immediate assignment reject gsm

3GPP 44.018 GSM/EDGE Radio Resource Control (RRC) protocol Mobile radio interface Layer 3 specification Release 17 TS

This message is sent on the CCCH or encapsulated in the PACKET CS COMMAND message on the PACCH (see 3GPP TS 44.060) by the network to up to four mobile stations to indicate that no channel is available for assignment. See table 9.1.20.1. This message has L2 pseudo length 19.

Message type: IMMEDIATE ASSIGNMENT REJECT

Significance: dual

Direction: network to mobile station

Table 9.1.20.1: IMMEDIATE ASSIGNMENT REJECT message content

NOTE: Index 1 refers to the first mobile station, index 2 refers to the second MS and so on.

9.1.20.1 Use of the indexes

A request reference information element and the following wait indication information element refer to the same mobile station. So it is possible to reject up to four channel requests with this message.

9.1.20.2 Filling of the message

If necessary the request reference information element and the wait indication information element should be duplicated to fill the message.

9.1.20.2a Request Reference

When set to the value ‘0111 1111’, the RA information of the Request Reference i IE indicates that an Extended RA i field may be included in the IAR Rest Octets. The mobile station shall use the information in the Extended RA i field to identify the Immediate Assignment Reject message corresponding to an EGPRS Packet Channel Request message. If the Extended RA i field is not included, the mobile station shall assume that the Request Reference i IE does not correspond to the EGPRS Packet Channel Request message.

When the mobile station receives the IMMEDIATE ASSIGNMENT REJECT message encapsulated in the PACKET CS COMMAND message on the PACCH (see 3GPP TS 44.060), it shall ignore the contents of all the Request Reference i IEs and regard them as unnecessary IEs.

9.1.20.3 Wait Indication

When IMMEDIATE ASSIGNMENT REJECT message is for RR connection establisment then this IE contains timeout value for T3122. If IMMEDIATE ASSIGNMENT REJECT message is for TBF establisment for GPRS MS then this IE contain timeout value for T3142.

When the mobile station receives the IMMEDIATE ASSIGNMENT REJECT message encapsulated in the PACKET CS COMMAND message on the PACCH (see 3GPP TS 44.060), it shall ignore the contents of the Wait Indication 2, 3 and 4 IEs and regard them as unnecessary IEs.

9.1.20.4 IAR Rest Octets

The sum of the length of this IE and the L2 Pseudo Length of the message equals 22.

SDCCH congestion occurs

Issue description, handling process, suggestions.

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CSSR / TCH assignment / imm assignment

Hi guys. Do you have any useful document to One: explain TCH _ASSIGNMENT / IMM ASSIGNMEMT in clear way two: learn how we can optimize them

The IMMEDIATE ASSIGN message facilitates the assignment of the MS onto an SDCCH channel. Correspondingly, the IMMEDIATE ASSIGN REJECT message facilitates the refusal of the access. If the SDCCH reservation or activation fails, the BSC sends the IMMEDIATE ASSIGN REJECT message to the MS. The GSM timer T3101 supervises the immediate assignment procedure.

Successful TCH assignment indicates the procedure from the BSC receiving the Channel Request message sent by the MSC to receiving the Assignment Complete message.

So, in the case of Immediate Assignment, my recommendation is to monitor how many rejects occurs, and this is done by checking the counter related to Immediate Assignment Rejects which most of the times should be zero. If not, this indicates congestion in a very early stage of a call (for instance) since not even the SDCCH can be assigned. The cause of rejects needs to be analized but in a first and basic approach, sometimes it can be solved by downtiltting the antenna to eliminate far access, however. If the site has a satellite Abis there is a totally different approach. For more info please check on 3GPP TS 04.08.

Regarding TCH assignments, basically a failure means that the UE could not size a TCH, let´s say, for a call or HO, so, you need to find the reason causing this event which can be TCH congestion or blocking due to many reasons like, lack of resources (HW) or poor RF quality, so this analysis will lead you to other counters or KPIs that you will need to check.

For more info check 3GPP TS 04.08 and look for traffic channel assignment.

Congestion relief through immediate assignment in GSM and GPRS networks

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Timer Optimization in GSM networks

This is basically the brief description of the various timers used in GSM network and its optimization techniques..

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GSM Timers Mobile Side

This page covers timers used in GSM on mobile side which include T3110, T3112, T3114, T3122, T3128, T3130, T3142, T3148, T3164, T3204, T3206, T3208, T3210, T3220, T3222, T3224 and T3232.

