SINR Analysis of Different OFDM-Inspired Waveforms Over Doubly Dispersive Channels

Wireless channels generally exhibit dispersion in both time and frequency domain, known as doubly selective or doubly dispersive channels. To combat the delay spread effect, multicarrier modulation (MCM) such as orthogonal frequency division multiplexing (OFDM) and its universal filtered variant (UF-OFDM) can be employed, leading to a simple per-subcarrier one tap equalization. The time-varying nature of the channel, in particular, the intra-multicarrier-symbol channel variation induces spectral broadening and thus inter-carrier interference (ICI). Most existing works address both effects separately, focusing on the one effect while ignoring the respective other. This paper considers both effects simultaneously for cyclic prefix (CP)-, zero padded (ZP)- and universal filtered (UF)-based OFDM with a simple one tap equalization, assuming doubly dispersive wireless channel model. For this general channel model, we show that the independent (wide sense stationary uncorrelated scatter, WSSUS) selectivity in time and frequency domain starts to intertwine in contrast to the ideal cases with single selectivity. We derive signal-to-interference-plus-noise ratio (SINR) in closed form for arbitrary system settings and channel parameters, e.g., bandwidth, delay- and Doppler-spread. With the SINR analysis, we compare the three MCM schemes under different channel scenarios.