Research On Channel Estimation And Signal Detection Of MIMO-OTFS System Based On Interference Cancellation

Orthogonal frequency division multiplexing(OFDM)modulation scheme is not robust to high Doppler spread time-varying channel and the carrier interference and symbol interference caused by Doppler spread will cause system performance loss in high speed mobile communication scenarios.Orthogonal Time-Frequency Space(OTFS)modulation is an alternative scheme for OFDM,which converts time-varying multipath channels into time-invariant two-dimensional convolutional channel in the delay-Doppler domain,and performs modulation and demodulation in the domain.MIMO-OTFS technology,which combines MIMO and OTFS,has the advantages of both MIMO and OTFS,and has great research value.In this dissertation,the signal detection and channel estimation of MIMO-OTFS system are studied,and the MIMO-OTFS software radio experiment is carried out on the software radio platform to verify the communication performance of OTFS in the real environment.The main contents of this dissertation are as follows:(1)The traditional linear and nonlinear signal detection algorithms in MIMO system are introduced and analyzed,and the algorithms are verified by simulation.Then,the traditional MMSE-OSIC signal detection algorithm based on interference elimination in MIMO system is improved.According to the received signals and the channel transmission matrix,the receiver first calculates the signal to noise ratio(SINR)of each layer of signals and ranks them.Then,the information transfer algorithm detects the group of signals with the largest SINR and then removes it.Then the second layer of signals is detected,and finally all signals are detected in turn.The simulation results show that the improved algorithm has better performance than the original algorithm.(2)Based on the technical characteristics of OTFS,a channel estimation algorithm suitable for MIMO-OTFS system is proposed.This algorithm takes advantage of the characteristic that OTFS needs to load transmitting and receiving pulses in the process of transmitting and receiving,and takes transmitting pulse,channel impulse response and receiving pulse as a whole in the channel estimation.After the channel estimation of the pilot position is calculated by the receiver,the channel estimation of the pilot position is extended to the whole channel estimation by interpolation.In order to eliminate the interference,an iterative process is added to the algorithm in this dissertation,so that the estimated value of the whole channel state information is finally obtained and the proposed algorithm is verified by simulation.(3)The software radio simulation platform is built by Lab VIEW and USRP,the MIMO-OTFS system is designed by Lab VIEW.The communication performance of the OTFS system in the real environment is experimented and analyzed by using Alamouti coding.The experimental results show that the performance of the MIMO-OTFS system is reliable.