A Simple Two-stage Equalizer With Simplified Orthogonal Time Frequency Space Modulation Over Rapidly Time-varying Channels

Abstract

In this work, we derive a equivalent delay-Doppler channel matrix of the Orthogonal Time Frequency Space (OTFS) modulation that has not been studied in previous literature. It has the similar structure as the banded channel matrix of OFDM systems over rapidly time-varying channels. However, the band in the equivalent channel matrix will no longer spread with the increase of the Doppler spread once the length of maximum channel delay spread and the OTFS frame duration are deter- mined. Furthermore, the equivalent channel matrix can simplify the OTFS modulation in the transmitter side. Incorporating the equivalent channel matrix, we propose a simple two-stage equal- izer in 1 dimensional operations for OTFS modulation. First, the receive signal is equalized using the conventional OFDM single- tap equalizer in the frequency domain. The multipath effects can be removed. In the second stage, another low complexity delay- Doppler domain equalizer is employed to eliminate the effects of the residual interference caused by the Doppler spread with the equivalent channel matrix. The simulation results demonstrate that the proposed method is superior to the conventional single- tap equalizer and full minimum mean squared error (MMSE) equalizer of OFDM systems in terms of BER in high Doppler spread scenarios.

4 pages

References in corpus (1)

• Modulation and Multiple Access for 5G Networks

Cited by in corpus (14)

• Channel Estimation for Orthogonal Time Frequency Space (OTFS) Massive MIMO
• Orthogonal Delay-Doppler Division Multiplexing Modulation
• Orthogonal Time Sequency Multiplexing Modulation: Analysis and Low-Complexity Receiver Design
• OTFS Channel Estimation and Detection for Channels with Very Large Delay Spread
• MIMO-OTFS in High-Doppler Fading Channels: Signal Detection and Channel Estimation
• Message Passing-Based Joint Channel Estimation and Signal Detection for OTFS with Superimposed Pilots
• On OTFS Modulation for High-Doppler Fading Channels
• Orthogonal Time Frequency Space Modulation
• Multiple Access in the Delay-Doppler Domain using OTFS modulation
• Low-Complexity Linear Equalization for OTFS Systems with Rectangular Waveforms
• On the Diversity of Uncoded OTFS Modulation in Doubly-Dispersive Channels
• Message Passing Based Structured Sparse Signal Recovery for Estimation of OTFS Channels with Fractional Doppler Shifts
• Low-complexity and Low-overhead Receiver for OTFS via Large-scale Antenna Array
• Iterative Detection for Orthogonal Time Frequency Space Modulation with Unitary Approximate Message Passing