In this thesis we study the effect of interference and methods of coping with it in a wireless network. We approach the problem from three different perspectives. The rst which involves physical layer is a method to cancel out interference in a multi-access channel. We consider J transmitter units each equipped with N transmit antennas over wireless Rayleigh fading channels. Previously, it was proved that when each transmitter unit has N transmit antennas, using (J 1)N + r receive antennas for any r 1, the receiver can completely separate the signals of J users. The provided diversity to each...