QoS-Aware Energy-Efficient Joint Radio Resource Management in Multi-RAT Heterogeneous Networks

A heterogeneous wireless network (HetNet), which combines multiple cooperating radio access technologies in an overlapping structure, is a communication system that has been recognized as an efficient way to meet the increasing traffic demand in broadband wireless networks. In this paper, we exploit the network cooperation in HetNets to propose two joint radio resource management (JRRM) schemes that improve energy savings while satisfying the system quality-of-service (QoS) performance requirements. First, we present an optimal QoS-aware energy-efficient JRRM scheme, which is formulated as a semi-Markov decision process model, and provide the optimal control policy for the HetNet under analysis. Second, we present an implementation-friendly QoS-aware energy-efficient JRRM scheme that utilizes a threshold on the macrocell radio resource occupancy to trigger the switching-on/off procedure of the base transceiver station resources, as well as a load-balancing procedure to minimize the service disruptions that may occur because of radio resource shortage and to reduce power consumption during the HetNet operation. This JRRM scheme is analyzed by means of a multidimensional continuous-time Markov chain model. Third, we devise an algorithm to determine the threshold setting in the implementation-friendly JRRM scheme according to a desirable power saving level that is prespecified by the mobile network operator. Numerical results show that the proposed schemes achieve substantial energy savings while keeping satisfactory performance levels.