CMI analysis and precoding designs for correlated multi-hop MIMO channels

Abstract

Conditional mutual information (CMI) analysis and precoding design for generally correlated wireless multi-hop multi-input multi-output (MIMO) channels are presented in this paper. Although some particular scenarios have been examined in existing publications, this paper investigates a generally correlated transmission system having spatially correlated channel, mutually correlated source symbols, and additive colored Gaussian noise (ACGN). First, without precoding techniques, we derive the optimized source symbol covariances upon mutual information maximization. Secondly, we apply a precoding technique and then design the precoder in two cases: maximizing the mutual information and minimizing the detection error. Since the optimal design for the end-to-end system cannot be analytically obtained in closed form due to the non-monotonic nature, we relax the optimization problem and attain sub-optimal designs in closed form. Simulation results show that without precoding, the average mutual information obtained by the asymptotic design is very close to the one obtained by the optimal design, while saving a huge computational complexity. When having the proposed precoding matrices, the end-to-end mutual information significantly increases while it does not require resources of the system such as transmission power or bandwidth.

Joint source and relay precoding for generally correlated MIMO with full and partial CSIT

“…5. The proposed joint precoding schemes in this paper provide higher capacity than the existing schemes in [4] and [28,29,31] by numerical simulations.…”

“…Instead of colored noise, the relay precoder that maximizes the average capacity of a two-hop relay system where the destination lies close to some interferers was designed based on covariance information of the interferers-destination channels and the relay-destination channel in [26]. The papers [28][29][30][31] considered general MIMO relay systems having spatially correlated channels, colored noises, and mutually correlated source signals. Note that mutually correlated source signals arise from encoding operations on the bit stream including channel coding, modulation, and space-time coding at a transmitter [7,32].…”

“…In [28,29], the optimal structure of relay precoder that maximizes the MI of the generally correlated two-hop MIMO relay systems was obtained by using full CSI of two links and covariance matrices of the correlated source signals and the colored noises known at the relay. The papers [30,31] devoted for the case of the generally correlated multi-hop MIMO relay systems. With the full CSI of hops and the signal and noise covariance matrices at the transmitters (the full CSIT), the source and relay precoders were designed asymptotically by either maximizing the individual MI of each hop or minimizing the individual soft mean-squared error (MSE) of estimated signals of each hop.…”

“…In this paper, we investigate generally correlated twohop MIMO relay systems with mutually correlated source symbols, spatially correlated channels and colored noises. For the system capacity maximization, we propose joint designs of source and relay precoders in two cases of the full CSIT (like [28][29][30][31]) and the partial CSIT. The partial CSIT denotes full CSI of the source-relay link and covariance information of the relay-destination link and the source signal and noise covariance matrices known to the transmitters.…”

“…2. This paper develops the simplified precoding strategy based on the full CSIT in [31] to the iterative and simplified strategies based on the full CSIT as well as the partial CSIT. 3.…”