BLE UART Bridge Throughput Limitation at 1Mbps PHY and 7.5ms CI — Packet Count per Interval?

RE: BLE UART Bridge Throughput Limitation at 1Mbps PHY and 7.5ms CI — Packet Count per Interval?

Pedro — Thu, 10 Apr 2025 14:34:21 GMT

Thanks Kenneth!

RE: BLE UART Bridge Throughput Limitation at 1Mbps PHY and 7.5ms CI — Packet Count per Interval?

Kenneth — Thu, 10 Apr 2025 13:25:34 GMT

Check out the https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/samples/bluetooth/throughput/README.html example in specific. That one should be optimized for throughput, even if the peer may not support all the features.

Kenneth

RE: BLE UART Bridge Throughput Limitation at 1Mbps PHY and 7.5ms CI — Packet Count per Interval?

Pedro — Thu, 10 Apr 2025 11:29:44 GMT

Hi Kenneth,

Thank you very much for the quick and detailed response. That definitely helps clarify things.

I’ve also come across another post on DevZone (link) which mentions the possibility of adjusting the following parameters to optimize throughput:

CONFIG_BT_BUF_ACL_TX_COUNT
CONFIG_BT_L2CAP_TX_BUF_COUNT
CONFIG_BT_CTLR_SDC_MAX_CONN_EVENT_LEN_DEFAULT

Any other config parameters I can tune for optimizing throughput?

Thanks again for your help!

Best regards,
Pedro

RE: BLE UART Bridge Throughput Limitation at 1Mbps PHY and 7.5ms CI — Packet Count per Interval?

Kenneth — Thu, 10 Apr 2025 11:10:17 GMT

Hello,

If you want to understand better timing and what is the limitation etc. I recommend to for instance attach a BLE sniffer or you can consider an Nordic PPK II to measure the current in real-time, this will then show the time-on air and find what is limiting the throughput.

There will be some pre- and post-processing required for each interval, adjustment for clock drift, and this may have quite a large impact when the connection interval is only 7.5ms. It may also be that the dongle you have for some reason close the connection event before you reach the entire period.

You can also indirectly use the online power profile app: https://devzone.nordicsemi.com/power/w/opp/2/online-power-profiler-for-bluetooth-le

I can see it show a maximum 230kbps.

From blogpost: https://novelbits.io/bluetooth-5-speed-maximum-throughput/ I can see he measure

Case 1 (PHY: 1 Mbps, ATT MTU = 23 bytes, DLE: enabled, Connection interval: 7.5 millisecs)

Data throughput reported by firmware:

Time: 36.11 seconds elapsed.
Throughput: 232.29 Kbits/s.
Sent 1048580 bytes of ATT payload.

Edit: I didn't really answer your questions directly, but I think the above blog post from novelbits explain what you should expect here and how it works.

Kenneth