Receiver Design and Signal-to-Interference-Plus-Noise Ratio Calculation in Multiuser Multiple Input Multiple Output Systems with Imperfect Channel State Information

Multiuser multiple input multiple output systems play a key role in providing advanced mobile broadband and vehicle communication services. The performance of the uplink of these systems depends critically on the receiver architecture and on the quality of the acquired channel state information. A popular approach is to design linear receivers that minimize the mean squared error of the received data symbols. Unfortunately, most of the literature does not take into account the presence of channel state information errors in the symbol error minimization. In this lecture I develop a linear minimum mean squared error receiver that employs the noisy instantaneous channel estimates of each user to minimize the mean squared error and highlight the dependence of the receiver performance on the pilot-to-data power ratio. By invoking the theory of random matrices, I calculate the users’ signal-to-interference-plus-noise ratio (SINR) as an implicit function of the number of antennas and the pilot-to-data power ratio of all users. Numerical results indicate that this new linear receiver outperforms the classical mismatched multiuser receiver. The implicit expression on the SINR can advantageously be used to design a sum-rate maximizing power control algorithm. Interestingly, under some mild assumptions, when mobile stations tune their respective pilot-to-data power ratios in a distributed fashion, the system converges to a Nash equilibrium. Numerical examples illustrate that the proposed receiver design and the associated pilot-to-data ratio tuning algorithm give superior performance in terms of mean squared error and sum-rate and thereby improve the quality of mobile broadband and vehicle communication services.