A flexible hybrid waveform

Abstract

Cellular systems of fifth generation (5G) require a waveform with flexible guard interval length along with a low power consumption. Different cyclic prefix (CP) durations in long term evolution (LTE) result in loss of orthogonality between transmitted symbols and cause interference. In addition, CP-based waveforms consume more power for CP part. “Zero tail DFT-spread OFDM” (ZT DFT-s-OFDM) and “DFT-spread zero word OFDM” (DFT-s-ZW-OFDM) have been proposed recently with flexible guard intervals as a portion of the modulated signal. However, ZT DFT-s-OFDM suffers from intersymbol interference because of imperfect zero tails. On the other hand, although DFT-s-ZW-OFDM has a superior performance in multipath channels, it consumes more power than ZT DFT-s-OFDM. In this paper, we utilize the similarity between the transceivers of these two waveforms to propose an orthogonal hybrid waveform. The hybrid waveform has high flexibility in order to control the symbol power and bit error rate (BER) performance of the system along with having flexible guard interval. The complexity of the proposed hybrid waveform is the same as ZT DFT-s-OFDM and DFT-s-ZW-OFDM.