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electron
2009-06-24, 05:26 PM
Hi all ,


What is the reason of Immediate Assignment failure in idle mode?

Dashty
2009-06-24, 05:41 PM
Dear,
Reasons below:
- SDCCH Congestion
- Phantom or dummy RACH,
- H/W (TRX, Combiner, diplexers, VSWR)
- Radio (Coverage, Interference, DL/UL unbalance, ...)

I hope can help,

Regards

ghassen
2009-06-24, 08:09 PM
also we have expired timers and co bcch and co bsic === phantom rach
(T10 < T_MSRFPCI),
FR call: (T_MSRFPCI Expiry)
FR call: (T10 Expiry)
Unsuccessful TCH assignment procedure LAPDm I-Frame
with ASSIGNMENT COMMAND not acknowledged by MS
(T200 Expiry), FR call

RF engineer
2009-06-24, 08:43 PM
Totally all the mentioned reasons posted are causes and if you want to be sure why you have this fail it is beteer to check what the requirement for channel request(MOC,MTC,location update,ememrgency,,,,,,,) ao when you find your request is high for one of them you can understand what is causes.
BR
RF

electron
2009-06-25, 02:43 AM
Dear friend thanks for your help

Finally i found the problem!

Problem was in radio link LOS!! after radio realignment problem solved



Regards

ghassen
2009-06-25, 03:06 AM
Dear friend thanks for your help

Finally i found the problem!

Problem was in radio link LOS!! after radio realignment problem solved



Regards

then it was T_MSRFPCI counter EXPIRED???

electron
2009-06-25, 12:45 PM
then it was T_MSRFPCI counter EXPIRED???

N200 Expired !

justdream
2010-02-22, 06:53 PM
Friends, can you give me some information about Phantom RACH
and how to optimize it?

RF engineer
2010-02-22, 07:27 PM
Friends, can you give me some information about Phantom RACH
and how to optimize it?
Phantom RACH is kind of non real channel request some time BTS decode noise as channel request and you can reduce it by change Parameter related to RACH and RX leve access min or RACH access min
BR
RF

justdream
2010-02-22, 07:29 PM
Phantom RACH is kind of non real channel request some time BTS decode noise as channel request
BR
RF

Thanks but in this way, can subcounters count the total number of Phantom RACH :confused:

RF engineer
2010-02-22, 11:12 PM
Thanks but in this way, can subcounters count the total number of Phantom RACH :confused:
Yes some vendor have this raw data and they took in to KPI formulation for immediate assignment but for me in huawei this KPI is not exist , make downtilt or change radio parameter as mentioned before the problem will be solved
BR
RF

justdream
2010-02-26, 01:48 AM
Experts,

can you give me the formula required to calculate the total number of phantom RACCH UL

My vendor is Siemens, kindly help :hug:

emahmoud
2010-02-26, 06:05 AM
Hi all ,


What is the reason of Immediate Assignment failure in idle mode?




Dear,

i think the problem related to 2 main causes:

1. interference: try out of band on BCCH TRX.
2. TMU HW Failure: Replace it.

viswajeet
2010-02-28, 09:38 PM
1. no agch available , full
2. agch message time out

transmission ok ? radio quality good ? if using sattelite need longer timer.

:hug: :hug: :hug:

radio_network
2010-02-28, 10:27 PM
what are all the other statistics to be affected due to phantom rach.

parsarka
2010-03-01, 03:46 AM
Yes some vendor have this raw data and they took in to KPI formulation for immediate assignment but for me in huawei this KPI is not exist , make downtilt or change radio parameter as mentioned before the problem will be solved
BR
RF

Hi,
Thanks for the vaulable suggestion.Please do the needfull to mention the entire parametrs & their optimal valuse to be used for Huawei system so that my network can be benifited.

Regards
Raj

RF engineer
2010-03-01, 05:30 PM
Hi,
Thanks for the vaulable suggestion.Please do the needfull to mention the entire parametrs & their optimal valuse to be used for Huawei system so that my network can be benifited.

Regards
Raj
Rx level access min -102, RACH min access level -105 what BSC you are using it .
BR
RF

viswajeet
2010-03-03, 03:12 AM
Experts,

can you give me the formula required to calculate the total number of phantom RACCH UL

My vendor is Siemens, kindly help :hug:

hi justdream,
UL Phantom RACH ? hmm.. houw bout maxretrans ?

jox101
2010-03-17, 05:42 PM
Hi!

