SFFT-Based OTFS Communication System Robust to High Doppler and Long Delay Channel

The beyond 5th generation (B5G), the next generation mobile communication, has more requirements than the current generation cellular system. For example, Spectral efficiency, peak data rate and mobility it is. Of these requirements, Orthogonal Time Frequency Space (OTFS) has been proposed as a waveform design study to support mobility. OFDM used in 5G and 4G has a weak point in high speed environment. When the frequency shift occurs due to the Doppler effect, orthogonality between subcarriers of OFDM is broken and performance is degraded. To compensate for this, a complex Doppler compensation algorithm is required, which leads to an increase in complexity. OTFS processes signals in two dimensions in the delay-Doppler domain through the Symplectic Finite Fourier Transform (SFFT). It is compatible with conventional OFDM and can be used as pre-coder and post-coder to effectively handle Doppler without complicate compensation algorithms. This paper evaluates and compares the performance of OFDM and OTFS in high Doppler and time delay environments. As a receiver, we used MP detector proposed for OTFS. The performance is similar to OFDM at low SNR, and the performance is noticeably better than OFDM at high SNR.