An Improved Unique Word DFT-Spread OFDM Scheme for 5G Systems

In this paper, we propose a new waveform based on discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S-OFDM), in which the tail of the DFT-S-OFDM symbol contains a fixed sequence, i.e., a unique word (UW). The proposed waveform, called UW DFT-S-OFDM, improves upon both existing zero-tail (ZT) DFT-S-OFDM and UW OFDM schemes by removing the impact of data symbols on the tail of the transmitted signal. This is done by creating a redundant symbol vector that has 1% of the total transmitted energy approximately. As a result, the proposed UW DFT-S-OFDM scheme keeps the advantages of UW OFDM and ZT DFT-S-OFDM such as the circular convolution of the channel without the use of a cyclic prefix (CP), low peak-to-average power ratio (PAPR), and low out-of-band (OOB) emission. In addition, by generating the UW sequence at the input of the DFT process, simpler receiver operation is obtained.