Hi Experts,
In LTE CCE failure, i have UL with much more failures than DL.
Vendor is Huawei.
In 5G Huawei, I see a parameter to control rate of UL CCE.
Do you know similar parameter for LTE?
In UL you can change CQI adjustment step from 100 to 10, initial cqi adjusment as 4, pucch format 2 as rb saving or random if UL CCE rate too is high.
Initial CQI delta as -4.
Not 4.
You will high CQI acceleration I guess and lot of users.
UL CCE issues can be due to PUCCH congestion I guess srs congestion too can play a role.
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Pucch congestion lead to DL CCE failure also.
Because DL scheduling need Pucch resource.
After DL SINR you get CQI and then MCS.
If there is rapid acceleration it will impact UL scheduling too.
High CQI adjustment step is always a worry in high user cases.
Sorry, UL scheduling is for UL data.
DL SINR is a factor of DL scheduling.
Ok not a problem.
I have changed CQI adjustment step if 100 to 10 and PUCCH format 2 allocation as random and found some gain in this KPI.
How are you correlating PUCCH congestion and CCE failure?
The CCE failures usually means that PDSCH resource is available for a user but the number of CCEs are exhausted. So the allocation failed.
UL cce exhausted.
So this two Huawei parameters work and if high retransmission rate make sure RACH is happening on contention free case.
There is ho ra switch and unsync ra switch.
I believe srs too can have UL issues.
It is just one cause of CCE allocation failure.
I mean that even cell have availabe CCE resource, but pucch resource is not enough.
So scheduling will fail because DCI infor carry not only pdsch resource, but also pucch resource for UE reporting.
I don’t think DCI carries the PUCCH resource.
Are you sure?
PUCCH configuration is provided to the UE in SIB2.
If there are no PUCCH resources, UE will not be scheduled. No DCI will be sent.
So if no PUCCH resource CCE allocation is failed?
In short you have to check.
Yes. But that is not CCE failure I guess.
CCE allocation failure is CCE not scheduled.
Yes, correct.
Uci and dci scheduling is part in uplink and downlink to play with.
This are connected in mac and physical layer only.
No other layer involved.
If rach going on contention based in ho assume how many failures can happen.
In sync out if contebtion based hapens.
Assume issues.
8 users enjoys same signature in contention free at a time.
In contention based unfortunately one.
Normally CCE failure is I have the PDSCH for that UE, but no PDCCH.
But in case of this scenario, PDSCH will not come into the picture since the UE has not reported the CQI due to congestion.
CCE is PUCCH in Uplink.
And PDCCH in Downlink.
Without CCE no data.
Be it PUSCH or PDSCH.
If your UL CCE is 40 to 50 percent all the time it is issue.
No…for UL scheduling eNB uses DCI format 0.
PUCCH resource configuration is given in SIB2.
In 5G DCI, there is pucch resource field. But 4G DCI, I don’t see.
That is comnon pucch. All UE can use it. But when report CQI, UE should know which pucch resource is reserved for it.