Impact of the Angular Spread and Antenna
Spacing on the Capacity of Correlated
 MIMO Fading Channels

Mohammed Abdo Saeed , Borhanuddin Mohd Ali , Sabira Khatun , and Mahamod Ismail
 Faculty of Engineering, Universiti Putra Malaysia, Malaysia
 Faculty of Engineering, Universiti Kebangsaan Malaysia, Malaysia

Abstract: It has been shown that the capacity of a multiple-input multiple-output system increases linearly with the number of antennas, provided that the environment is rich scattering. However, this increase in the capacity is substantially degraded if the multiple input multiple output channels are correlated. In this paper, the capacity of correlated multiple input multiple output fading channel is investigated for laplacian and uniform angular energy distributions that implicitly represent two different scatterer distributions. The effect of the spatial correlation of a uniform circular antenna array is considered. Optimal power allocation is implemented to maximize the capacity. Through extensive Monte Carlo simulations, the results show that multiple input multiple output channel capacity is a function of the angle spread and antenna spacing. These two parameters play a major role in dictating the spatial correlation which in turn affects on the capacity. Large angle spread leads to lower correlation between the antenna elements and consequently higher capacity. The degradation in the capacity can be reduced by increasing the spacing between the antenna elements.    

Keywords: MIMO systems, capacity, correlation, scattering distributions.