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Energy and Spectral Efficient Tradeoff for Massive MIMO Enabled Heterogenous Networks with Wireless Backhaul

In this paper, we provide a general framework to investigate the tradeoff between spectral efficiency (SE) and energy efficiency (EE) in massive multiple input multiple output (MIMO) enabled heterogeneous networks (HetNets) with wireless backhaul. Our target is to optimize joint beamforming and power allocation to maximize SE and EE simultaneously, so we formulate it as a multi-objective optimization problem. Based on the weighted Tchebycheff method, we transform the multi-objective optimization problem into a single-objective optimization problem with involving quality of service (QoS) in terms of the minimum rate constraints of each user, the interferences between intra-cell and inter-cell, and capacity-limited wireless backhaul. Since the problem is not convex, we provide a novel iterative algorithm that is a combination of successive convex approximation (SCA) and alternating optimization (AO) to solve it effectively. Both theoretical analysis and numerical results demonstrate that the proposed algorithm can fast converge and the EE-SE tradeoff performance is superior over existing power allocation algorithm.