Energy-Efficient Joint Congestion Control and Resource Optimization in Heterogeneous Cloud Radio Access Networks

The heterogeneous cloud radio access network (H-CRAN) is a promising paradigm that integrates the advantages of cloud radio access networks and heterogeneous networks. In this paper, we study joint congestion control and resource optimization to explore the energy efficiency (EE)-guaranteed trade-off between throughput utility and delay performance in a downlink slotted H-CRAN. We formulate the considered problem as a stochastic optimization problem, which maximizes the utility of average throughput and maintains the network stability subject to the required EE constraint and transmit power consumption constraints by traffic admission control, user association, resource block allocation, and power allocation. Leveraging on the Lyapunov optimization technique, the stochastic optimization problem can be transformed and decomposed into three separate subproblems that can be concurrently solved at each slot. The third mixed-integer nonconvex subproblem is efficiently solved by utilizing the continuity relaxation of binary variables and the Lagrange dual decomposition method. Theoretical analysis shows that the proposal can quantitatively control the throughput-delay performance trade-off with the required EE performance. Simulation results consolidate the theoretical analysis and demonstrate the advantages of the proposal from the prospective of queue stability and power consumption.

I. Introduction

Recently, the mobile operators have been facing the continuously growing demand for ubiquitous high-speed wireless access and the explosive proliferation of smart phones. Justified by the urgent trend and projecting the demand a decade ahead, the so-called 100 times spectral efficiency (SE) boost and 1000 times energy efficiency (EE) improvement compared with the current fourth-generation wireless systems are required [1]. The increasing demands make it more challenging for operators to manage and operate wireless networks and provide the required quality of service (QoS) efficiently. Therefore, the fifth-generation wireless networks are expected to fulfill these goals by putting forward new wireless network architectures, advanced signal processing, and networking technologies [2].