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Home » Topics » Telecom Design » Immediate Assignment Problem

Immediate Assignment Problem

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Pls help to find the correct problem & solution:- Problem:-When doing the drive test MS A(Calling party)gets nothing(no alerting) but the MS B (called party) gets the miss call for a very short duration & same time TEMS shows blocked call (whereas layer 3 message shows “NO IMMEDIATE ASSIGNMENT” or “MISSING IMMEDIATE ASSIGNMENT” what does it mean. As cell is under utilized. For further more info pls….

Pls help Thanx in advance

the MS A could not get the immediate assignment. It means that the cell “A” suffers SDCCH Congestion. There is no other reason for cell A to not allocate a SDCCH channel. Check your qos Stats : SDCCH blocking or SDCCH Congestion.

You should activate the “Immediate assignment reject” feature, that will help increase the stats.

regards pix

Actually this feature is already been activated & also there is no SDCCH Blocking or SDCCH congestion.And from MSC side I am getting RAB assignment failure message.

Layer 3:- MS1 System Information Type 3

Time : 10:35:45.42 Vendor Header ARFCN : 594 (GSM 1800) L2 pseudo length : 18 Skip indicator : 0 Protocol discriminator : (6) Radio resources management messages Message type : 27 Cell identity (CI) : 13441 (Hex 0x3481) Location Area Identification Mobile country code (MCC) : 405 Mobile network code (MNC) : 027 Location area code (LAC) : 101 (Hex 0x0065) Control Channel Description MSCR : (1) MSC is Release ’99 onwards Attach/detach allowed (ATT) : (1) MSs in the cell shall apply IMSI attach and detach procedure BS-AG-BLKS-RES : 2 CCCH-CONF : (2) 2 basic physical channels used for CCCH, not combined with SDCCHs CBQ3 : (0) Iu mode not supported BS-PA-MFRMS : 2 multiframes period T3212 timeout value : (15) 1.5 hours Cell options (BCCH) Dynamic ARFCN mapping indicator (DN-IND) : (0) Dynamic ARFCN mapping is not used by the PLMN Power control indicator (PWRC) : (0) PWRC Not set DTX indicator : (1) The MSs shall use uplink discontinuous transmission RADIO-LINK-TIMEOUT : 44 Cell selection parameters CELL-RESELECT-HYSTERESIS : 14 dB Rxlev hysteresis for LA-reselection MS-TXPWR-MAX-CCH : 0 ADDITIONAL RESELECT PARAM IND (ACS) : (0) System information type 16 and 17 are not broadcast on the BCCH HALF RATE SUPPORT (NECI) : (0) New establishment causes are not supported RXLEV-ACCESS-MIN : 8 RACH control parameters Max retransmission : (2) Maximum 4 retransmissions Tx-integer : (12) 20 slots used Cell bar access : (0) Not barred Call reestablishment : (0) Allowed Access control Emergency Call allowed : (0) All MSs Barred classes : Rest Octets Selection Parameters cbq : 0 Cell reselection offset : (5) 10 dB Temporary offset : (1) 10 dB Penalty time : (0) 20 s System Information 2ter indicator – Not Available Early classmark sending control – Explicity accepted BCCH scheduling is not sent in SI9 GPRS indicator RA color : 0 SI13 position : (0) SI13 message is sent on BCCH Norm Neither UTRAN nor CDMA2000 classmark change message shall be sent with the Early classmark sending SI2QInd SI2 Quater Position : (0) SI2 quater message is sent on BCCH Norm

Message dump (Hex): 06 1B 34 81 04 75 20 00 65 D2 00 0F 1A E0 08 B0 00 00 85 20 00 0B

MS1 Time: 10:35:45.42

Blocked Call Block type: No Immediate Assignment

if there is no sdcch assignment and there is no sdcch congestion, then i would suspect a software problem…

let’s check qos stats:

1/ are there SDCCH assigments in the cell? 2/ what is the main cause of sdcch rejection ? 3/ what is the mean holding time of a sdcch channel? 4/ what is the state of your TCH Queuing? (are there MS queued?)

could you get an immediate assignment with another MS in this cell ? and with this TEMS MS in another cell ?

in your cell, there is the feature multiple CCCH activated. I don’t know if that can cause such problem, but it’s worth investigating.

