Abstract:

Spectral efficiency of faster-than-Nyquist (FTN) and Nyquist systems are investigated. It is proved that the achievable rate of the single carrier FTN (SC-FTN) system with root raised cosine pulse is higher than the single carrier Nyquist system with the same absolute bandwidth. With the inter-carrier interference (ICI), the formula for spectral efficiency of multi-carrier FTN (MC-FTN) is given. For the same roll-off factor, the spectral efficiency of SC-FTN is greater than the single carrier Nyquist. For different roll-off factors, the spectral efficiency of SC-FTN system increases as the roll-off factor decreases. Based on the spectral efficiency formulas and numerical simulation, the corresponding optimal subcarrier spacing for MC-FTN is given in this paper. Even though there is ICI, the spectral efficiency of MC-FTN with optimal subcarrier spacing exceeds the orthogonal Nyquist system.