A basic need for a communications system is the need to cancel the channel noise and other interfering signals that can sometimes be considered as an internal and therefore are known.
As an example, one can observe the communication between a diver and a submarine, which her engine interferes with the communication.
The goal of this set of problems is to filter the interfering signal which is a near and strong signal while minimalizing the influence on the received desirable far signal.
A problem of this kind is called a near-far problem.
In our project, we dealt with this problem occurring in an underwater channel and using acoustic signals as the near and far signals.
We have implemented various algorithms for signal filtering (RLS, NLMS). We have also implemented an improvement of the NLMS algorithm that uses an estimation of the communication channel.
We examined the solution on simulated signals and real signals from a sea experiment.
Simulation results show a minimal 20dB attenuation of the near signal while not harming the far signal,
while results from the sea experiment show a minimal 15dB attenuation.
We have concluded that adding a successful preliminary channel estimation stage improves the filtering results.
Dr. Roee Diamant