Mobile Communications Beyond 52.6 GHz: Waveforms, Numerology, and Phase Noise Challenge

TL;DR

This paper explores the evolution of 5G NR physical layer to support beyond 52.6GHz communications, focusing on waveform robustness against phase noise, and proposes enhanced PTRS designs for improved performance at 60GHz.

Contribution

It introduces revised PTRS structures for DFT-s-OFDM and a novel block PTRS for OFDM, extending 5G NR capabilities to higher frequencies with improved phase noise mitigation.

Findings

DFT-s-OFDM is more robust against phase noise than OFDM.

Enhanced PTRS designs improve phase noise compensation.

Supporting beyond 52.6GHz is feasible with proposed waveform modifications.

Abstract

In this article, the first considerations for the 5G New Radio (NR) physical layer evolution to support beyond 52.6GHz communications are provided. In addition, the performance of both OFDM based and DFT-s-OFDM based networks are evaluated with special emphasis on the phase noise (PN) induced distortion. It is shown that DFT-s-OFDM is more robust against PN under 5G NR Release 15 assumptions, namely regarding the supported phase tracking reference signal (PTRS) designs, since it enables more effective PN mitigation directly in the time domain. To further improve the PN compensation capabilities, the PTRS design for DFT-s-OFDM is revised, while for the OFDM waveform a novel block PTRS structure is introduced, providing similar link performance as DFT-s-OFDM with enhanced PTRS design. We demonstrate that the existing 5G NR Release 15 solutions can be extended to support efficient mobile communications at 60GHz carrier frequency with the enhanced PTRS structures. In addition, DFT-s-OFDM based downlink for user data could be considered for beyond 52.6GHz communications to further improve system power efficiency and performance with higher order modulation and coding schemes. Finally, network link budget and cell size considerations are provided, showing that at certain bands with specific transmit power regulation, the cell size can eventually be downlink limited.