Most common low-cost Bluetooth modules used in micro-controller based projects are limited to around 1 Mbps thru Serial Port Profile (SPP). In addition, while the modules can transfer short data packets at all baud rates, they halt or fail completely when trying to achieve sustained high data rates. How to successfully transfer/stream data at all available baud rates for prolonged period of time? Are there any other feasible options for use i.e. different profile of Bluetooth in this case?
The standard data rate of 1 Mbps and ( cough! ) "enhanced" data rate of 2Mbps is pretty much what you have to work with. The high speed devices are still fairly expensive and uncommon, as you mention, those get you to 25Mbps. That is the native symbol rate. So not much to "fix" there.
As for Bluetooth cutting out? That's not a feature of Bluetooth, it could be a number of factors specific to your use case: drivers, RF environment, the transport methods, the computing devices. I consider that not to be an intrinsic Bluetooth issue. For synchronous transfer near maximum throughput, you do not have an throughput to retry lost block because the aggregate of valid and retried data exceeds the available throughput. So you cannot run at 1Mbps, as there is no room for errors. The strategy is to reduce the bulk of the data, leaving ample headroom.
For asynchronous data transmission, you need s TCP-like transport mechanism. Heck, even things like Z-Modem does a block integrity check and re-transmission, is appropriate.
Another factor is the RF space. Bluetooth devices come in 3 distance ranges - in some cases the only difference is the type of antenna in the device. The maximum range of 100 meters is achievable. Its also possible to attach yagi antennas to bluetooth interfaces dramatically extend the range. I have, myself, sent bluetooth over 500 meters with very cheap yagis. You can even do this with low power devices. More gain is always better,
The point of the above paragraph is that if you improve the gain of the antennas, you can have much more immunity to ambient RF. Improving the SNR will help increase the throughout.
Hope that helps.
@Robert Mahar: Thank you very much for your detailed answer. While working on our wearable device, like you mentioned, we have considered the RF space and tested performance in a isolated area i.e. at least where there is no other BT device within range. In addition, LOS and off-LOS communication rates were also tested. Interestingly, while testing with different Bluetooth-UART modules, it was found that the throughput increases, if not reaches its full theoretical baud rates, if a small delay was set between data packets. As this gives the module's internal electronics to resolve any jitter and/or corrupted data, this improves overall data rates than when without the delay. But again, that is also limited and is not high enough for multichannel high-resolution data.
For now, we are using the technique mentioned.
Dear Sarker;
Why dont you go for any alternative solution like esp 8266 wifi module offer high data rate?
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