BLE throughput from smartphone to ESP32

[jhulbert]

I am beginning to plan a project using an ESP32-WROVER-E and would like to measure the BLE throughput. I am looking to do OTA over BLE.

I have set up two ESP32's with the throughput client and server examples provided by Espressif. Both write and notify throughput report a data rate of ~91 kB/s which should be plenty for my application since the firmware file won't be more than a couple hundred kB.

To follow up on this, I am attempting to test the BLE throughput from a smartphone, acting as a client, to the ESP32, acting as a server (running example_ble_server_throughput.c). The problem I have is the phone app for this project doesn't exist and probably won't for a while. I have played around with some BLE client emulators such as nRF Connect for Mobile and LightBlue, but they only allow you to write characteristics by entering a value and pressing the write button. But to get the maximum throughput the server example needs the characteristic to be continuously written by the client (which is what example_ble_client_throughput.c does). I can only do one write at a time by physically pressing a button using these smartphone apps, so the data rate reported by example_ble_server_throughput.c is much smaller than what is possible.

Possible ways forward I have come up with are:

1. Use a different smartphone app to emulate the client.
- I have looked around a bit but haven't found something which does a continuous/looped write. I'm also not experienced in smartphone app writing and this is more of a viability test so its unlikely our app will be available anytime soon.

2. Just accept that the maximum throughput between a smartphone and ESP32 will be similar to the 91 kB/s reported between two ESP32s in the Espressif example code.
- I am not actually sure what may cause the phone-to-ESP32 throughput to be less than 91 kB/s. One possibility is the maximum MTU size is only 185 on iOS. I am interested in the throughput for iOS and Android though. If someone could provide insight or confirm this it would be the easiest way forward.

3. Modify example_ble_server_throughput.c to get a better reporting of throughput with nRF Connect for Mobile or LightBlue.
- Getting an accurate measure of throughput seems to require that data is continuously transmitted which doesn't appear possible with these two client emulators.

Any suggestions and insights are appreciated!