DFT-Spread OFDM with Frequency Domain Reference Symbols

TL;DR

This paper introduces a flexible DFT-s-OFDM scheme with frequency domain reference symbols for 5G, enabling shared reference symbols between DFT-s-OFDM and OFDM, reducing interference and power ratio.

Contribution

It proposes a novel puncturing method to embed reference symbols in DFT-s-OFDM, allowing shared use with OFDM and low-complexity interference mitigation.

Findings

Reduces error floor caused by puncturing.

Achieves lower peak-to-average-power ratio than OFDM.

Supports flexible 5G use cases with shared reference symbols.

Abstract

The fifth generation (5G) wireless standard will support several new use cases and 10 to 100 times the performance of fourth generation (4G) systems. Because of the diverse applications for 5G, flexible solutions which can address conflicting requirements will be needed. In this paper, we propose a solution which enables the use of discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-s-OFDM) and OFDM, which address different requirements, using a common reference symbol (RS) design. In this solution, the DFT-s-OFDM symbol contains RSs in the frequency domain that may be shared by a subsequent OFDM symbol. The proposed scheme is generated by puncturing the output of a DFT-spread block and replacing the punctured samples with RSs in frequency. We prove that puncturing the interleaved samples at the output of the DFT-spread operation equivalently introduces a periodic interference to the data symbols at the input of the DFT-spread operation. We show that the interference due to the puncturing can be removed with a low-complexity receiver by exploiting the zeros inserted to certain locations before the DFT-spread block at the transmitter. Simulation results support that the proposed scheme removes the error floor caused by the puncturing and achieves lower peak-to-average-power ratio than OFDM.