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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2G/GSM. Immediate Assignement is the answering message to the initial "Channel Request" explained above. This is to say to MS "OK, I will accept your 'channel request' and here goes the radio resource you can use for the following steps". One of the Channel Request example would be as follows. The most important thing you have to notice is that ...
- MS supports GSM HR (TSPC_AddInfo_HalfRate) ... After the reception of IMMEDIATE ASSIGNMENT REJECT, the MS shall not transmit during the time indicated in the "Wait Indication" field of the IMMEDIATE ASSIGNMENT REJECT message, and then it shall answer to the new paging requests. 2. After an assignment rejection, the MS shall perform a cell ...
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 ...
Immediate Assignment : 4. UE -> NW. Attach Request : 5. UE <- NW. Attach Reject (Cause #17) 1st Reject: 6. UE -> NW. Channel Request/Handover Access : 7. UE <- NW. Immediate Assignment : 8. ... GSM A-I/F DTAP - Attach Reject. Protocol Discriminator: GPRS mobility management messages .... 1000 = Protocol discriminator: GPRS mobility management ...
GSM radio frequency optimization (GSM RF optimisation) ... BSS in response to the received "channel request", will process it and immediately assign the MS a SDCCH (immediate assignment / assignment reject; done over AGCH). MS Paging response- After receiving the immediate assignment command, MS switches to the assigned "SDCCH" and transmits a ...
Support > Knowledge Base > GSM-R > Controller > BSC6000. ... Consequently, the BSC directly delivers an immediate assignment reject command, as shown in the following figure. The above analysis indicates that congestion in some cells is caused by a large number of channel requests initiated within an extremely short period, causing all SDCCHs ...
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.
Guest. Hello, immediate assignment reject is caused by sdcch congestion : if no SDCCH resource is availble in the BTS, the BSC sends an immediate assignment reject. Can you give, at the busy hour, the following QOS indicators: 1. nb of SDCCH requests. distribution of types of sdcch requests (loc upd, ms orig, ms term, sms, etc.)
immediate assignment message contains the assignment information of one MS. According to GSM specifications, MS must identity the immediate assignment (extended) information for the last three channel requests. If there is no channel to activate, BSC will send an immediate assignment reject or immediate assignment extended reject message to MS.
The IMMEDIATE ASSIGNMENT REJECT will indicate the value for the timer T3122. At the MS side, the timer T3122 will start and when this timer expires, the MS will makes another attempt for location updating. ... There is no default value specified by the GSM recommendation for this timer, and I think it is depended on the hardware vendor. In the ...
The paper discusses congestion relief using immediate assignment on the TCH (traffic channel). The impact of various immediate assignment strategies and their implementation in a live network are discussed. The impact of CBCH and alleviation of the resulting congestion by immediate assignment have been computed. The effect of paging load is discussed. The impact of immediate assignment on SMS ...
The rejection is immediate. But the BSC might or might not send the rejection message to the MS. (this is a parameter called "immediate assignment reject") if reject is not sent, the MS will just wait for a very short while, and send again another channel request. The delay between 2 consecutive channel requests is very short.
RR : Immediate Assignment . Immediate Assignement is the answering message to the initial "Channel Request" explained above. This is to say to MS "OK, I will accept your 'channel request' and here goes the radio resource you can use for the following steps". One of the Channel Request example would be as follows.
GSM Layer 3 (GSM L3) is defined in GSM 04.08. GSM L3 includes messages that are transmitted over the Common Control Channels. These are: BCCH information (System information messages) PAGCH messages (Immediate assignments) RACH accesses. CCCH messages are useful mainly for the purpose of verifying correct channel allocation through the logging ...
If no dedicated channel is available for assignment, the BTS can instead respond with the RR Immediate Assignment Reject message, which is similarly addressed and contains a hold-off time for the next access attempt. ... Performance Evaluation of Operational GSM's Air-Interface (Um). in Proc. of Applied Telecommunication Symposium, pp. 62-65 ...
On the AGCH, the network sends the RR Immediate Assignment message (GSM 04.08 Section 9.1.18) for a dedicated channel, usually an SDCCH. ... If the RACH burst of step 2 is not answered with an assignment or assignment reject in step 3 within a given timeout period ,usually on the order of 0.5 second, the handset will repeat step 2 after a small ...
Type: Secondary DNS Server IP Address (131) Length: 6. Secondary DNS Address: 192.168.1.2 (192.168.1.2) < Examples of Immdiate Assignment during IP traffic >. DLT: 147, Payload: gsm_a_ccch (GSM CCCH) GSM CCCH - Immediate Assignment. L2 Pseudo Length. 0010 11.. = L2 Pseudo Length value: 11. Protocol Discriminator: Radio Resources Management ...
The recommended value is 10s. III. Configuration and Influence The value of T3122 is included in the immediate assignment reject message. After the MS receives the immediate assignment reject message (no channels for signaling, A interface failure, overload of central processing unit, namely, CPU), it can send new trial calling request after T3122.
Value. T100 RADIO-LINK-TIMEOUT. Detects the presence of the radio link by detecting SACCH frames every 480 ms. 2 SACCH multiframes. That is 0.96 seconds if the SACCH is completely absent. T200 Data link timer. Used for re-transmission on the data link. The value varies depending on the message type. 155 ms for FACCH.
The USF, or Uplink State Flag, allows the multiplexing of several MS onto a single uplink PDTCH. The USF value is sent to the mobile station in a Packet Immediate Assignment message. The USF is also sent in Packet Uplink Assignment and Packet Timeslot Reconfigure messages. You can determine how well the mobile station reallocates its ...
On expiry of timer T3130 for the third time a rejection of the uplink request is indicated to the upper layers. The value of this timer is set to 5 seconds. T3142 The timer is used during packet access on CCCH and during packet access while in dedicated mode. It is started after the receipt of an IMMEDIATE ASSIGNMENT REJECT or a DTM REJECT message.
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.
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