Huawei SDDCH Conversion

[engaom]

Dear Gents;

I have a question about the below conditions for the SDCCH conversion; what do these two conditions really mean?

This is mentioned in HEDEX RAN 13.0


b The BSC determines whether the number of idle TCHHs plus twice the number of TCHFs is greater than eight.
If yes, dynamic SDCCH conversion is allowed. Otherwise, the BSC proceeds with 6.c (http://localhost:7890/pages/GEA0328D/02/GEA0328D/02/resources/FPD/Dynamic%20Channel%20Conversion.htm#li_c)
c The BSC determines whether the number of idle TCHHs plus twice the number of TCHFs is greater than twice the number of TRXs in the cell.
If yes, dynamic SDCCH conversion is allowed. Otherwise, dynamic SDCCH conversion is not allowed.

Appreciate your feedback
Thanks

[yellowant2512]

Please provide full doc about this issue, so others can check and help you.

[Vladislav]

Dear Gents;

I have a question about the below conditions for the SDCCH conversion; what do these two conditions really mean?

This is mentioned in HEDEX RAN 13.0


b The BSC determines whether the number of idle TCHHs plus twice the number of TCHFs is greater than eight.
If yes, dynamic SDCCH conversion is allowed. Otherwise, the BSC proceeds with 6.c (http://localhost:7890/pages/GEA0328D/02/GEA0328D/02/resources/FPD/Dynamic%20Channel%20Conversion.htm#li_c)
c The BSC determines whether the number of idle TCHHs plus twice the number of TCHFs is greater than twice the number of TRXs in the cell.
If yes, dynamic SDCCH conversion is allowed. Otherwise, dynamic SDCCH conversion is not allowed.

Appreciate your feedback
Thanks

HI,
Due to Huawei documentation (HedEx R13) there are next tigers for the dyn SDCCH conversion:
IDLESDTHRES (Idle SDCCH Threshold N1) - hreshold of idle SDCCHs in a cell. When the number of idle SDCCHs in a cell is smaller than or equal to the threshold, the BSC attempts to convert available TCHs or dynamic PDCHs into SDCCHs.
This parameter is one of the conditions for the dynamic conversion of the TCHF or dynamic PDCH to the SDCCH. In addition to the condition that the number of idle SDCCHs should be smaller than or equal to IDLESDTHRES, the following three conditions must be met to trigger the conversion from the TCHF or dynamic PDCH to the SDCCH: 1. SDDYN in SET GCELLBASICPARA is set to YES. 2. In a cell, the value of (number of idle TCHFs + number of PDCHs that can be preempted + number of idle TCHHs/2) is greater than four and is greater than the number of TRXs. In addition, idle TCHFs or PDCHs that can be preempted exist in the cell. 3. Number of SDCCHs in the cell + 8 < CELLMAXSD.

So it means that condition "(number of idle TCHFs + number of PDCHs that can be preempted + number of idle TCHHs/2) is greater than four and is greater than the number of TRXs" is needed to set some buffer for the TCH idle channels, to prevent full conversion into SDCCH and causing a TCH congestion before reverse conversion will be performed. In case if the TRX number in the cell is <=4 At least 4 idle TCHF or 8 TCHH should be available in the cell to allow TCH/PDCH conversion into SDCCH. Or this buffer will be increased respectively to the TRX number.
I hope this will help you.

[engaom]

Thanks Vladislav (http://www.finetopix.com/member.php?70566-Vladislav)

So finally these two conditions just to keep a buffer for the available TCHs in the cells,

[Vladislav]

Thanks Vladislav (http://www.finetopix.com/member.php?70566-Vladislav)

So finally these two conditions just to keep a buffer for the available TCHs in the cells,

Yes, you are right.
Please refer to the dyn SDCCH conversion conditions from my previous post.
If this the answer which you were looking for, I will be pleased if you add me the reputation.
Thanks.

[engaom]

Reputation added

[engaom]

One more question regarding the SDDCH reversion procedure

As per Hedex;The SDCCH reversion procedure lasts less than three seconds.
Also
If one or more of the selected SDCCH/8 channels are busy, the SDCCH reversion procedure is as follows:
1. To prevent call disruption on the selected SDCCH/8 channel, the BSC triggers the timer, waiting for the release of channels.
2. The BSC sets the channel status to "SDCCH/8 converted to TCHF, waiting for idle channel" to prevent these channels from being assigned before reversion.
3. If the sub-channels are still busy when the timer expires, they are released forcibly.
4. When all the selected SDCCH/8 channels are idle, the BSC follows the related procedure for reverting the idle SDCCH.

I have a conflict between the above procedure ,specially the Timer expiry and the 3 Seconds Timer, with the flow chart below in Huawei Presentation.
Where C=TCH Min. Recovery Time (not mentioned in Hedex feature descrption)

But the Chart is not clear at all to understand.

32863

[Vladislav]

One more question regarding the SDDCH reversion procedure

As per Hedex;The SDCCH reversion procedure lasts less than three seconds.
Also
If one or more of the selected SDCCH/8 channels are busy, the SDCCH reversion procedure is as follows:
1. To prevent call disruption on the selected SDCCH/8 channel, the BSC triggers the timer, waiting for the release of channels.
2. The BSC sets the channel status to "SDCCH/8 converted to TCHF, waiting for idle channel" to prevent these channels from being assigned before reversion.
3. If the sub-channels are still busy when the timer expires, they are released forcibly.
4. When all the selected SDCCH/8 channels are idle, the BSC follows the related procedure for reverting the idle SDCCH.

I have a conflict between the above procedure ,specially the Timer expiry and the 3 Seconds Timer, with the flow chart below in Huawei Presentation.
Where C=TCH Min. Recovery Time (not mentioned in Hedex feature descrption)

But the Chart is not clear at all to understand.

32863

Hi Engaom,
I also have the presentation from which you took the diagram.
My understanding is next:
- every 3 seconds BSC checks criteria "Idle SDCCH number > Idle SD Thrsh+8
- if "yes" it will deduct 3 from TCH Min. Recovery Time defined value (note that this is the same 3 seconds as the value of the 3seconds timer)
- if "no" it will add 12 to the TCH Min. Recovery Time defined value
- next step - if C (TCH Min. Recovery Time) expires (become 0) - then algorithm will switch back the channel if there will be such and restart 3 sec timer
- if C doesn't expire than 3 seconds timer will be just restarted.

This is an internal Huawei algorithm which cannot be modified. The purpose of it from my point of view is to increase automatically TCH Min. Recovery Time in case of low number of idle SDCCH to prevent SD congestion. Actually I never check if the algorithm really works like this on practice.
So you can try to make some test cases ))