Achievable Rates of Full-Duplex MIMO Radios in Fast Fading Channels With Imperfect Channel Estimation

Abstract

We study the theoretical performance of two fullduplex multiple-input multiple-output (MIMO) radio systems: a full-duplex bi-directional communication system and a fullduplex relay system. We focus on the effect of a (digitally manageable) residual self-interference due to imperfect channel estimation (with independent and identically distributed (i.i.d.) Gaussian channel estimation error) and transmitter noise. We assume that the instantaneous channel state information (CSI) is not available the transmitters. To maximize the system ergodic mutual information, which is a non-convex function of power allocation vectors at the nodes, a gradient projection algorithm is developed to optimize the power allocation vectors. This algorithm exploits both spatial and temporal freedoms of the source covariance matrices of the MIMO links between transmitters and receivers to achieve higher sum ergodic mutual information. It is observed through simulations that the full-duplex mode is optimal when the nominal self-interference is low, and the half-duplex mode is optimal when the nominal self-interference is high. In addition to an exact closed-form ergodic mutual information expression, we introduce a much simpler asymptotic closed-form ergodic mutual information expression, which in turn simplifies the computation of the power allocation vectors. Index Terms-Full-duplex MIMO radio, bi-directional communication, full-duplex relays, fast fading channels. I. INTRODUCTION T His paper concerns radio frequency (RF) wireless communication systems or simply called radios. A radio can be used as a wireless relay between two other radios, which we call a relay system. Two radios can be used to communicate directly with each other, which we call a bi-directional system. Wireless relays have attracted a great deal of attention for next generations of wireless communication systems as relays can reduce the overall path loss and transmission power consumption and they also can increase cell coverage and capacity. A conventional wireless relay is half-duplex, which

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