Research On MIMO Transmission Scheme In Telemetry System

As the dominant telemetry system of our country,pulse code modulation/frequency modulation(PCM/FM)has the characteristics of high precision,various forms and adaption to digital technology,which has aroused intensive public interest and research.With the development of aerospace industry,the increases of measurement tasks and telemetry data rates have made the limited telemetry frequency band increasingly crowded.As the major breakthrough of smart antenna technology in wireless communication field,multiple-input multiple-output(MIMO)technology can increase the capacity and spectrum utilizaition of the communication system without increasing the system bandwith.Therefore,in the current thesis,we mainly investigated practical MIMO systems that completely adapted to the current PCM/FM telemetry systems,which could improve the information transmission rate and spectrum utilization in limited telemetry band based on the existing telemetry system.In this thesis,the research background and significance of the MIMO telemetry system was first described.In addition,the development status of telemetry system and MIMO technology were summarized respectively.Then,starting from the telemetry PCM/FM system,the modulation and demodulation principle of PCM/FM telemetry system was analyzed.Finally,based on the telemetry channel model,the key technologies of MIMO telemetry communication system which needed resolved urgently were presented.The main contents and achievements of this thesis are shown below:Based on the MIMO telemetry communication system,the constant amplitude zero auto correlation(CAZAC)sequence with good autocorrelation was selected as the premble and then the corresponding frame structure was designed.On the basis of the premble,an improved rough synchronization method based on S&C algorithm was proposed.By improving the structure of the cyclic prefix,the method helped avoid the “peak platform” effect of traditional S&C algorithm.Then,two commonly used frequency offset estimation methods were studied.The simulation results showed that the frequency offset estimation method based on cyclic prefix had better frequency offset estimation performance in the channel environment.Finally,due to the large doppler frequency shift in the channel environment,a channel estimation method based on the data-aided base expansion model (BEM)was presented.The results showed that the performance of the method is better than that of the traditional channel estimation method.In consideration of the relative maturtity and large strock of traditional telemetry system,a practical MIMO transmission scheme based on the existing PCM/FM telemetry system was proposed.By using the idea of polarization MIMO and spatial multiplexing,space-time coding,spatial modulation and MIMO detection,the information transmission rate and spectrum utilization rate of traditional telemetry system could be improved at a low cost.The simulation results showed that the throughput of the system could be doubled when the PCM/FM telemetry system adopted spatial multiplexing or space modulation technology and the signal to noise ratio satisfied certain conditions.When the PCM/FM telemetry system used space-time coding technology,the anti-error performance of the original system could be improved greatly.