitted the CHANNEL REQUEST message, it starts the timer T3120 (GSM phase 1 MS) or waits for a randomly drawn number of RACH slots (GSM phase 2 MS) as described in phase 2 GSM technical specification 04.08. The timer is calculated according following formula: T3120 = T1 + T_Random T1 is set to: - for a phase 1 MS : - for a phase 2 MS : value.
* 250 ms in case of non combined CCCH * 350 ms in case of combined CCCH/SDCCH * Refer to phase 2 GSM 04.08 [2], the value differs following Tx-integer
T_Random is set to a random value n which gives the number of RACH timeslots between he T1 expiry and the end of the period T3120 (n = 0 ... Tx-integer (range:3-50) - 1). If the MS does not receive an IMMEDIATE ASSIGNMENT on the AGCH within T3120, it will repeat the CHANNEL REQUEST message as long as it was indicated with the Max-retrans parameter. After the last CHANNEL REQUEST sending, the MS waits a response from the network during T3126 As well Tx-integer and Max-retrans are elements within the RACH control parameter IE, the MS had received in the SYSTEM INFORMATION TYPE 1, 2, 3 or 4 messages. After the correct decoding of a CHANNEL REQUEST message, the BTS generates the CHANNEL REQUIRED message with : * Channel number IE: - timeslot(TN), on which the message was received (0,2,4,6). * the Request reference IE: - absolute frame number modulo 42432 on which the CHANNEL REQUEST message was received, - random reference generated by the MS, and sent in the CHANNEL REQUEST message * Timing advance IE: - measured delay between begin of the RACH timeslot which carries that CHANNEL REQUEST message and the receipt of the Access Burst. 3-4: SDCCH allocation procedure, refer to [11]. 5: IMMEDIATE ASSIGN COMMAND is received from the BSC. The BTS generates the corresponding Air Interface message IMMEDIATE ASSIGNMENT. The message has to be transmitted on that radio timeslot (0,2,4,6), as it was indicated by the Channel number IE.
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6: As the transmission from BSC is not time synchronous with the transmission on the Air Interface, the already generated IMMEDIATE ASSIGNMENT message has to be buffered, until a RTS event from L1 is received. More than 1 message can be stored in this AGCH-queue. If the queue has not reached its maximum number of queue entries, then dequeuing is done with the FIFO principle. After receiving the RTS event, the message is put on the AGCH of the CCCH. If the AGCH buffer is empty(no pending IMMEDIATE ASSIGNMENT), then a LAPDm - Fill frame (see TS GSM 04.06 [1]) has to be sent. The number of AGCHs per CCCH multiframe is defined by the system parameter BS_AG_BLKS_RES (range : 0 -7) which was also sent with the SYSTEM INFORMATION TYPE 3 message to the MS. The number of IMMEDIATE ASSIGNMENT messages in the AGCH-queue should not exceed AG_Q. Parameter definition and calculation is defined in section 4.5. If the AGCH-buffer is full, the new request is put on the last position of the queue, the oldest request in the queue is deleted and a performance measurement counter is incremented (see section 6). If no AGCH is reserved (BS_AG_BLKS_RES=0), the BTS has to send IMMEDIATE ASSIGNMENT messages over PCH blocks. Each time an IMMEDIATE ASSIGNMENT message must be sent to a mobile (a message is in the AGCH queue), it is sent in a PCH block (as in this case all CCCH are PCH). Therefore IMMEDIATE ASSIGNMENT messages have higher priority than PAGING REQUEST messages.
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3.4 TELECOM AND O&M INTERWORKING WITHIN THE BSS 3.4.1 Configuration Management The following table shows all the system parameters within a BSS which have an influence on the paging and access grant procedure and the affected tasks, if they are modified. System-Parameter CCCH_CONF
IE/ SYS INFO TYP Control Chl. descr./ SYS INFO TYP 3
BS_AG_BLKS_RES
Control Chl. descr./ SYS INFO TYP 3
BS_PA_MFRMS
Control Chl. descr./ SYS INFO TYP 3
Max retrans
RACH-controlparameter/ SYS INFO TYP1,2,3,4 RACH-controlparameter/ SYS INFO TYP1,2,3,4
Tx integer
meaning of the parameter num. of Physical chls. used for CCCH: 1 chl comb. with SDCCH, 1,2,3, or 4 chls not comb. with SDCCH, num. of reserved AGCH within a CCCH multiframe period in num. of multiframes of a pag-group repetition num. of random access attempts of the MS used to calculate a random access value for T3120
task see note 1,
see note 1,
see note 1,
see note 2 doesn't interrupt the paging/access-grant process see note 2 doesn't interrupt the paging/access-grant process
note 1: The change of these parameters has a great impact on OMC/BSC/BTS(FUCO,OMU). This is described in ref [11]. The main influence for the paging/access grant-process is: * during reconfiguration, the PCH queues are emptied and new Paging Command messages are discarded until reconfiguration is completed. * Immediate Assignment messages are discarded during reconfiguration, but only if the CCCH_CONF is modified. note 2: This parameter is transparent for the BSS, but has an influence on the performance of the paging/access grant procedure.
