An Evolutionary Game for Mobile User Access Mode Selection in Sub-6 GHz/mmWave Cellular Networks

By utilizing the combination of two powerful tools i.e., stochastic geometry (SG) and evolutionary game theory (EGT), in this paper, we study the problem of mobile user (MU) mode selection in heterogeneous sub-6 GHz/millimeter wave (mmWave) cellular networks. Particularly, by using SG tools, we first propose an analytical framework to assess the performance of the considered networks in terms of average signal-to-interference-plus-noise (SINR) ratio, average rate, and mobility-induced time overhead, for scenarios with user mobility. According to the SG-based framework, an EGT-based approach is presented to solve the problem of access mode selection. Specifically, two EGT-based models are considered, where for each MU its utility function depends on the average SINR and the average rate, respectively, while the time overhead is considered as a penalty term. A distributed algorithm is proposed to reach the evolutionary equilibrium, where the existence and stability of the equilibrium is theoretically analyzed and proved. Moreover, we extend the formulation by considering information delay exchange and evaluate its impact on the convergence of the proposed algorithm. Our results reveal that the proposed technique can offer better spectral efficiency and connectivity in heterogeneous sub-6 GHz/mmWave cellular networks with mobility, compared with the conventional access mode selection techniques.

I. Introduction

Future wireless networks, namely beyond fifth generation (B5G) and sixth generation (6G), are required to handle and accommodate a diverse set of both static and mobile end-user devices (e.g., remote sensors, unmanned aerial vehicles and autonomous cars), designating the support of mobility as a fundamental aspect of wireless networks. Moreover, this unprecedented number of connected devices with such diverse requirements is also contributing to the tremendous growing demand for network scalability, latency, and spectral efficiency (SE) [1], [2]. In order to meet this explosive throughput demand of future wireless connectivity, there has been an increasing interest in the synergy of network densification technique by using small cells (SCells) and the millimeter-wave (mmWave) communications [1], [2]. Initially, the concept of network densification refers to the massive deployment of SCells (such as femptocells and picocells) by overlaying the conventional sub-6 GHz networks. Such heterogeneous network (HetNet) architectures can provide high throughput to the static users, but may significantly deteriorate the performance of mobile (i.e., moving) users (MUs). Indeed, the higher number of randomly deployed cells leads a MU to experience an increased number of handovers at cell boundaries, thereby resulting in potentially significant signaling overhead among the base stations (BSs) and MUs, compromising the HetNets performance [3].