LTE downlink 256QAM modulation

Hello Experts:
What should I consider if I decided to add in LTE downlink 256QAM modulation in Down link adaption of my system?
Currently what’s supported is maximum 64QAM modulation.

High BLER.
Higher Throughtput in good coverage zones.

You mean if I have high bler when I move to 256QAM?
Why would it be higher?
It should be still less than 10% I guess.

Im trying to imagine a scenario that I have 64QAM in my system and then moved to 256QAM.
What check points should I do/execute to verify that the moving to 256QAM will not decrease performance of my network?

Yes. This is basic principle of wireless communication. Higher MCS will have higher BLER. eNB scheduler will try to maintain 10% BLER, if it cannot it will lower MCS until BLER to Throughput is optimal.

So if scheduler will try to maintain 10%, this is work of scheduler.
Why I should care of?
I just adding 256QAM to MCS options…

Tbh very minimal impact given schedulers are now very efficient to quickly fix BLER vs performance curve.
However, as I said, you may see instances where eNB assign 256QAM but has to lower MCS due BLER which may impact user experience (user will have to wait longer to get all data while scheduler fixes their MCSs, etc).

I was over simplifying it :slight_smile:.
You may want to check your network profile and decide whether average quality qualifies enabling 256QAM.
You can play with some parameters like initial MCS assigned is always 64QAM and 256QAM is only enabled after certain SINR/RSRQ.

I understand!

I’m looking exactly on checkpoints that I need in order to enable the opition of 256QAM, currently maximum is 64QAM.
So I’m trying to imagine some scenario of moving from 64QAM to 256QAM.
I mean in this …what should I check in order to verify that when I move to 256QAM - new added opition- my network system is good and having optimal good throughput.
Is the ratio betweek ack and nack must be changed when I add 256QAM to MCS opition?
I guess also need to check the point of code rate because it’s will affect CCE allocation.

Check vendor notes (Huawei provides full list of KPIs and counter to be checked after feature is enabled)
I would check following KPIs
BH Tput
Avg User Tpu
Average active user time on network during BH or Normal Hours
Drive Test --> MCS, Tput vs SINR, RSRQ
If all these are more or less same, my conclusion would be that feature is ok to rollout as default.


Appreciate really good suggestions!

May we still missing and other suggestion to be check?
Any one could help me to what to check? To give me checkpoint to be verified in order to verify that adding 256QAM to my feature is good and have no worries … any checkpoints experts?
What scenarios could happen when I add 256QAM option and need to be checked?

256QAM activation is just like activating the feature. The usage of 256 QAM is very minimal. If you are checking the usage of each individual modulation schemes using the available counters. You will also see the 256QAM Utilization in your network. Your spectral efficiency and cell/user throughput may improve if you get good number os samples.

256QAM usage in the DT will totally depend on your DL SINR, if it is good ~ 20 you will have 256QAM samples.
Plus, in Ericsson we have power head room parameter which is tailored for optimized use of 256QAM Modulation. In Huawei you may have more. Last but not the least, today it is very common to have 256QAM DL and 64QAM UL active by default.

Even 256 QAM in uplink is available.

Do you mean using 256QAM will improve the spectral efficiency and cell/user throughput?

Very minimum improvement seen in average user throughtput I remember hardly some kbps only between pre and post.

1024QAM DL is also available now, no?

The default is 64QAM no?
So implicitly need the default to be initialized with 256QAM.

I was discussing about different feature in LTE.

For your trial, you need to enable 256QAM feature. In Huawei, if I remember correctly, there used to be initialMCS parameter. Dont change that, leave that to 64QAM. Set correct parameters for 256QAM and let scheduler assign MCS whenever quality is appropriate.

Here is my struggle… which parameters should I consider/take into account when I enable 256QAM?

Actually Im asking what attempts/checkpoints should I do in order to examine/test when I enable 256QAM in downlink adaption?

That should be in vendor documentation.
All details we have mentioned above usually come with Feature activation pack.

We’ve discussed this already. Not sure what more info are you looking for. :thinking:

But I suggest review documentation and prepare an initial design with your team and/or vendor. If you have specific question about parameter or other interactions we can discuss more. Otherwise it’ll be difficult to answer open ended question.

256QAM in UL is now available, but haven’t seen 1024QAM DL anywhere in commercial network.

In Huawei RAN 3.1, UL 256QAM is trial feature, but later in RAN 5.1 it’s offical feature.