Latency-aware Reliable mmWave Communication via Multi-point Connectivity

Abstract

The sensitivity of millimeter-wave (mmWave) radio channel to blockage is a fundamental challenge in achieving lowlatency and reliable connectivity. In this paper, we explore the viability of using coordinated multi-point (CoMP) transmission for a delay bounded and reliable mmWave communication. We provide an iterative algorithm for the time-average sumpower-minimization problem by solving a system of Karush-Kuhn-Tucker (KKT) optimality conditions. We use the Lyapunov optimization framework and derive a dynamic control algorithm to transform a time-average stochastic problem into a sequence of deterministic subproblems. Furthermore, for the robust beamformer design, we consider a pessimistic estimate of the userspecific rate, assuming that a portion of CoMP links would be blocked during the data transmission phase, while ensuring the average latency requirements. The numerical examples illustrate that in the presence of random blockages, the proposed method outperforms baseline scenarios and results in energy-efficient, high-reliability and low-latency mmWave communication.

Latency Constrained Simultaneous Wireless Information and Power Transfer

“…We consider a SWIPT system with K = 4 UEs being served by a BS equipped with a uniform linear array (ULA) of N t = 8 antennas. For simplicity, we assume the same parameters for all UEs, i.e., noise variance δ 2 k = −50 dBm and σ 2 k = −70 dBm; (8) [11].…”

“…Thus, we use the queue backlogs {Q k (t)} as latency measure, and impose the allowable upper bound {Q th k } for each time slot. Specifically, we consider a probabilistic constraint on user-specific queue length [11], defined as…”

“…First, we provide a dynamic control algorithm, specifically the driftplus-penalty function, using the Lyapunov optimization [10]. Next, the coupled and non-convex constraints are handled via SCA technique [11], [12], and an iterative algorithm, where each step is computed in closed-form expressions, is proposed by solving a system of KKT optimality conditions [13].…”

“…The problem ( 13) is still intractable due to the non-convex SINR expression (13b), and the coupling between the optimization variables {f k (t), ρ k (t)} in constraint (13b) and (13c). Thus, we adopt the SCA framework [11], [12], wherein the non-convex problem ( 13) is recast as a sequence of convex subproblems, and then iteratively solved until convergence. In the following, time index t is omitted for notation brevity.…”

“…To provide a tractable solution for the considered time-average problem, we provide a dynamic control algorithm using the Lyapunov optimization framework [10]. Furthermore, the coupled and non-convex constraints are handled via the Successive Convex Approximation (SCA) technique [11], [12], and a lowcomplexity algorithm, requiring the iterative evaluation of closed-form expressions, is proposed by solving a system of Karush-Kuhn-Tucker (KKT) conditions [13]. The simulation results manifest the robustness of the proposed design to realize a power-efficient SWIPT system for meeting userspecific latency and EH requirements in a dynamic network.…”