PDDCH CCE Improvement in Medium and Poor RF Scenarios

Hi Experts.

CCE is nothing but control channel element during PDCCH scheduling.
We have four format in PDCCH.Format 0 and 1 uses 1 and 2 cce respectively.
Format 2 and 3 uses 4 and 8 CCE respectively.
Which means user is in poor SINR or poor RSRP.
So we have pdcch coverage enhancement to improve but it has it drawbacks too.
But poor scheduler user will get bad throughput.
So proper physical optimisation will definitely improve it.
RF improvement is PDCCH agg CQI and BLER.

We have four agg. 1 and 2 CCE users in good RF.
4 CCE in medium and poor.
8 CCE very bad RF.
So sometimes medium rf user can consume 8cce, and we don’t want that to happen as it consumes more rb. More RB consume in PDCCH will have an impact on PDSCH Throughput.

We have two cases for example of using more CCE in pdcch:

  • Case for remote areas in poor RSRP.
  • Case for city in poor SINR.

Any suggestion?

1 Like

Hi, @parkarnadeem86.

There is no free meal! Keep in mind that, if you play with the eNB scheduler to be more loose with PDCCH Agg. Level (reducing average agg. level), and the scheduler is already working in an optimum way, artificially reducing the agg. level will save PRBs and reduce the PDCCH load, but you may increase BLER, increase retransmissions, reducing your effective throughput, which in the end, may even not result in PRBs savings. What I`m trying to say is, maybe you are seeing a user as medium quality, but in fact it is experiencing high bler, thus, agg8 is being used correctly.

High PDCCH aggregation level is more as reflection of a bad geometry of your cell (as the two cases you pointed), than a issue per se. Unless your scheduler is being extremely conservative, which by this time, in LTE, the schedulers are working more or less, well optimized. On 5GNR, since it is the beginning, things may be different.

But yeah, I`m assuming already an optimized scheduler. If not, each vendor have different parameters and features to make PDCCH more or less robust. For instance, Nokia has its own link adaptation applied to PDCCH and some extra features like LTE2026 to play with. Another example is the parameter LNCEL: pdcchAggDefUe which may also impact somehow the average PDCC agg level.

My suggestion to you is, grab the features list and parameters list and look for “pdcch” in there :slight_smile:

Dear 8CCE Means high bler i get it,but sometimes medium rf is there and bler is not that bad but still it comsumes rb.meaning cqi and bler are acceptable say cqi is arnd 7 to 8 bler is with range that consumes rb for no reasons,More user camped on 16 and 64 qam,we have cqi and bler kpi where i see its good but 8 and 4cce are used. example to go with as CQI in daily trend is more than 9,bler is around 10 to 12 percent both ul and dl,qam 64 users-60 percent,16 QAM-25 PERCENT,QPSK USER-15 PERCENT,mcs too is good,but 8 cce and 4 cce is more than 35 percent where 8 cce is arnd 20 percent.in this case there will be less issue of retransmission but unnecessary use of 8cce.if bler is very less that too is bad as low ibler too creates low mcs and throughput thats why ibler targetis 10 percent,we have features when ibler is low than target we increase ibler a bit for data throughput.