Hi,
Scenario:
Two nRF52832DK boards on a table, approx 20 cm from each other, +4dBm output power.
Payload length is ~60bytes.
Running at 1Mbps gives me less than 0.1% PER, running at 2Mbps gives about 25% PER. (everything else kept identical)
Is this expected, or is there something at play here?
Nope, no WiFi or anything else... Spectrum is almost empty here... the same difference regardless of what channel I'm using....
And at that distance, if anything would affect the reception to a large extent it would probably be receiver saturation in that case.... But it that case, why such a difference between 1Mbps and 2Mbps...
Nope, no WiFi or anything else... Spectrum is almost empty here... the same difference regardless of what channel I'm using....
And at that distance, if anything would affect the reception to a large extent it would probably be receiver saturation in that case.... But it that case, why such a difference between 1Mbps and 2Mbps...
BLE is FSK so IMD in the receiver shouldn't be an issue. What software are you using to measure PER?
Also is highly dependent on how you load the channel, hence the software question. The raw rate is 2Mbps but does not include all the BLE overhead. So actual rate is less. If you just try to shove 2Mbps through the pipe you will always see a high packet loss due to the overhead.
Here is some more info on the expected throughput: infocenter.nordicsemi.com/index.jsp
Expected throughput is irrelevant in this topic... This has simply nothing to do with throughput at all actually...
I donated know what's confusing with the question... And where did BLE overhead come in to the question?
Let me clarify the question again so that we please could leave throughput and BLE overhead out of it since it's irrelevant... I'm not even using the soft device... And throughput and packet error rate is two completely different things, even though PER can influence the throughput...
If using 1Mbps the counter is always in the range 999-1000, if using 2Mbps it's always in the range 700-800. This is regardless of what channel F I'm running on.
Sorry I referenced throughput. Most people test PER in respect to throughput. This is a requirement during ETSI testing and often is brought up in this forum.
What you are describing then is really lost packets and not PER since you are counting the number of received packets and not a ratio of CRC good vs. CRC bad packets. With your test setup it would be impossible to tell the difference between packet not sent, packet sent but not received (ie, lost) and packet received but bad and CRC error. You should improve the robustness of your test method by including counters on both ends and not just assuming the timing works out. Also on the receiver you should catalog CRC good vs. CRC bad events.
Another thought is in the mode you are testing you can do BLE2Mbps and Nordic Proprietary 2Mbps. The options show up in the enumerations for the mode register. There are minor differences in the gaussian indices for the GFSK and I believe that is it. It would be interesting if there was a difference.
Finally, even though you are convinced it is RF quiet in your local you should try outside of the ISM band just to be sure. The nRF52 operates from 2360 to 2500 MHz.
There are a lot of discussions on PER testing on this blog. Here are some good links: devzone.nordicsemi.com/.../ And a link to DTM PER testing: infocenter.nordicsemi.com/index.jsp
Please post back your final conclusion on the issue. It would be interesting to know what caused the problem.
