Latency-Aware Highly-Reliable mmWave Systems via Multi-Point Connectivity
The sensitivity of the millimeter-wave (mmWave) radio channel to blockages is a fundamental challenge in achieving low-latency and highly-reliable connectivity. In this paper we explore the viability of using Coordinated Multi-Point (CoMP) transmission for delay bounded and reliable mmWave systems. We propose a blockage-aware framework for the sum-power minimization problem under the user-specific latency requirements in time dynamic mobile access networks. We use the Lyapunov optimization approach and provide a dynamic control algorithm which transforms a time-average stochastic problem into a sequence of deterministic subproblems. A robust beamformer design is then proposed by exploiting the queue backlogs and channel information that efficiently allocates the required resources by proactively tuning the CoMP subsets from the available remote radio units (RRUs) according to the instantaneous needs of the users. Further to adapt to the uncertainties of the mmWave channel we consider a pessimistic estimate of the rates over link blockage combinations across the CoMP serving set. Moreover after the relaxation of coupled and non-convex constraints via the Fractional Program (FP) techniques a low-complexity closed-form iterative algorithm is provided by solving a system of Karush-Kuhn-Tucker (KKT) optimality conditions. The simulation results manifest that in the presence of random link blockages the proposed methods outperform the baseline scenarios and provide power-efficient highly-reliable and low-latency mmWave communication.