---

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 user was shown to be N r if the units employ space-time trellis codes even if the units transmit asynchronously. Here, we consider the case when all units are synchronized and employ Quasi-Orthogonal Space-Time Block Codes (N 2). It is proved that in this case a receiver with xvi J + r 1 antennas, with r 1, can separate the transmitted signals of all units and provide each unit with a diversity order of N r.

---

Mohammad Usman, Education, 2008 Ph.D. in Electrical and Computer Engineering, University of California, Irvine, 2005 M.S. in Electrical and Computer Engineering, University of California, Irvine, 2003 B.S. in Electrical Engineering, Sharif University of Technology, Tehran, Iran

---