Asynchronous Performance of Circularly Pulse-Shaped Waveforms for 5G

The fifth generation of wireless networks (5G) necessitates the use of waveforms with loose constraints on synchronization in multiuser scenarios. Also, carrier aggregation, as a way to better utilize the spectrum in 5G, needs a waveform with low out-of-band (OOB) emissions. Generalized frequency division multiplexing (GFDM) and circular filter bank multicarrier (C-FBMC) are two candidate waveforms that fulfill these requirements. Both GFDM and C-FBMC operate based on circular convolution, and use cyclic prefix to combat channel response. Because of obvious reasons, we refer to these waveform as circularly pulse-shaped. In this paper, we develop an analytical technique for examining the OOB emissions and multiuser interference (MUI) in circularly pulse-shaped waveforms. To stay focused, the study in this paper is limited to C-FBMC modulation. However, the approach we take is trivially extendable to other waveforms (including GFDM) as well. We derive equations that quantify OOB emissions and MUI. Our analysis allows us to identify the source of OOB emissions and MUI. This leads us to quantify the methods proposed by other researchers to decrease OOB emissions and MUI. Moreover, we quantify the impact of signal windowing at the transmitter and receiver in reducing OOB emissions and MUI, respectively.