Changing the CQI Feedback Cycle in Huawei

[youssef89]

Dear Experts,

The default value for CQIFBCK parameter (CQI Feedback cycle) in Huawei is 2 msec, what do you think of increasing this timer to 8 msec for example.

[giegala]

Hi,

longer CQI feedback cycle might increase HSDPA BLER and retransmission rate. Even with default settings HW is not doing well on HSDPA BLER. Nevertheless, the best is to try in field.

[rfsupp]

The results willbe be noticed at sites with more 15 - 20 HSDPA users:
- The RTWP will decrease about 3dB.
- The retransmission will increase a little bit (as expected).
- No throughput degradation

[youssef89]

Hi all,

Thanks for your Replies, but why do you think the retransmission will increase, although the CQI sent by the user is not so effective since it is adjusted by the NodeB according the BLER value ?

[kernel1]

thanks bro for this subject

[giegala]

Hi,

to my understanding BLER adjustment works by using lower CQI than UE reports for TBS selection. The quicker UE reports CQI, the more accurate description of the channel NodeB gets. So, delayed reports would lead to higher error in TBS choice:

- If TBS is too small for RF channel -> waste of capacity -> lower throughput
- If TBS is chosen to be too big for RF channel, UE will receive TBS with error -> lower throughput and higher BLER -> NodeB will chose smaller TBS than before -> TBS gets selected to be smaller for RF channel condition (error type 1) -> waste of capacity -> lower throughput

So, BLER adjustment will not compensate for TBS selection error