Performance Analysis of Two-Way AF MIMO Relaying of OSTBCs With Imperfect Channel Gains

In this paper, we consider the relaying of orthogonal space–time block codes (OSTBCs) in a two-way amplify-and-forward (AF) multiple-input–multiple-output (MIMO) relay system with estimated channel state information (CSI). A simple four-phase protocol is used for training and OSTBC data transmission. Decoding of OSTBC data at a user terminal is performed by replacing the exact CSI by the estimated CSI in a maximum-likelihood (ML) decoder. Tight approximations for the moment-generating function (MGF) of the received signal-to-noise ratio (SNR) at a user is derived under Rayleigh fading by ignoring the higher order noise terms. Analytical average error performance of the considered cooperative scheme is derived by using the MGF expression. Moreover, the analytical diversity order of the considered scheme is also obtained for certain system configurations. It is shown by simulations and analysis that the channel estimation does not affect the diversity order of the OSTBC-based two-way AF MIMO relay system.