Maximizing NRF52 & iOS BLE throughput in both directions

RE: Maximizing NRF52 & iOS BLE throughput in both directions

aaronxu — Mon, 03 Jun 2019 12:56:41 GMT

Great experiment! Any update since iOS13 will be released soon.

RE: Maximizing NRF52 & iOS BLE throughput in both directions

Vidar Berg — Mon, 03 Dec 2018 13:25:57 GMT

Based on your result (380 kbps) and the settings you use I'm pretty sure the throughput is again limited by the iPhone. We have measured 1447.2 kbps between two nordic devices.

RE: Maximizing NRF52 & iOS BLE throughput in both directions

Juju — Fri, 23 Nov 2018 10:39:25 GMT

Yes I have my own app and needed to experiment with different values for:

tx_mps / tx_queue_size for l2cap config
ble_data.len for sd_ble_l2cap_ch_tx()

I used:

tx_mps=512
tx_queue_size=6
ble_data.len = 255 (in my case data comes directly from SPI easyDMA)

Not sure how I can optimize further since I don't know about low level L2CAP transmission.

RE: Maximizing NRF52 & iOS BLE throughput in both directions

Vidar Berg — Fri, 23 Nov 2018 09:47:08 GMT

Thanks for sharing the results. Are you using a custom app to establish the L2CAP channel?

RE: Maximizing NRF52 & iOS BLE throughput in both directions

Juju — Fri, 23 Nov 2018 09:22:38 GMT

I was able to achieve around 380 kbps using a L2CAP channel with the stream going from the NRF52 to the iPhone which is much better than the original 128 kbps.

However, this is still below below the 400 kbps obtained in the other directions and without the lightweight protocol advantage of L2CAP.

I still need to try the L2CAP channel from the iPhone to the NRF52.

RE: Maximizing NRF52 & iOS BLE throughput in both directions

Vidar Berg — Wed, 21 Nov 2018 08:59:49 GMT

It actually supports 2 mbit even though it's LE v4.2. I confirmed the bitrate with a BLE sniffer.

RE: Maximizing NRF52 & iOS BLE throughput in both directions

Juju — Wed, 21 Nov 2018 08:50:02 GMT

Just to confirm, the iPhone 7 is Bluetooth LE 4.2 so the figures you are getting are with PHY=1 right?

RE: Maximizing NRF52 & iOS BLE throughput in both directions

Juju — Wed, 21 Nov 2018 08:11:11 GMT

Thanks, I will put some figures when I have them.

RE: Maximizing NRF52 & iOS BLE throughput in both directions

Vidar Berg — Wed, 21 Nov 2018 08:00:05 GMT

We have not tested a L2CAP channel with iOS as far as I know, but we have the OTS example if you want to try it.

RE: Maximizing NRF52 & iOS BLE throughput in both directions

Juju — Tue, 20 Nov 2018 17:11:40 GMT

Thanks for your reply so it seems to match what I am currently getting.

Did you ever check the possible throughput improvement using a L2CAP channel between iOS and NRF52?

RE: Maximizing NRF52 & iOS BLE throughput in both directions

Vidar Berg — Tue, 20 Nov 2018 14:36:15 GMT

Hello,

I expected the throughput to be roughly the same in both directions. To verify this I modified the ble_app_uart example in sdk 15.2.0 to transmit dummy packets and request 2mb phy. With this I was able to achieve ~400kbps+ with an iphone 7 running ios 12.1 (15ms CI, PHY=2, 185 byte MTU). However, the results seems to have been impacted by the fact that I had been running the ANCS example on the same DK prior to this test. After rebooting the phone (clears device cache) I was not able to get more than 128 kbps. In other words, it looks like the iphone is capping throughput at 128 kbps in some cases. I haven't found any relevant Apple documentation on this so not sure if it there's a proper way to override this.

Here are some throughput numbers with Nordic on both sides in case you haven't seen it:

Bluetooth Low Energy data throughput