D2D Enhanced Heterogeneous Cellular Networks with Dynamic TDD

TL;DR

This paper analyzes a two-tier heterogeneous cellular network with dynamic TDD and D2D communication, providing an analytical framework to optimize coverage and throughput amid traffic asymmetry and interference.

Contribution

It introduces a novel analytical model for dynamic TDD in HCNs with D2D, evaluating the impact of system parameters on performance and offering design guidelines.

Findings

Coverage probability depends on UL/DL configuration and base station density.

Bandwidth partitioning significantly affects total network throughput.

Optimal D2D access balances coverage and network capacity.

Abstract

Over the last decade, the growing amount of UL and DL mobile data traffic has been characterized by substantial asymmetry and time variations. Dynamic time-division duplex (TDD) has the capability to accommodate to the traffic asymmetry by adapting the UL/DL configuration to the current traffic demands. In this work, we study a two-tier heterogeneous cellular network (HCN) where the macro tier and small cell tier operate according to a dynamic TDD scheme on orthogonal frequency bands. To offload the network infrastructure, mobile users in proximity can engage in D2D communications, whose activity is determined by a carrier sensing multiple access (CSMA) scheme to protect the ongoing infrastructure-based and D2D transmissions. We present an analytical framework to evaluate the network performance in terms of load-aware coverage probability and network throughput. The proposed framework allows to quantify the effect on the coverage probability of the most important TDD system parameters, such as the UL/DL configuration, the base station density, and the bias factor. In addition, we evaluate how the bandwidth partition and the D2D network access scheme affect the total network throughput. Through the study of the tradeoff between coverage probability and D2D user activity, we provide guidelines for the optimal design of D2D network access.