Regards pix

Hi Pix, Thanx, The feature multiple CCCH is just activated as there is high ABIS_CCCH load.Another things that you have asked ‘ll let you know.

ok, can you also check the Abis RSL congestion ?

MS2 System Information Type 3

Time : 13:17:03.68 Vendor Header ARFCN : 80 (E-GSM) L2 pseudo length : 18 Skip indicator : 0 Protocol discriminator : (6) Radio resources management messages Message type : 27 Cell identity (CI) : 1752 (Hex 0x06D8) Location Area Identification Mobile country code (MCC) : 621 Mobile network code (MNC) : 30 Location area code (LAC) : 40624 (Hex 0x9EB0) Control Channel Description MSCR : (1) MSC is Release ’99 onwards Attach/detach allowed (ATT) : (1) MSs in the cell shall apply IMSI attach and detach procedure BS-AG-BLKS-RES : 1 CCCH-CONF : (0) 1 basic physical channel used for CCCH, not combined with SDCCHs CBQ3 : (0) Iu mode not supported BS-PA-MFRMS : 2 multiframes period T3212 timeout value : (20) 2.0 hours Cell options (BCCH) Dynamic ARFCN mapping indicator (DN-IND) : (0) Dynamic ARFCN mapping is not used by the PLMN Power control indicator (PWRC) : (1) PWRC Set DTX indicator : (1) The MSs shall use uplink discontinuous transmission RADIO-LINK-TIMEOUT : 4 Cell selection parameters CELL-RESELECT-HYSTERESIS : 14 dB Rxlev hysteresis for LA-reselection MS-TXPWR-MAX-CCH : 5 ADDITIONAL RESELECT PARAM IND (ACS) : (0) System information type 16 and 17 are not broadcast on the BCCH HALF RATE SUPPORT (NECI) : (1) New establishment causes are supported RXLEV-ACCESS-MIN : 13 RACH control parameters Max retransmission : (0) Maximum 1 retransmission Tx-integer : (14) 32 slots used Cell bar access : (0) Not barred Call reestablishment : (0) Allowed Access control Emergency Call allowed : (0) All MSs Barred classes : Rest Octets Selection Parameters cbq : 0 Cell reselection offset : (0) 0 dB Temporary offset : (0) 0 dB Penalty time : (0) 20 s System Information 2ter indicator – Not Available Early classmark sending control – Explicity accepted BCCH scheduling is not sent in SI9 GPRS indicator RA color : 0 SI13 position : (0) SI13 message is sent on BCCH Norm Neither UTRAN nor CDMA2000 classmark change message shall be sent with the Early classmark sending

Message dump (Hex): 06 1B 06 D8 26 F1 03 9E B0 C8 00 14 50 E5 4D 38 00 00 80 00 00 2B

At a distance of above 5km, am experiencing no immediate assignment. there are no near by sites to serve only far away site, there by serving cell is having bad rxlevel at the time a call is to be established. what kind of recommendation am i to quote? a new site to be built or increase of BTS power of the serving cell.

Could some one explain Establishment Cause=17: in Immediate Assignment and how we can control it

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GSM T3126 Vs T3122

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Thread: GSM T3126 Vs T3122

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Dears, When the MS receives an Immediate Assignment reject, it start two timers T3122 & T3126 could some one explain the difference and the relation between these two timers? does MS start a cell reselection when receiving the reject? B regards,

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Re: GSM T3126 Vs T3122

T3122: This timer is used during random access, after the receipt of an IMMEDIATE ASSIGN REJECT message. Its value is given by the network in the IMMEDIATE ASSIGN REJECT message. T3126:This timer is started either after sending the maximum allowed number of CHANNEL REQUEST messages during an immediate assignment procedure. Or on receipt of an IMMEDIATE ASSIGNMENT REJECT message, whichever occurs first. It is stopped at receipt of an IMMEDIATE ASSIGNMENTmessage, or an IMMEDIATE ASSIGNMENT EXTENDED message. At its expiry, the immediate assignment procedure is aborted. The minimum value of this timer is equal to the time taken by T+2S slots of the mobile station's RACH. S and T. The maximum value of this timer is 5 seconds Originally Posted by peanut Dears, When the MS receives an Immediate Assignment reject, it start two timers T3122 & T3126 could some one explain the difference and the relation between these two timers? does MS start a cell reselection when receiving the reject? B regards,

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