Linear Precoder Design for Correlated Partially Coherent Channels with Discrete Inputs

Abstract:
We consider the single-user multiple-input multipleoutput (MIMO) precoder design problem for the spatially correlated partially coherent Rayleigh fading channels with discrete inputs. The objective is to design a linear precoder to adapt to the degradation caused by the imperfect channel estimation at the receiver and the transmit-receive antenna correlation. The system is partially coherent so that the MIMO channel coefficients are estimated at the receiver and its error covariance matrix is fed back to the transmitter.We derive the cutoff rate (CR) expression, an alternative to the mutual information (MI), and propose to use it as a design criterion to design the linear precoders. A linear precoder is obtained by numerically maximizing the CR w.r.t. the precoder matrix with a given average power constraint. Two step optimization algorithm is proposed to find a close-to-optimal precoder matrix. Precoders are designed to be used in conjunction with space-time block codes (STBCs). Numerical examples show that the performance gains of the newly designed CR precoders are significant compared to the CR optimized partially coherent constellations (PCCs) and conventional codewords.