Max packet number per CI for nRF5340

[PengLiu]

Hi, Experts,

We are evaluating BLE throughput (sdk-nrf-2.7.0 throughput sample) using nRF5340DKs. The CI is set to 6 i.e. 7.5ms. The PDU size is set to 251, PHY is 2Mbps.

The measured throughput is around 1040kbps, far less than the theoretical value 1300kbps.

The times include transmitting + IFS + receiving + IFS is 1400us, so the theoretical packet number within 7.5ms is calculated as 7500/1400=5. We suspects packet number of 4 is used instead of 5, thus the actual rate is 80% of theoretical value. Can anyone help confirm whether packet number of 4 is used for this case and for what reason the number is reduced by 1.

Thanks,

Peng,

[PengLiu]

Hi, Hung,

Understood now. 

Now one more question, is this kind of scheduling implemented by nRF5340 chip or by firmware?

Thanks,

[Hung Bui]

Hi Peng, 
It's the MPSL module that's handling the scheduler. It's a firmware library. 

[PengLiu]

Hi, Hung,

The start ratio (RF startup) time and post-processing time are all controlled by firmware? 

I saw they have the same values no matter how PDU size and payload per event are set using Online Power Profiler. 

Thanks,

[Hung Bui]

Hi Peng, 
No they won't change on the payload. Please consider increasing the connection interval to find the sweet spot that you can maximize the time domain when keeping the interval low. 

[PengLiu]

Hi, Hung,

So start ratio (RF startup) time and post-processing time are are all nRF5340 chip spec? Are they listed in datasheet or some other document?

Thanks,