Simulation And Research Of MIMO-OFDM System Based On Space-time Shift Keying

MIMO-OFDM technology,which combines Multiple-Input Multiple-Output（MIMO）technology and Orthogonal Frequency Division Multiplexing（OFDM）technology,has the advantages of high spectrum utilization,high transmission rate,and high reliability.MIMO-OFDM technology has the advantages of high spectrum utilization,high transmission rate,full utilization of space-time frequency domain resources and the corresponding diversity technology,which can effectively improve the system to multipath effect,interference and noise tolerance,and improve the reliability of the system.However,MIMO-OFDM will generate interference between multiple antennas and the high Peak-to-Average Power（PAPR）inherent in OFDM multi-carrier systems will affect the efficiency of the power amplifier（PA）,resulting in increased energy consumption of the RF system.The traditional MIMO coding technology is not flexible enough in the design of the antenna and the way to obtain the gain,and it is difficult to modify after the design is completed,while the Space-time Shift Keying（STSK）coding technology is based on the Spatial Modulation,and further use the time resources in the Spatial Modulation,the difference is that STSK uses the Dispersion Matrix（DM）for indexing,where the number and size of DMs and the number of activations can be freely and flexibly selected,allowing the STSK scheme to flexibly trade-off the diversity and multiplexing gains in the design.Aiming at the fading problem of STSK single carrier signal in wideband channel,this paper studies STSK-OFDM multi-carrier system and combines direct parallel and indirect serial subcarrier mapping.The experimental results show that the STSK-OFDM multi-carrier system can effectively avoid the fading in the wideband channel,in which the direct parallel mapping helps to avoid inter-symbol interference in the wideband multipath channel more than the indirect serial mapping,and it’s bit error rate has a 1.5d B signal-to-noise ratio improvement in the order of magnitude.In order to further explore the advantages and improvement potential of STSK coding schemes in OFDM systems,this paper compares Spatial Modulation,Generalized Space-time Block Code,Generalized STSK and Frequency-domain Indexed Modulation STSK coding schemes.The experimental results demonstrate that the OFDM system with Frequency-domain Indexed Modulation STSK scheme has a large improvement in the bit error rate compared to Generalized Space-time Block Code,Spatial Modulation,and Generalized STSK at the same order of magnitude with the same normalized throughput.Among them,the Frequency-domain Indexed Modulation STSK improves 7 d B compared to Generalized Space-time Block Code;8.5 d B compared to Spatial Modulation;and 1.8 d B compared to Generalized STSK.For the high PAPR problem in STSK-OFDM system,this paper proposes a Non-linear modulated STSK-OFDM system and theoretically derives the system throughput,channel capacity,gain under frequency selective fading channel and BER.Compared with the ordinary STSK-OFDM system,the Constant-Envelope modulated STSK-OFDM system sacrifices part of the spectrum utilization,but can use non-linear PA without Input Back-off and reduces the RF system energy consumption.The experimental results verify that the Constant-Envelope modulated STSK-OFDM system has PAPR=0d B at modulation index 2πh=2.0,and the bit error rate has 1.9d B and 4d B improvement in the order of 10^-4,compared to₍(7（7）/₀ for generalized STSK and STSK coding,respectively.The cosine modulated STSK-OFDM system reaches the optimal bit error rate interval at modulation index k greater than 0.75,and the PAPR is reduced to 4.1 d B at a complementary cumulative distribution function of 10^-2,with a 0.4 d B improvement in the bit error rate over the₍(7（7）/₀ of the generalized STSK-OFDM system on the order of 10^-4.This paper concludes with a hardware implementation of the non-linear modulated STSK-OFDM digital baseband system on FPGA.