52840 long range mode real transmit speed and distance

[Carey]

Hi,  Our customer use 52840 transmit voice data, they use long range mode , the actual speed is 50-60Kbit/s in 10m distace. but when the distance is more than 50m, the speed would decline to 5-6kbit/s.  is it normal?  or some software or hardware configurate is not right?  I see the datasheet for long range mode the speed is 125kbit/s, but how much meter it can transmit for keep this speed?

by the way, customer said: the reason for the transmit speed decline just beacuase the softdevice would check the trasmit data package, if it have error, it would repeat transmit again, this ARQ (Automatic Repeat Request）would decline the transmit speed when distance is far, customer want disable this funtion becauce their voice data do not need the data is totally right, even some data trasmit error it do not influence the voice quality. is it possible for reach customer's demand?

[Einar Thorsrud]

Hi,

It is difficult to say exactly what is normal and what is not, as the range is effected by a number of factors. However, it is expected that as the range increased you will see more and more packet loss leading to a reduction in throughput. Note that 125 kbps is the speed on the link layer. You can never (not even theoretically) achieve a data throughput this high. A practical maximum speed of 60 kbps is reasonable.

Regarding retransmissions, Bluetooth 5.2 introduced a few new features indented for LE Audio, which can also be relevant for other use cases where you do not want retransmissions, broadcast isochronous streams (BIS) which are connectionless. We do not support that with long range / coded PHY though as LE Audio requiers 1 or 2 Mbps, but in principle connectionless communication should be possible also with coded PHY (if/when the stack supports it).

Br,

Einar