[Discuss-gnuradio] Detecting unipolar and repeating preamble on wired communications?

[Jeon]

I am trying to implement a preamble detection.

A couple of things that,
I'm not using wireless communication but wired communication.
And also, I'm not using a bipolar signal, but a unipolar signal.

(Bipolar: a signal swings between +A volts (or amperes) and -A volts; Ethernet, USB, Wi-Fi, ... are using bipolar signals,

Unipolar: a signal swings between +A volts and 0 volts)

Using a unipolar signal, I am having a difficulties on determining whether a signal has a repetition.

A preamble has a typical form of 1, 0, 1, 0, 1, 0, 1, 0, (and data payload follows)

and it is mapped into a real signal and received at a receiver: +A+n, n, +A+n, n, +A+n, n, +A+n, n, (and data payload follows)

(n is very small noise and fluctuation, n can be either negative or positive)

I think an optical fiber communication might use unipolar signalling, but I'm not sure.

Is there anyone already implemented unipolar preamble detection succesffully, or could anyone give me some hints on mathematical approach or something?

Regards,

Jeon.