Optimized Power Allocation for Multiantenna Systems Impaired by Multiple Access Interference and Imperfect Channel Estimation

Abstract

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper presents an optimized spatial signal shaping for multiple-input–multiple-output (MIMO) “<emphasis emphasistype="boldital">ad hoc</emphasis>”-like networks. It is adopted for maximizing the information throughput of pilot-based multiantenna systems that are affected by spatially colored <emphasis emphasistype="boldital">multiple access interference</emphasis> (MAI) and channel estimation <emphasis emphasistype="boldital">errors</emphasis>. After deriving the architecture of the minimum mean square error (MMSE) MIMO channel estimator, closed-form expressions for the maximum information throughput that is sustained by the MAI-affected MIMO links are provided. Then, we present a novel power allocation algorithm for achieving the resulting link capacity. Several numerical results are provided to compare the performance achieved by the proposed power-allocation algorithm with that of the corresponding MIMO system that works in <emphasis emphasistype="boldital">MAI-free</emphasis> environments and is equipped with <emphasis emphasistype="boldital">error free</emphasis> (e.g., <emphasis emphasistype="boldital">perfect</emphasis>) channel estimates. By so doing, we are able to give an insight on the ultimate performance loss that is induced in MIMO systems by spatially colored MAI and imperfect channel estimates. Finally, we point out some implications about space-division multiple access strategies arising from the proposed power allocation algorithm. </para>