Bluetooth 5.0 File Transfer

[alan.kim]

Hello, community. 

I wonder Bluetooth 5.0 on nRF528xx can be used for file transfer. Bluetooth 5.0 has maximum 2Mbps, I expect that there is no problem to tranfer files such as audio, video files. However, I have not tested yet file transfer on Bluetooth 5.0. If you tested file transfer over Bluetooth 5.0, Please give your result or idea. 

[ovrebekk]

Hi Alan

I wrote a demo a while back to transfer pictures from an nRF52/nRF52840DK to a phone over Bluetooth 5, but in principle you are right that any kind of file can be transferred over Bluetooth. 

The main issue is that the transfer rate varies a lot from phone to phone. The best results we have seen is from the Samsung Galaxy line, where you can see speeds up to 1200kbps in the 2Mbps mode, while some phones can't do more than 100kbps or less. 

You can find my image transfer example here:

https://github.com/NordicPlayground/nrf52-ble-image-transfer-demo

And the Android app source:

https://github.com/NordicPlayground/Android-Image-Transfer-Demo

Best regards
Torbjørn

[awneil]

I'm not sure if it's that the phones actually can't do it - or if they just decide that they won't.

I have certainly seen cases where a particular phone (including Samsung phones)  will give "slow" parameters on one connection, and then "better" parameters on the next connection!

[ovrebekk]

As an app developer the result is the same ;)

I suspect that some phones limit the throughput artificially to provide a more consistent experience over time, and to reserve room for other protocols such as Bluetooth classic or WiFi. 

iOS as an example won't give you access to the radio more than 50% of the time for BLE traffic, which reduces the maximum throughput, but ensures less variation depending on what else the phone is doing at the time. 

Getting different parameters at different times can be frustrating for sure. My best suggestion would be to stay persistent on the nRF52 side, and attempt multiple times to get the connection parameters you want. For high throughput I have found a 15ms connection interval to be a near optimal setting, at least across Samsung and Apple phones. 

Best regards
Torbjørn

[awneil]

ovrebekk said:

As an app developer the result is the same

Indeed!

ovrebekk said:

I suspect that some phones limit the throughput artificially to provide a more consistent experience

Yes - that's my theory, too.

ovrebekk said:

Getting different parameters at different times can be frustrating

No kidding!

#PhonesLimitBLESpeed