Expected throughput on nrf52840

RE: Expected throughput on nrf52840

Nivetha — Thu, 03 Aug 2017 13:49:47 GMT

Thanks Bjorn! I will:)

RE: Expected throughput on nrf52840

bjorn-spockeli — Thu, 03 Aug 2017 13:43:55 GMT

@nivetha: I suggest that you read this blog post, it goes through the various link settings.

RE: Expected throughput on nrf52840

Nivetha — Thu, 03 Aug 2017 13:34:17 GMT

I am using nrf52840 and set the connection interval as 10ms. I sending 10 samples/10ms. I see there are a lot of delays in the reception of samples. Do I have to set the connection interval to 7.5 ms?

RE: Expected throughput on nrf52840

bjorn-spockeli — Fri, 07 Apr 2017 14:27:51 GMT

Yes, but that was with 7.5ms connection interval, 23 ATT MTU with Data Length Extension and Connection Event Extension disabled.

RE: Expected throughput on nrf52840

Gary — Fri, 07 Apr 2017 14:20:47 GMT

According to this blog post devzone.nordicsemi.com/.../ it seems that Ole Bauck was getting 21.3 Kbps for BLE 5 Long Range.

RE: Expected throughput on nrf52840

bjorn-spockeli — Fri, 07 Apr 2017 14:05:33 GMT

Using the same method that the Bluetooth SIG to calculate the theoretical throughput, see this blog, I arrive the following calculations.

Time to send 265byte PDU @ 125kbps: 265*8bits/125kbps = 16.96ms

Time to receive 10byte PDU @ 125kbps: 10*8bits/125kbps = 640us

The Inter frame space, T_IFS ,the time interval between two consecutive packets = 150us

The usable payload that of a single ATT packet that fits inside the max PDU size is 247bytes, thus the theoretical throughput should be

247*8bits/(640us + 150us + 16960us + 150us) =~ 109kbps

If you have set the connection interval to 400ms and have Connection Event Extension enabled then you should be able to fit 400ms/16.96ms =~23 packets in one connection event, but it sounds like you're getting around half of that. I will look into this and update my answer.

RE: Expected throughput on nrf52840

Gary — Fri, 07 Apr 2017 08:14:55 GMT

Hi Bjorn, yes I have both Data Length Extensions or Connection Event extension enabled. What throughput should I be expecting? 125Kbps?

RE: Expected throughput on nrf52840

bjorn-spockeli — Thu, 06 Apr 2017 14:37:35 GMT

I am not able to reproduce the 56.98 Kbps with a 400ms interval and a MTU of 247. Do you have Data Length Extensions or Connection Event extension enabled?

RE: Expected throughput on nrf52840

Gary — Thu, 06 Apr 2017 07:51:47 GMT

Daniel, thanks for your comment. I was using a MTU size of 247 and a conn interval of 7.5ms. I wrongly assumed that 7.5ms was the best. However I tried 50ms and I am getting better throughout now. I see from the blog post that this is because of the "connection event length extension". Duly noted!

So now the 2MBPS and 1MBPS links are performing as I would expect: 1336.79 Kbps and 746.94 Kbps respectively. However the best I can get out of the CODED is 56.98 Kbps with a 400ms interval and a MTU of 247.

Any thoughts on how I could improve the CODED throughput?

Thanks, Gary.

RE: Expected throughput on nrf52840

Daniel Wang — Wed, 05 Apr 2017 19:46:44 GMT

What Connection interval and ATT MTU size are you using? Have you read the blog-post here ?