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

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

Multi-Hop Capacity of MIMO-Multiplexing Relaying Systems

Abstract-This paper derives the multi-hop capacity of OFDMbased MIMO-multiplexing relaying systems. MIMO-multiplexing relaying presents a spectrally efficient means of realizing mesh supports in wireless networks operating over licensed bands by providing separate links for access and mesh relaying services on the same broadband radio channel. We show that for an N xN MIMO-multiplexing relaying system with amplification factor α at relay nodes, R-hops relaying degrade the capacity by at most −N log 2 α 2R / 1 + R r=1 α 2r N r + RNlog 2 (N ) bits/sec/Hz. Therefore, greater capacity loss is experienced in MIMO-multiplexing relaying involving high order MIMO systems. We also illustrate that the capacity loss is independent of the OFDM configurations employed; thus network operators could employ higher OFDM configurations to compensate for data rate loss in access services when some of the MIMO-multiplexing links are dedicated to mesh relay. This pioneering analysis provides useful guidelines for network operators planning to employ MIMO-multiplexing option for mesh relay supports. Index Terms-Multi-hop capacity, WiMAX mesh networks, MIMO-multiplexing relaying, amplify-and-forward relaying, broadband wireless access