Multiplexing Reference Signals and Data in a DFT-s-OFDM Symbol

In this paper, we consider the transmission of DFT spread OFDM (DFT-s-OFDM or SCFDM or SC-FDE) for a cellular uplink, and address the problem of multiplexing reference signals (RS) and data within a single DFT-s-OFDM symbol. Traditionally, RS and data information are transmitted in a time-division-multiplexed fashion with dedicated symbols for RS and data. Different from the traditional approach, multiplexing RS and data within a single DFT-s-OFDM symbol enables mechanisms to transmit short uplink transmissions containing only a single DFT-s-OFDM symbol. This finds applications in the upcoming 3GPP NR systems which have designed short uplink control transmissions for latency constrained applications and for embedding phase tracking reference signals in the uplink transmissions of mmWave systems. A naive approach to multiplex RS and data in a single symbol might harm the single carrier property of DFT-s-OFDM symbol leading to peak-to-average power ratio (PAPR) problems. Therefore, there is a trade-off between performance and PAPR. In this paper, we optimize this trade-off by exploiting the structural properties of discrete Fourier transform (DFT), and propose a novel idea to multiplex RS and data involving frequency domain RS assignment and time domain redundancy. Numerical results are presented to show the efficacy of the proposed design.