Joint relay selection and power control for robust cooperative multicast in MmWave WPANs We put forward a joint optimization algorithm for relay selection and source u0026 relay power allocations under lineofsight (LoS) and nonLoS mixed conditions for both power saving and robustness enhancement in practical cooperative multicast millimeterwave (mmWave) wireless personal area networks (WPANs). Firstly, a novel beam training protocol capable of overhearing is devised to filter relay candidates with nonLoS links and avoid relays selection for LoS paths through feedback 1bit channel amplitude information (CAI). Secondly, we provide the problem formulation that minimizes the maximum total transmit power consumption under constraints of maximum tolerable outage probability and limited power. As these two problems are coupled together, the formulation is nonconvex with extremely high complexity of finding optimal solution. By introducing relaxation method and Lagrange multipliers algorithm, we propose an optimal approach to reduce complexity while maintaining reasonable performance, and derive a closedform expression of optimal joint relay selection and power allocation. Lastly, simulation results indicate significant improvements both on outage probability and power consumption performances over the existing sum transmit power minimization algorithm.

EnergyEfficient Hybrid Precoding Design for Integrated MulticastUnicast Millimeter Wave Communications with SWIPT In this paper, we investigate the energyefficient hybrid precoding design for integrated multicastunicast millimeter wave (mmWave) system, where the simultaneous wireless information and power transform is considered at receivers. We adopt two sparse radio frequency chain antenna structures at the base station (BS), i.e., fullyconnected and subarray structures, and design the codebookbased analog precoding according to the different structures. Then, we formulate a joint digital multicast, unicast precoding and power splitting ratio optimization problem to maximize the energy efficiency of the system, while the maximum transmit power at the BS and minimum harvested energy at receivers are considered. Due to its difficulty to directly solve the formulated problem, we equivalently transform the fractional objective function into a subtractive form one and propose a twoloop iterative algorithm to solve it. For the outer loop, the classic Bisection iterative algorithm is applied. For the inner loop, we transform the formulated problem into a convex one by successive convex approximation techniques and propose an iterative algorithm to solve it. Meanwhile, to reduce the complexity of the inner loop, we develop a zero forcing (ZF) techniquebased low complexity iterative algorithm. Specifically, the ZF technique is applied to cancel the interunicast interference and the first order Taylor approximation is used for the convexification of the nonconvex constraints in the original problem. Finally, simulation results are provided to compare the performance of the proposed algorithms under different schemes.