Anyone here knows the difference between rach access min level and rx access min level?

bruno hautenfaust
2010-04-06, 12:08 PM
The counter for Number of Immediate Assignment Attempts is ImmAssAtt = ATIMASCA[1 ..14] also you can find
MBUSYSSP[6] :Receipt of a invalid ESTABLISHMENT INDICATION message (undefined Layer3
message) related for a SDCCH (BTS → BSC) or no receipt of an ESTABLISHMENT
INDICATION message after activation of a SDCCH (phantom RACH).

BR

danikd
2010-05-05, 05:01 PM
Friends, can you give me some information about Phantom RACH
and how to optimize it?

Phantom RACH is a process when specific mobile is sending Random Access burst to a serving cell (cell which specific mobile is camping on). The Random Access burst contains TSC (Training Sequence) the TSC is derived from BCC number which is part of BSIC transmitted on Synchronization Channel (SCH) on BCCH TRX i.e. TSC=BCC for BCCH TRX.

Now when mobile transmits Random Access burst, this transmission is OMNI directional i.e. transmitted not only toward serving cell but to all surrounding cells as well.
When network utilizes a very tight BCCH reuse (less than 25 BCCH in use) in urban area, then the BCCH reused with in the limited geographical area many times and BCCH allocation requires proper allocation of BCC in order to prevent BCCH/BCC (not BSIC) reuse.

More over the Phantom RACH is related to UL performance of the cell. The UL performance of the cell is 100% depends on antenna configuration i.e. antenna type and tilt. Correctly designed antenna configuration will prevent appearance of Phantom RACH as well.

If you would like to know more...just ask!!!!

Nasrin
2010-09-12, 01:08 AM
hi all
phantom RACH can degrade imm ass fail on sdcch ,what about sd drop?can affect it ? other qusetion when HLR check the channel requset is from MS or not?

RF Engr
2010-09-29, 10:02 PM
Phantom RACH is a process when specific mobile is sending Random Access burst to a serving cell (cell which specific mobile is camping on). The Random Access burst contains TSC (Training Sequence) the TSC is derived from BCC number which is part of BSIC transmitted on Synchronization Channel (SCH) on BCCH TRX i.e. TSC=BCC for BCCH TRX.

Now when mobile transmits Random Access burst, this transmission is OMNI directional i.e. transmitted not only toward serving cell but to all surrounding cells as well.
When network utilizes a very tight BCCH reuse (less than 25 BCCH in use) in urban area, then the BCCH reused with in the limited geographical area many times and BCCH allocation requires proper allocation of BCC in order to prevent BCCH/BCC (not BSIC) reuse.

More over the Phantom RACH is related to UL performance of the cell. The UL performance of the cell is 100% depends on antenna configuration i.e. antenna type and tilt. Correctly designed antenna configuration will prevent appearance of Phantom RACH as well.

If you would like to know more...just ask!!!!
Its a great reply.But dont you think interference on uplink can also cause Phantom rach e.g external interference in network causing phantom rach

danikd
2010-10-03, 06:17 PM
Its a great reply.But dont you think interference on uplink can also cause Phantom rach e.g external interference in network causing phantom rach

As far as I understand, you are referring to non-GSM signal source that transmits with in the UL GSM band on BCCH frequency?

If I understand you right, then the answer is following:

The probability that Non-GSM signal will introduce Phantom RACH effect is very low, since in order to be decoded on on BTS side it should be GMSK modulated and should contain Random Access message with Access Cause inside.

The external (non-GSM) interference you can recognize by analyzing the ICM (Idle Channel Measurements) statistics.

Some GSM vendors like E*******, Siemens, Huawei have an efficient features to monitor UL interference for entire band (similar to UMTS UL RTWP measurements).
Those features (their results) can be very helpful for external UL interference recognition and identification.

Best regards,

danikd
2010-10-03, 06:23 PM
hi all
phantom RACH can degrade imm ass fail on sdcch ,what about sd drop?can affect it ? other qusetion when HLR check the channel requset is from MS or not?

SDCCH drop could not be affected by Phantom RACH effect. Since SDCCH drop counted only after SDCCH assignment by specific mobile (immediate assignment complete and RRM - radio resource management engaged for specific connection). Just to remind Phantom RACH just initiates Immediate Assignment procedure but never competes it.

To be more precise - HLR never check channel request. All channel requests are managed on BSS level. HLR is involved only into Authentication procedure. This procedure is a DTAP procedure (Direct Transfer), where BSS side (air-interface, BTS, BSC) are transparent and not involved into transaction (they just used as transport pipe for message).

Best regards,

shup7
2011-03-31, 11:17 AM
Phantom RACH is kind of non real channel request some time BTS decode noise as channel request and you can reduce it by change Parameter related to RACH and RX leve access min or RACH access min
BR
RF



thank you for your detailed explain..