5G Waveforms for Overlay D2D Communications: Effects of Time-Frequency Misalignment

TL;DR

This paper evaluates the impact of time-frequency misalignment on D2D communications coexisting with 5G networks, analyzing interference and waveform performance to optimize D2D transmission strategies.

Contribution

It demonstrates that synchronizing D2D in time is unnecessary and compares various waveforms' effectiveness under misalignment conditions.

Findings

Interference variations are small despite time misalignment.

Linearly convolved waveforms excel in long transmissions.

OFDM remains competitive for short time windows.

Abstract

This paper analyses a scenario where a Device-To-Device (D2D) pair coexists with an Orthogonal Frequency Division Multiplexing (OFDM) based incumbent network. D2D transmitter communicates in parts of spectrum left free by cellular users, while respecting a given spectral mask. The D2D pair is misaligned in time and frequency with the cellular users. Furthermore, the D2D pair utilizes alternative waveforms to OFDM proposed for 5G. In this study, we show that it is not worth synchronising the D2D pair in time with respect to the cellular users. Indeed, the interference injected into the incumbent network has small variations with respect to time misalignment. We provide interference tables that encompass both time and frequency misalignment. We use them to analyse the maximum rate achievable by the D2D pair when it uses different waveforms. Then, we present numerical results showing what waveform should be utilized by the D2D pair according to the time-frequency resources that are not used by the incumbent network. Our results show that the delay induced by linearly convolved waveforms make them hardly applicable to short time windows, but that they dominate OFDM for long transmissions, mainly in the case where cellular users are very sensitive to interference.