Abstract

It is well known that the use of multiple antennas at both ends of a wireless communication link can provide significant capacity gains. However, this gain is significantly limited by co-channel interference (CCI) in realistic multi-cellular systems with aggressive frequency reuse. On the other hand, frequency resources are very expensive, and they must be managed as efficiently as possible. Thus, CCI mitigation is a key issue in improving system performance. In addition to CCI, imperfect Channel State Information at the transmitter, caused by channel mismatch due to many possible factors, yields further degradation in system performance.

In this thesis, we describe and evaluate downlink transmit beamforming, including using interference nulling and opportunistic transmission techniques to mitigate CCI from co-channel base stations. We also investigate the sensitivity of these techniques to time variations in the channel. Finally, we present the simulation results for both multicell-based and femtocell-based environments.