Suppose I have a signal which varies between two frequencies (which represent a stream of binary data). I think this is called BFSK. I have the entire signal already sampled. Let's say each 'bit' lasts 10ms. My plan was to have bins of 10ms, and do FFT to find the dominant frequency, and deduce the bit from that.
My problem is finding the start position of the sequency. The signal is garbled with noise, and has a significant RMS white noise. I have attached a picture of what I'm trying to convey. Note that the actual signal's amplitude won't be as differentiable between the unwanted noise and the wanted frequencies.
How can I find where the 'wanted' signal starts? Should I be trying a binary search tree (halving each window or something), or is there a more direct approach?