Mobile association for wireless heterogeneous networks with cooperative relays: optimal framework and implementation schemes

Abstract

Heterogeneous networks improve the spectrum efficiency and coverage of wireless communication networks by deploying low-power nodes on top of the conventional network nodes. In this paper, we consider a heterogeneous cellular network with multiple low-power relay nodes (RN) deployed in each cell using in-band wireless backhaul link between the RN and the base station (BS). The RNs work cooperatively with the BSs on the downlink communication towards the user equipments. Due to the disparity between the transmit powers of the BSs and the RNs, mobile association schemes developed for the conventional homogeneous networks may lead to a highly unbalanced traffic load distribution with most of the traffic being concentrated on the BSs. In this paper, we propose a new mobile association framework for the heterogeneous wireless networks with node cooperation. The proposed framework aims to maximize the network capacity and balance the traffic load among the network nodes. A pseudo-optimal solution is obtained for the proposed mobile association framework using a centralized gradient-descent algorithm. To enable online implementation, we further introduce a distributed algorithm using a pricing mechanism. Numerical results show that a prominent improvement in network capacity can be achieved by the proposed load balancing-based mobile association scheme compared with the conventional counterpart. Moreover, compared with the pseudo-optimal solution, the proposed pricing-based distributed algorithm only suffers a small loss in network capacity and thus can be considered as an efficient real-time implementation alternative.