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ITCF parameterNUMBER OF IGNORED TRANSCODER FAILURE (ITCF)

This Parameter is used to check how many Transcoder Failure the systemwill receive before it Releases the calls.

Explanation:

 After a speech path connection has been established between the BTS and the TC,they try to align with each other to enable speech coding both in uplink and downlinkdirections. If the alignment procedure fails, speech decoding also fails and speech isno longer audible. In this case, the BTS sends CONNECTION_FAILURE_INDICATIONmessage to the BSC. The BSC requests for a clearing and then releases the resourcesconnected to the call. The cause field in this failure indication message is "REMOTETRANSCODER FAIL” 

When more aggressive HR is introduced, due to the interference in the air interfaceand signaling messages can be lost. Re-sending the messages one or more times canlengthen the call establishment dramatically and this might lead to trigger of REMOTETRANSCODE FAIL counters.

If parameter ITCF is set to 0 (default), the call clearing procedure will be triggeredimmediately when CONNECTION_FAILURE_INDICATION message (with causetranscoder failure) is received from BTS. Otherwise, BSC will not release the ongoingcall until the number of CONNECTION_FAILURE_INDICATION messages (with causetranscoder failure) received exceeds ITCF. BTS repeats the message at one-secondintervals. If the frame synchronization is obtained again or the call is released, thecounting of remote transcoder failure causes begins from zero again.

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ITCF parameter

 Advantage & Disadvantage if ITCF

[ ITCF=4 ]

• If the circuit is really faulty the call will be released after the BSC receives the fourCONNECTION_FAILURE_INDICATION message from the TC. So in this case call willcontinue on the Time slot for some time ( till 4 messages are not received) even if theBSC knows that the circuit is faulty.

• Secondly if the circuit is affected by a short term disturbance ( eg. short termtransmission disturbance) which causes a loss of TRAU frame synchronization the callwill NOT be released by the system.

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ITCF parameter

ITCF testing results on Mumbai Network

Settings in all the BSCs, ITCF = 0 On 13/02/06 ITCF settings were changed to 2 for all BSC in Mumbai Network.

Observation: Drop in no of Tr_Fail and Tch drop have improved.

Nokia Recommend to change the settings to 2 on all BSCs where we have aggressive HR.

Reduced Tr_Fail

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

    2    /    6    /    2    0

    0    6

    2    /    7    /    2    0

    0    6

    2    /    8    /    2    0

    0    6

    2    /    9    /    2    0

    0    6

    2    /   1    0    /    2    0    0

    6

    2    /   1   1    /    2    0    0

    6

    2    /   1    2    /    2    0    0

    6

    2    /   1    3    /    2    0    0

    6

    2    /   1   4    /    2    0    0

    6

    2    /   1    5    /    2    0    0

    6

    2    /   1    6    /    2    0    0

    6

Date

    N   o .   o

    f    T   r   a   n   s   c   o    d   e   r    F   a    i    l   u   r   e   s

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Date BSC

Tch

drp 

tr_

fail  BSC

Tch_

drp 

tr_

fail  BSC

Tch_

drp 

tr_

fail  BSC

Tch_

drp 

tr_

fail 

04/02/2006  BSC33KRT  1.20  1923  BSC29SPT  0.93  217  BSC28SLA  0.96  917  BSC31TRI  1.14  806 

05/02/2006  BSC33KRT  1.21  2063  BSC29SPT  0.90  312  BSC28SLA  0.75  116  BSC31TRI  1.01  873 

06/02/2006  BSC33KRT  1.30  2314  BSC29SPT  0.93  266  BSC28SLA  1.03  862  BSC31TRI  1.11  857 

07/02/2006  BSC33KRT  1.22  2431  BSC29SPT  0.93  543  BSC28SLA  0.95  1360  BSC31TRI  1.25  1148 

08/02/2006  BSC33KRT  1.29  3684  BSC29SPT  0.93  314  BSC28SLA  0.85  860  BSC31TRI  1.24  778 

09/02/2006  BSC33KRT  1.23  3263  BSC29SPT  0.93  492  BSC28SLA  0.78  452  BSC31TRI  1.10  899 

10/02/2006  BSC33KRT  1.04  1603  BSC29SPT  0.93  368  BSC28SLA  0.82  1055  BSC31TRI  1.10  1430 

11/02/2006  BSC33KRT  0.95  605  BSC29SPT  0.88  424  BSC28SLA  0.79  312  BSC31TRI  1.16  715 

12/02/2006  BSC33KRT  1.00  572  BSC29SPT  0.86  327  BSC28SLA  0.66  45  BSC31TRI  0.93  666 

13/02/2006  BSC33KRT  0.96  519  BSC29SPT  0.89  48  BSC28SLA  0.82  248  BSC31TRI  1.12  102 

14/02/2006  BSC33KRT  1.05  520  BSC29SPT  0.95  27  BSC28SLA  0.89  34  BSC31TRI  1.15  18 

15/02/2006  BSC33KRT  0.98  481  BSC29SPT  0.89  15  BSC28SLA  0.81  26  BSC31TRI  1.07  85 

16/02/2006  BSC33KRT  0.90  9  BSC29SPT  0.85  11  BSC28SLA  0.78  19  BSC31TRI  1.04  17