Fault Tolerance of Quantized Unitary Precoders

Precoding based on channel state information (CSI) can help improve the performance of orthogonal space-time block codes (OSTBCs). Optimum precoders require a fairly detailed description of the channel singular vectors motivating the use of limited feedback communications to send some quantized form of the precoder to the transmitter. To this end, the singular value decomposition (SVD) is the fundamental step in extracting the singular vectors of the channel. In this paper we revisit a limited feedback technique based on the quantization of the dominant right singular vector of the channel matrix. Lifting the assumption of perfect channel estimation at the receiver, we investigate channels affected by Gaussian noise, line of sight component, and phase uncertainty. We also assume a more general channel model that incorporates channel correlations. Our simulations show that the quantized nature of the precoders provides the system with resiliency to such impairments