Energy-efficient beam scheduling for orthogonal random beamforming in cooperative networks

Abstract

In this paper, we study a joint beam and user scheduling problem in a cooperative cellular networks utilizing orthogonal random beamforming technique. This paper aims to minimize total base stations' average energy expenditure while ensuring finite service time for all traffic arrivals in a given set. We leverage Lyapunov optimization technique to transform original long-term problem into short-term modified max-weight problem without knowledge of future network states such as traffic arrivals. We introduce a controllable parameter which manipulates energy-delay tradeoff in our system as well. Since provided short-term problem is combinatorial and nonlinear optimization problem, we are inspired by a greedy algorithm to design near-optimal joint beam and user scheduling policy, namely BEANS. We prove that proposed BEANS {\em (i)} ensures finite service time for all traffic arrival rates within close to $\frac{1}{2+\varepsilon}$ capacity region and all (energy-delay) tradeoff parameters thanks to submodular characteristics of the objective function, and {\em (ii)} attains finite upper bounds of average energy consumption and average queue backlog for all traffic arrival rates within close to $\frac{1}{4+\varepsilon}$ capacity region and all tradeoff parameters. Finally, via extensive simulations, we compare the capacity region and energy-queue backlog tradeoff of BEANS with optimal and baseline algorithms, and show that BEANS attains x\% of energy saving for the same average queue backlog compared to the algorithm which does not take traffic dynamics into considerations.