throughout sample TX power

[Ziyao Zhou]

Hi

I am using 4 nrf52833 DK to see the relationship with RSSI and Dara rate. I have two running the nordic uart service and print out the RSSI, they are using TX=0. And another pair is running throughput sample to test datarate. I need to make sure the TX power for both pair is identical so that the RSSI of central uart could be the RSSI for throughput sample.

Could you please advice me whether throughput TX is 0. And whether my way to test is OK?

[Susheel Nuguru]

You did not mention which SDK you are using, assuming that you are using our nRF Connect SDK.

You need to add CONFIG_BT_CTLR_TX_PWR_DYNAMIC_CONTROL=y in your prj.conf 

You would also need CONFIG_BT_CTLR_TX_PWR_DYNAMIC_CONTROL=y.

Just look at the SDK\zephyr\samples\bluetooth\hci_pwr_ctrl\src\main.c to see how it works.

Could you please advice me whether throughput TX is 0. And whether my way to test is OK?

Testing both test devices with TX power 0 is a good way to compare when there is another peer listening to the packets and then comparing RSSI. I cannot comment on the technical details of the experiment as I know very little technical details from your description.

[Ziyao Zhou]

Hi,

Thank you for your reply! Yes, I am using the NCS and did not add CONFIG_BT_CTLR_TX_PWR_DYNAMIC_CONTROL=y and CONFIG_BT_CTLR_TX_PWR_DYNAMIC_CONTROL=y. As I barely remember if there is no config the TX power will be default 0 dbm for both throughput sample and NUS sample. So I just want to confirm that two samples are both runnning with 0 dbm.

By the way, I have check the result and found that Datarate is not sensitive to the RSSI, is it correct? Are that highly relative or not. Thank you so much for your help!

[Susheel Nuguru]

Ziyao Zhou said:

As I barely remember if there is no config the TX power will be default 0 dbm for both throughput sample and NUS sample.

The default TX power will always be 0dBm in default NUS sample if you have not made any changes to it.

Ziyao Zhou said:

By the way, I have check the result and found that Datarate is not sensitive to the RSSI, is it correct? Are that highly relative or not. Thank you so much for your help!

If the data rate doesn’t change much when RSSI shifts between -50 dBm and -70 dBm, that’s totally expected for BLE on the nRF52. In this range, the connection is still strong, so throughput stays pretty stable. You’ll only notice a big drop when RSSI gets close to the receiver’s sensitivity limit, causing a spike in packet errors. So yes, within a certain RSSI range, the data rate isn’t heavily affected by RSSI.

[Ziyao Zhou]

Hi,

Thank you for your information. How about throughput sample, if no thing change it is running on TXP = 0dbm?

[Susheel Nuguru]

Yes, it should be on 0dBm by default.

[Ziyao Zhou]

Thank you for your information!

[Ziyao Zhou]

Hi, today I have do the test again and found different result. I am doing with 2M phy 251 bytes 320ms interval. All the environment is the same (open space). the first one is previous, the second is today's. Why they have such large difference. I have done many sets of experiments and all shows this difference

Or do you have some materials for the relationship between RSSI and datarate.Thank you so much!