Multi-Antenna Communication Based On Chaotic Baseband Waveform

Chaos is a class of random like motion in a deterministic nonlinear systems sensitive to initial values,and is considered one of the three most important discoveries in physics during twentieth century.Chaos is widely used in the field of communication because of its unique properties such as initial value sensitivity,randomness,and wide spectrum.With the establishment of chaotic wireless channel capacity theory and chaotic baseband wireless communication system framework,chaos is proved to be able to enhance system performance in wireless communication.Currently,chaotic wireless communication has been studied in various channel conditions for single antenna and demonstrated excellent results.As one of the most important technical tools in wireless communication,multiple antennas have played an important role in wireless communication technology by bringing significant improvement in system reliability and effectiveness through diversity and multiplexing.Compared with single-antenna systems,multiple antennas bring performance gains and also problems such as serious inter-channel interference and diverse fading.How to combine multi-antenna technology with chaos theory to improve the performance of wireless communication system is a very meaningful work.This paper focuses on multi-antenna wireless communication methods based on chaotic spread spectrum communication and chaotic baseband communication,the detailed work is given as follows:Firstly,a multi-antenna differential chaotic keying(MIMO-CSF-DCSK)scheme based on shaped filters is proposed.The scheme first uses the chaotic sequence generated by the chaotic shape forming filter to replace the chaotic sequence generated by Logistic map in the conventional MIMO-DCSK scheme,and improves the BER performance based on the conventional MIMO-DCSK scheme.A matched filter corresponding to the digital chaotic shape forming filter is introduced and combined with the space-time group coding in the multi-antenna system to effectively reduce the system noise and interference between different antenna channels.At the same time,the chaotic signal generated by the chaotic shape forming filter is used as a spreading sequence to carry information,thus transmitting an additional bit stream transmission channel along the way.Secondly,the conventional DCSK methods require half time slot to send the reference signal,which leads to the problems of slow information transmission rate and low channel utilization.To solve this problem,an improved MIMO-CSF-DCSK scheme is proposed using the multi-antenna system with multiple spatial channels,In the proposed configuration,one antenna sends a chaotic signal as the reference signal and the remaining multiple antennas sends the information bearing signal.The system performance of this scheme using two-antenna and four-antenna are analyzed in the paper,respectively,and the system throughput is improved while the system BER is reduced.Thirdly,the time-frequency characteristics of chaotic waveforms under different parameters are studied,and a multi-antenna multi-baseband information coding(MIMO-CQOC)scheme is proposed by combining space-time packet coding and chaotic coding.Among them,spatio-temporal group coding achieves time domain and spatial domain feature,while chaotic coding achieves frequency domain feature by using the quasi-orthogonal property of waveform frequency domain.The combination of two coding method improves the coding efficicency in three dimensions,which improves the system performance.Meanwhile,the receiver side uses the matched filter set and the quadrature filter set simultaneously to decode.The matched filter set reduces the influence of noise and determines the number of different binary bits;the quadrature filter set eliminates the influence of signal interference between different fundamental frequencies to assist the decoding and improve the decoding accuracy.The system performance of the scheme is analyzed when the fundamental frequency parameters are 2,4 and 8 respectively,and the results prove that the system throughput performance is improved and the system BER is reduced with a fixed transmission rate.