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3.4.2 Performance Management See the section about future improvements. Another kind of measurement is done by counting the number of paging buffers which are free for the paging queues associated with its CCCH. B = (GS - BS) * N_Pag_msg B = Free Buffer space of one CCCH timeslot. GS = Global Space of all paging buffers of one CCCH timeslot. BS = number of pending Paging Requests of one CCCH timeslot. N_Pag_msg = number of paged MS's within one Paging Request message - set to 4, as the most expected identifiers will be TMSIs. This snapshot value is sent within the CCCH LOAD INDICATION message from the BTS to the BSC. The BSC does not perform any tasks on receipt of this message and the message is discarded. The CCCH LOAD INDICATION message contains also the RACH load information element. This message is only sent if a certain RACH load is reached (THR_CCCH_LOAD). After matching of this threshold, there is a guard time until the next transmission of this message (but only if the threshold is reached again).
3.4.3 Error Reporting On the Abis interface : The BTS will send the ERROR REPORT message to the BSC with the cause 'Invalid Information element content' if the PAGING COMMAND or the IMMEDIATE ASSIGN COMMAND is found semantically wrong. The BSC will not perform any specific task, when receiving that message with the above cause value.
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4. INTERFACE DESCRIPTION 4.1 GSM INTERFACES/PHYSICAL INTERFACES 4.1.1 A Interface PAGING - Message type - IMSI - TMSI - Cell Identifier list - Channel needed (1) (2)
(3)
optional (1) optional (2) optional (3)
If IE is present, paging to the MS is performed with the TMSI. If this IE is not present, paging is performed on all cells, regardless if it is a multicell BSS or not. For GSM phase 2, this IE is mandatory but it remains optional for the release 4 implementation. This IE is always ignored by the BSS.
For details on the message format please see [8]. Restriction: If the CGI coding is used in the cell identifier list, a maximum of 30 cells can be included in the message. The service of segmentation is not offered by the BSS implementation of the SCCP on the A interface.
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4.1.2 Abis Interface PAGING COMMAND - Message discriminator - Message type - Channel Number - Paging Group - MS Identity - Channel needed (1) (1)
Not sent by the BSC
IMMEDIATE ASSIGN COMMAND - Message discriminator - Message type - Imm. Assign Info (1) (1)
This IE contains a complete IMMEDIATE ASSIGNMENT as defined in the Air interface section, it is completely transparent for the BTS.
CCCH LOAD INDICATION - Message discriminator - Message type - RACH Load (1) - Paging Load (1) (1)
The two IEs are always present in the message, they are not considered as conditional elements following the channel number. The channel number IE indicates 'uplink CCCH'. Note: The message is discarded within the BSC.
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4.1.3 Air Interface Each time it is used, the L2 pseudo length is equal to ( 23 (length of a layer 2 frame) - length of the 'Rest octets' IE - 1 (length of this IE) ) or is equal to the sum of lengths of all the IEs except 'Rest octet' IE and this IE.
PAGING REQUEST TYPE 1 - L2 pseudo length - message header (Protocol discriminator/ Skip indicator/Message type) - Page mode (1) - Channel needed (3) - Mobile identity (2) - Mobile identity optional (2) - P1 rest octets (1) (2) (3)
only 'normal paging' IMSI or TMSI in case of 2 TMSIs this msg is also sent. It is always set to 'any channel'. These bits are spare bits for Phase 1 mobiles.
PAGING REQUEST TYPE 2 - L2 pseudo length - message header - Page mode - Channel needed - TMSI - TMSI - Mobile identity - P2 rest octets
(1) (3) optional (2)
(1) only 'normal paging' (2) TMSI or IMSI, this message is only sent with 3 mobile station Identities, therefore this element is always present. (3) It is always set to 'any channel'. These bits are spare bits for phase 1 mobiles. PAGING REQUEST TYPE 3 - L2 pseudo length - message header - Page mode - Channel needed - TMSI - TMSI - TMSI - TMSI - P3 rest octets (1) (2)
(1) (2)
only 'normal paging' It is always set to 'any channel'. These bits are spare bits for GSM phase 1 mobiles.
