Iterative Channel Estimation And Equalization For High-rate Underwater Acoustic MIMO Communications

The reliable and robust underwater information transmission technology based on the underwater acoustic communication occupies an important position on modern marine exploration.The limited bandwidth resources and severe channel multipath propagation are the main problem for the high-speed underwater acoustic communication technique.The MIMO technique can improve the communication rate within limited bandwidth.The iterative equalization technology can effectively control the channel multipath propagation.In order to satisfy the requirement for the high-speed underwater acoustic communication,we study the high-speed underwater acoustic communication MIMO communication technology with iterative channel estimation and equalization technology.First,we gave the basic framework of the MIMO communication system.For the high-speed underwater acoustic communication requirement,this paper is organized as follows.(1)The analysis of the channel capacity of MIMO communication system.(2)At the known channel,the conventional DFE iterative equalization algorithm has the error propagation;we use the soft information instead of the hard decision to improving the performance.(3)The soft interference cancelation solves the interference between the different transmit information in the MIMO communication.Combining with the Turbo equalization,the SIC-SDFE iterative equalization algorithm is presented.(4)Finally,we study the MIMO communication technology based on the iterative channel estimation and equalization.And the simulation results accord with the theoretic study.The detail contents is organized as follows:(1)The target of the communication rate is 60 kbps/s,under the existing 8-16 kHz underwater acoustic transducers condition,we study the MIMO communication channel capacity on the different configures.1)When the emitter source level is 180 dB,the MIMO system of the 4 transducers and the 4 hydrophones can achieve the target communication rate at the received signal to noise ratio is 5 dB.2)When the emitter source level is 190 dB and the target communication rate is 60 kbps/s,the maximum communication distance can reach 9 meters for the MIMO system with the 16 transducers and the 32 hydrophones.(2)At the random known channel,we simulate the 16 QAM 8×8 MIMO system based on the SIC-SDFE algorithm,its bit error rate can reach 0 when the signal noise rate is 13 dB.(3)Comparing the unknown channel with the known channel,the performance of the system based on the iterative channel estimation decreases about 1dB.(4)When the SNR is 7dB,the bit error rate of BPSK 2×2 MIMO with the iterative channel estimation and SIC-SDFE equalization is reach 0 after 1 iterations.(4)Using the actual measured sound speed profile of Sonhua lake,we simulate the MIMO underwater acoustic channels by Bellhop.Based on the channel,the UWA MIMO communication system based on the iterative channel estimation and SIC-SDFE is verified and analyzed.The study shows that the bit error rate of BPSK 2×2 MIMO system can reduce to 0 when the SNR is 7dB,and 8PSK 2×2 MIMO needs the gain of the 14.5dB.