Use As Bluetooth Controller?


#1

Hi, I really don’t know much about radio tech but I’ve been interested in learning and am now faced with the need to buy a new Bluetooth controller. Rather than spending $50 on a Bluetooth 4.0 controller, I’m wondering whether now is a good time to invest in a S.D.R. controller like LimeSDR or LimeSDR Mini. Does anyone here have any experience using S.D.R. as a Bluetooth controller? What would be necessary to get working with bluetoothctl? Any insight would be appreciated.


#2

Generally speaking, replacing a commodity Bluetooth or WiFi etc. controller is not a good use case for an SDR, as they require a lot more processing power to run the software required and a cheap dongle is going to be far more cost effective and energy efficient. Where they come into their own is if you wanted to do something more advanced/unusual, such as analyse Bluetooth or WiFi, develop some extensions to existing standards, or perhaps R&D for a new version. There will be other examples, but you get the idea.


#3

Yes, thank you. I bought a Bluetooth controller for the time being but I do still like the idea of using a more versatile tool where possible in the future. Call it a bad habit or just curiosity. Could you give me an idea of how much system processing power this would require? I suppose it would depend largely on the SDR controller? Is there any way to offload the processing to a GPU, or maybe apply some software/firmware filtering for the Bluetooth controller logic on the SDR controller? Sorry if these ideas seem far fetched.


#4

It’s hard to say really.

It will depend on the Bluetooth version and bandwidth etc.

Yes, that’s likely possible, provided there is GPU code available for the compute intensive DSP involved, or you are prepared to write it.

I’m not really sure what you mean by “SDR controller”. An SDR is basically an extremely fast sound card and in the case of the LimeSDR, capable of handling millions of samples per second. It can be an enormous amount of data and hence compute intensive. But generally the SDR is “dumb” and doesn’t have a controller as such. The computer it connects to runs the software-defined part (digital signal processing and upper layers of a comms stack). You can implement some DSP in the FPGA on a LimeSDR and in fact the transceiver IC on the SDR has some “hard IP” DSP for digital filtering etc. But it’s not like a BT or WLAN etc. controller.

It’s not far fetched at all.