Spatial Peak Cancellation for Uplink Radio Access: Processing Methods and Performance

Abstract

High peak-to-average-power ratio (PAPR) is an inevitable challenge in orthogonal frequency-division multiplexing (OFDM) based networks, known to be particularly harmful to efficient utilization of practical power amplifiers (PAs). To preserve the waveform quality, PA back-off can be introduced which, however, directly limits the potential uplink (UL) coverage. This paper proposes a novel PAPR reduction method, by transmitting a peak-cancellation signal (PCS) spatially-precoded to the frequency resources within the operating channel, without introducing any overheads or receiver side interference. The proposed approach can be applied to codebook-based and non-codebook-based transmissions, while also allows for extending the PCS frequency allocation towards neighboring physical resource blocks (PRBs) without interference to other users. Extensive numerical results are provided, conforming with the 3GPP 5G NR transmitter requirements, while also incorporating realistic uplink PA models. The obtained numerical results at FR1 reveals up to 2.6 dB net gain in the effective uplink link budget via using the novel PCS, compared to the plain legacy OFDM signal. Such link budget gains translate to substantial uplink coverage improvements, which can be one major asset in future network deployments towards the 6G era.