Resource Allocation for Device-to-Device Communications Underlaying Heterogeneous Cellular Networks Using Coalitional Games

Heterogeneous cellular networks (HCNs) with millimeter wave (mm-wave) communications included are emerging as a promising candidate for the fifth generation mobile network. With highly directional antenna arrays, mm-wave links are able to provide several Gbps transmission rate. However, mm-wave links are easily blocked without line of sight. On the other hand, device to device (D2D) communications have been proposed to support many content-based applications and need to share resources with users in HCNs to improve spectral reuse and enhance system capacity. Consequently, an efficient resource allocation scheme for D2D pairs among both mm-wave and the cellular carrier band is needed. In this paper, we first formulate the problem of the resource allocation among mm-wave and the cellular band for multiple D2D pairs from the view point of game theory. Then, with the characteristics of cellular and mm-wave communications considered, we propose a coalition formation game to maximize the system sum rate in statistical average sense. We also theoretically prove that our proposed game converges to a Nash-stable equilibrium and further reaches the near-optimal solution with fast convergence rate. Through extensive simulations under various system parameters, we demonstrate the superior performance of our scheme in terms of the system sum rate compared with several other practical schemes.

I. Introduction

With the increasing proliferation of mobile devices with high capabilities and intelligence, the global mobile traffic is expected to experience a remarkable and continuous growth in the next few years. As predicted by Cisco, the traffic generated from wireless and mobile devices is expected to constitute a major percentage of the total internet protocol (IP) traffic by 2020. It is also estimated that the number of devices accessed to IP networks will be three times of the global population in 2020 and the mobile traffic will grow at an annual rate of 53% until 2020 [1]. At the same time, the millimeter wave (mm-wave) has huge bandwidth, and therefore, much higher network capacity can be achieved [2]. There are already several standards defined for indoor wireless personal area networks (WPANs) or wireless local area networks (WLANs) in the mm-wave band, such as ECMA-387 [3], IEEE 802.15.3c [4], and IEEE 802.11ad. Thus, in order to keep up with the explosive growth of mobile devices and data traffic, one key enabling solution is to exploit HCNs in both the cellular band and the mm-wave band.