Spectra Effiicent Space Time Coding

Space-time coding technology is an important technology in the field of modern communication.Combined with multi-input multi-output antenna system(MIMO),it can significantly improve the performance of communication systems and resistance to channel fading.With the rapid development of mobile terminal services in recent years,people are increasingly demanding high-speed data transmission in communication systems.How to improve the efficiency of communication services under the limitation of limited spectrum resources is an important issue now.This thesis focuses on the improvement of space-time coding technology.The currently used space-time coding mainly includes the following two space time coding methods :Orthogonal space-time coding(OSTBC)and Quasi-orthogonal space-time coding(QOSTBC).Alamouti space-time coding is the leading example of the QOSTBC.Alamouti coding has a significant effect on resisting channel fading,but there is a disadvantage of signal redundancy in order to obtain spatial domain diversity,resulting in decreasing in spectra efficiency(SE).In order to improve spectrum efficiency of Alamouti coding,this thesis proposes a Spectra Efficient Space Time Coding based on Alamouti(SESTCA).SESTCA scheme includes the choice of two space-time coding methods,first one is Alamouti coding,another is the space-time coding obtained by exchanging the symbol sequences sent by two transmitting antennas in two consecutive time slots of Alamouti coding,so that the transmitter can select two encoding modes based on an index variable.Decoder not only decodes the transmitted symbols,but also decodes the index variables so that the values of the index variables are output as additional binary data.SESTCA scheme allows more data be transmitted without using extra bandwidth,which improves the SE of the system.The simulation results show that BER performance of SESTCA is close to Alamouti under the same signal-noise ratio(SNR),indicating that SESTCA not only has good BER performance,but also improves the SE of the system.Since orthogonal space-time coding is only applicable to systems with only two antennas at the transmitter,in a communication system with many transmitting antennas,QOSTBC is required.QOSTBC also has the disadvantage of signal redundancy,resulting in insufficient SE.In order to improve the efficiency of the quasi-orthogonal coding spectrum,this thesis proposes a Spectra Efficient Space Time Coding based on QOSTBC(SESTCQ).Similar to SESTCA,SESTCQ scheme includes the selection of four quasi-orthogonal space-time coding schemes,and the sending end selects the four quasi-orthogonal coding schemes through index variable.The decoder not only decodes the transmitted symbol,but also decodes the index variable and outputs it as additional data,which outputs more data per unit time and improves SE of the system.The simulation results show that the BER performance of SESTCQ is close to that of general quasi-orthogonal coding under the same SNR.