IMMEDIATE ASSIGNMENT
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- L2 pseudo length - page mode - channel description - request reference - timing advance - mobile allocation - starting time - IA rest octets (1) (2) (3) (4)
(1)
(2) optional (3) (4)
' same as before' is used in the case of fixed frequency, the length indication is set to 0. this IE is not sent This IE contains the frequency parameters, before time and is used for frequency redefinition for GSM phase 2 mobiles. It is not filled in this release.
4.2 INTERNAL INTERFACES 4.3 EXTERNAL INTERFACES 4.4 TIMERS LIST T3113 : started in the MSC after sending of PAGING and stopped after the receipt of PAGING RESPONSE T3101 : timer used to monitor the seizure of the channel by the MS and the completion of the immediate assignment procedure T3120 : MS timer used to monitor the reception of IMMEDIATE ASSIGNMENT message. This timer name has been removed from GSM phase 2 TS. T3126 : MS timer indicating the waiting time after sending the last CHANNEL REQUEST. This timer name is newly defined by GSM phase 2 TS.
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4.5 PARAMETERS LIST BS_CC_CHANS : number of CCCH timeslots (range : 1 - 4) CCCH_CONF :
CCCH configuration, which shows the number of physical channels combined or not with SDCCH (binary representation with 3 Bits, see table below).
The following table shows the relationship between BS_CC_CHANS and CCCH_CONF.
BS_CC_CHANS 1 1 2 3 4
CCCH_CONF 000 001 010 100 110
1 basic 1 basic 2 basic 3 basic 4 basic
physical physical physical physical physical
Remark channel.- not combined with SDCCH channel.- combined with SDCCH channel.- not combined with SDCCH channel.- not combined with SDCCH channel.- not combined with SDCCH
Note: The three last lines are not allowed to be used in this release. BS_AG_BLKS_RES : number of reserved AGCHs per CCCH multi-frame (range : 0 - 7). This depends on the size of the location areas (big location areas will force more paging attempts than small ones) and the expected traffic (mobile originating/terminating calls). If a CBCH is defined for a cell and is supported by a SDCCH/8 timeslot, BS_AG_BLKS_RES shall be set to 1 or greater (see [8]). BS_PA_MFRMS : number of CCCH-multiframes, when the occurence of a specific paging group is repeated (range : 2 - 9). The power consumption of the MS in idle state is reciprocal to the value of BS_PA_MFRMS. AG_Q : maximum number of IMMEDIATE ASSIGNMENT messages in the AGCH queue per CCCH group. This maximum length is calculated according following formula : if BS_AG_BLKS_RES <> 0 then AG_Q = INT [(T3101 - 0.5s) * BS_AG_BLKS_RES / tmf]. if this formula gives zero or a negative value, then AG_Q = 1. if BS_AG_BLKS_RES = 0 then AG_Q = 12 (hardcoded value). AG_FULL : maximum value permitted for the parameter AG_Q. PAG_Q : maximum number of PAGING REQUEST messages that may be stored on one single queue per CCCH group.
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Following paragraph is applicable only to Release 4 sub-releases NOT including CR 015147 (see ref [14] for details) { PAG_Q value is calculated with following formula : PAG_Q = INT [T_PAG / (tmf * BS_PA_MFRMS)].
tmf = 235.38 ms (duration of one CCCH multiframe). BS_PA_MFRMS : number of multi frames used to carry CCCH blocks; range 2 to 9. PAG_Q(min) = 1 PG_FULL : maximum number of all PAGING REQUEST messages that can be stored in the BTS per CCCH group. } Following paragraph is applicable only to Release 4 sub-releases including CR 015147 (see ref [14] for details) { PAG_Q value is calculated with following formula : PAG_Q = INT [T_PAG / (tmf * BS_PA_MFRMS)] T_PAG : maximum time, a Paging message can be queued in the BTS before transmission on the Air Interface. tmf = 235.38 ms (duration of one CCCH multiframe). BS_PA_MFRMS : number of multi frame used to carry CCCH blocks; range 2 to 9. PAG_Q(min) = 1 PG_FULL : maximum number of all PAGING REQUEST messages that can be stored in the BTS per CCCH group. }
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