How to Efficiently Decode Non-Standard Serial Signal
You could possibly use an FPGA instead of a Microcontroller to decode and buffer the wireless datastream. Then use the ARM processor to flush the FPGAs buffers (e.g. using a SPI interface) and ship the content out the USB Comm port. It's work, but an FPGA should be able to keep up easily so long as you are able to service it often enough to guarantee that its hardware buffers don't overrun (or if you can deal with dropped data at a higher level of the protocol).