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This paper is concerned with the joint optimization of user power allocation and distributed relay beamforming in two-way wireless relay networks in which multiple multi-antenna relays assist multiple single-antenna users. The design aims at maximizing the minimum information rate among user pairs subject to various practical power constraints at the users and relays. Since the nonconvex structure of the problem is highly complicated, the existing approaches to relax the design problem into a convex program do not appear to be applicable. To solve this challenging nonconvex optimization problem, we introduce auxiliary variables and cast the design problem into a d.c.(difference of convex functions) program. Then, we develop an efficient iterative algorithm of sequential convex optimization to obtain the optimized solutions. Extensive simulation results demonstrate that our proposed joint design outperforms the only relay beamforming design. [ABSTRACT FROM PUBLISHER]

In this paper, we are concerned with optimized linear precoding strategies for multiple-input multiple-output interference channels (MIMO-IFC). Under practical transmission power constraints, we aim at maximizing the sum-information-rate. To date, most developments could not directly address this problem. Instead, intermediate problems of simplification have been considered by means of alternating optimization, which fails to jointly optimize all the concerned variables. In this paper, we directly solve this problem by exploring its hidden d.c. (difference of convex functions) structure. The recast problem can be iteratively solved by d.c. iterations (DCIs), which guarantees the convergence to at least a local optimum. Numerical simulation results show that the proposed solutions offer improved performance. [ABSTRACT FROM PUBLISHER]