CP Optimization for Multi-numerologies F-OFDM in MIMO System

Abstract

Filtered-orthogonal frequency division multiplexing (F-OFDM) is a potential waveform which uses sub-band filtering to support multi-numerologies in the future 5G systems. It is a future trend to combine F-OFDM with MIMO to further improve the system capacity. However, when employing different numerologies, a long filter length is needed to suppress severe inter-user interference (IUI) caused by various symbol duration in time domain, which causes inter-symbol interference (ISI) and inter-carrier interference (ICI) at the same time. Longer CP is helpful to resist the effect of multipath and filter responds but will waste more time resource. In order to reduce ISI and ICI while improving the spectrum efficiency, we propose a CP optimization model based on theoretical derivation of ISI, ICI and IUI for downlink MIMO F-OFDM system. The simulation results show that the ISI and ICI decrease as CP gets longer, while the spectrum efficiency is improved based on the proposed CP optimization model and outperforms traditional OFDM.