Coordinated Tethering for Multi-RAT Cellular Networks: An Algorithmic Solution and Performance Analysis

Abstract

The radio resources management in multi-radio access technology (multi-RAT) heterogeneous networks plays a dominant role in satisfying the high data rates of current and future applications. With the WiFi technology being the spearhead of the wireless local area networks (WLAN)s, the exploitation of already deployed WLANs (e.g., WiFi access points (AP)s) has attracted considerable attention, as an efficient and practical method to improve the performance of wireless networks. Based on the coordinated tethering concept, we introduce a purely wireless heterogeneous network deployment, where cellular and WLAN radio resources are optimally coordinated towards the universal maximization of user throughput. The wireless users are instructed by the eNB about their role in the network (normal user or AP) and the access technology they have to employ. Important performance metrics of the proposed hybrid scheme, including the bit error probability, the ergodic capacity and the average signal-to-interference-plus noise ratio (SINR), are theoretically studied and closed form expressions are derived for the single-user case with multiple interferers, for both identical and non-identical fading conditions. Also, based on the general multi-cellular hybrid WLAN/Cellular concept, we first propose an intercell interference minimization approach. Then we present a novel scheme for achieving frequency reuse equal to one within a single macro-cell, under specific performance criteria and constraints, that guarantee the overall cell's or the individual user's quality-of-service requirements. For the latter case we consider two optimization problems that aim at the overall cell's SINR maximization or at the minimum user's SINR maximization. For all optimization problems, we propose fast greedy solutions. Numerical results and simulations show that the proposed wireless architecture may offer significant performance gains in the presence of multiple interferers, compared to a conventional cellular network.