Pilot Reuse Among D2D Users in D2D Underlaid Massive MIMO Systems

TL;DR

This paper investigates pilot reuse in D2D underlaid massive MIMO systems, proposing algorithms to reduce pilot contamination, optimize pilot scheduling and power control, and improve spectral efficiency and system performance.

Contribution

It introduces a pilot scheduling and power control scheme for D2D massive MIMO systems that mitigates pilot contamination and enhances spectral efficiency.

Findings

Pilot contamination can be significantly reduced with the proposed scheduling algorithm.

The pilot reuse scheme outperforms orthogonal training in spectral efficiency.

The algorithms ensure QoS for cellular users while maximizing D2D link sum rate.

Abstract

In a device-to-device (D2D) underlaid massive MIMO system, D2D transmitters reuse the uplink spectrum of cellular users (CUs), leading to cochannel interference. To decrease pilot overhead, we assume pilot reuse (PR) among D2D pairs. We first derive the minimum-mean-square-error (MMSE) estimation of all channels and give a lower bound on the ergodic achievable rate of both cellular and D2D links. To mitigate pilot contamination caused by PR, we then propose a pilot scheduling and pilot power control algorithm based on the criterion of minimizing the sum mean-square-error (MSE) of channel estimation of D2D links. We show that, with an appropriate PR ratio and a well designed pilot scheduling scheme, each D2D transmitter could transmit its pilot with maximum power. In addition, we also maximize the sum rate of all D2D links while guaranteeing the quality of service (QoS) of CUs, and develop an iterative algorithm to obtain a suboptimal solution. Simulation results show that the effect of pilot contamination can be greatly decreased by the proposed pilot scheduling algorithm, and the PR scheme provides significant performance gains over the conventional orthogonal training scheme in terms of system spectral efficiency.