How to increase the Channel Sounding measurement rate on nRF54L15

[TG3112]

Hi,

I’m currently working with the nRF54L15 DK using the Channel Sounding Initiator with Ranging Requestor sample from the latest nRF Connect SDK. The setup runs successfully, I get continuous distance estimates (ifft, phase_slope, and rtt) on the initiator side.

However, I noticed that the measurement results always come in small clusters (about 4-5 repeated values) before they update again.
From what I understand, this corresponds to one Channel Sounding procedure containing several subevents.

My main goal now is to increase the effective measurement rate, becuase if I decrease the k_sleep() Value at the end of the code, I only increase the logging interval but not the measurement rate.

So which parameters in e.g. bt_le_cs_set_procedure_parameters() or bt_le_cs_create_config() actually determine the ranging / measurement frequency ? And what would be the maximum rate in Hz without any complications?

Thank you very much in advance!

[Amanda Hsieh]

Hi, 

The sample produces one new distance estimate per CS procedure (not subevent). However, note that the default configuration and parameters used in the sample ensure that there is one subevent per procedure. The reason you are seeing clusters may be due to the median filter, which is applied to a moving window of the 9 (DE_SLIDING_WINDOW_SIZE) last distance estimates. 

 

To increase the rate at which you receive new estimates, you need to reduce the procedure interval. This can be done by:

•  Decreasing https://github.com/nrfconnect/sdk-nrf/blob/main/samples/bluetooth/channel_sounding_ras_initiator/sr…
•  Decreasing the ACL interval https://github.com/nrfconnect/sdk-nrf/blob/main/samples/bluetooth/channel_sounding_ras_initiator/sr…. 

Note that if you decrease the procedure interval by "too much," there will probably not be enough time for the RAS (ranging service) to relay the CS measurement data from the rrsp to the rreq before the next procedure starts. This will lead to dropping of some procedures and perhaps an effectively reduced rate of new distance estimates.

One option to combat this issue is to reduce the amount of CS measurement data per CS procedure; note that this will always be at the cost of reduced accuracy. This could be done in a few different ways:

• Reducing the number of enabled channels in the channel map by setting fewer bits here https://github.com/nrfconnect/sdk-nrf/blob/main/samples/bluetooth/channel_sounding_ras_initiator/sr…
• Reducing the subevent_len https://github.com/nrfconnect/sdk-nrf/blob/main/samples/bluetooth/channel_sounding_ras_initiator/sr… and configuring the max_procedure_len https://github.com/nrfconnect/sdk-nrf/blob/main/samples/bluetooth/channel_sounding_ras_initiator/sr… to be equal to the subevent len
• Configuring submode as unused here https://github.com/nrfconnect/sdk-nrf/blob/main/samples/bluetooth/channel_sounding_ras_initiator/sr… (this may reduce the security of CS)

Regards,
Amanda H.