Optical Generalized Spatial Modulation Of High Speed For Atmosphere Laser Communication

Atmospheric laser communication has become a new broadband access technology because of its good security and cost performance.With the rapid increase of data transmission traffic,people put forward higher requirements for the capacity and transmission rate of the atmospheric laser communication system;at the same time,the existence of atmospheric turbulence will seriously affect the effectiveness and reliability of the laser communication system.Optical multiple input multiple output(MIMO)technology can double the channel capacity of the existing system without increasing spectrum resources and transmission power,but the problems of inter channel interference and laser synchronization restrict its application.As a new type of optical MIMO technology,optical spatial modulation(OSM)not only uses traditional digital modulation constellation(signal domain)to transmit information,but also carries information through laser index number(space domain).In this way,the laser is not only the medium of forming wireless link,but also the carrier of information bits.Therefore,it provides an effective measure to improve the transmission rate of the system.In view of this,scholars have carried out extensive research on how to design an efficient opt ical spatial modulation scheme.At present,the research of optical spatial modulation in atmospheric laser communication mainly focuses on the analysis of error rate of OSM in various channel models,but the theory and method about how to improve the transmission rate and the error performance of the system are not mature and perfect.Based on this,this paper focuses on how to improve the speed of traditional OSM on the basis of PPM and PAM which are suitable for IM / DD.At the same time,the idea of antenna selection is introduced to improve the BER performance of the proposed scheme.The details are as follows:(1)Compared with the traditional optical spatial modulation,optical generalized spatial modulation has a great improvement in transmission rate,but its bit error performance is not ideal.In this paper,a double spatial modulation(DSM)scheme is proposed by using PPM and PAM modulation to activate two lasers at a time.At the same time,the upper bound of error rate theory of DSM is derived by using the union bound technique,and the influencing factors of transmission rate and computational complexity are analyzed,and the performance of DSM is compared with that of existing optical spatial modulation.The results show that the DSM scheme can effectively improve the BER performance of the system on the premise of ensuring the high transmission rate of OGSM.(2)Due to the logarithmic growth of the transmission rate and the number of lasers,the utilization of space resources is low.Therefore,a fully optical generalized spatial modulation(F-OGSM)scheme is proposed.In this scheme,the number of active lasers is variable to transmit information,and the linear relationship between the transmission rate and the number of lasers is obtained.At the same time,the algorithm based on channel norm maximization is used to select the active laser,which can effectively improve the BER performance of the system.Finally,the performance of F-OGSM and the existing optical spatial modulation is compared by Monte Carlo simulation.The results show that under the same parameters,the BER of F-OGSM scheme before the laser selection algorithm is slightly higher than that of the existing optical spatial modulation,but its transmission rate is higher.The error p erformance of F-OGSM scheme is better than that of other schemes.