The Digital Signal Processing Lab @ UCSD


Thesis Title

Performance Analysis of Antenna Diversity Based Wireless Communication Systems

Thesis Abstract

Exploiting spatial diversity is widely considered to be a promising approach for improving the performance of wireless communication systems. In this dissertation, we provide insight into the nature of various antenna diversity systems through an extensive statistical performance analysis. Through the derivation of closed form performance expressions, we improve our intuition and understanding of the effects of antenna diversity.

We first consider the Optimum Combining (OC) technique in receiver diversity systems. We examine the distribution of the signal-to-interference plus noise ratio (SINR) in the presence of co-channel interferers. Making use of the projection of SINR onto orthogonal subspaces, we provide some suitable approximations to the SINR distribution. Upper and lower bounds on system performance are also presented.

We then consider the performance of Maximal Ratio Combining (MRC) under more realistic system assumptions such as imperfect channel estimation and channel correlation. Exact closed form expressions for the SINR distribution and outage probability are obtained, for systems with Gaussian estimation errors. Using these expressions, the effect of channel estimation quality on system performance is investigated. The SINR distribution of a dual antenna system experiencing channel correlation is also derived in the presence of co-channel interferers, and the effect of correlation on the system performance is quantified.

We then extend the analysis to a multi-cellular setting, where there is interference from users within the same cell as well as from other cells. We analyze the uplink outage capacity improvements in code-division multiple-access (CDMA) systems using a fast power control scheme that can track the multipath Rayleigh fading component. A closed form expression for the outage capacity is obtained. It is demonstrated that the outage capacity is improved more than linearly with increasing number of antenna elements.

Finally, Maximum Ratio Transmission (MRT) based multi-cellular multiple-input multiple-output (MIMO) systems are considered. Closed form uplink outage probability expressions are derived for systems with arbitrary number of transmit and receive antennas, for both deterministic and statistical user power models. It is shown that using antennas on the receiver side results in better performance since transmit diversity does not combat interference from same cell users.

Year of Graduation: 2004