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