Research On Key Techniques Of Wireless Channel Sounding

In wireless communication, channel conditions directly affect the performance of communication system. As a basic subject in wireless communication, channel sounding is an indispensable part in the design of communication system. Hypersonic flight technology, as a hot topic in the field of modern aerospace, has important strategic significance and high application value. Measurement and control in communications are key technologies of hypersonic flight field. It is the technical assurance to ensure the hypersonic flight communication. The channel characteristics of hypersonic mobile environment are the basis of measurement and control in communication system design, and the research of the hypersonic mobile channel characteristics is of great significance.Hypersonic mobile channel changes very quickly with large Doppler frequency shift because of big plasma sheath channel loss. These features lead to severe challenges for channel sounding. This paper mainly introduces research on the channel sounding of the hypersonic mobile channel. The concrete work is as follows:First of all, this paper discusses the basic characteristic of the hypersonic mobile channel, and some of hypersonic communication channel parameters are analyzed in detail. At the same time, the characteristics of the large and small scale parameters of hypersonic mobile channel were described. The large scale parameters mainly express the path loss of scattering channel. The small scale parameters including the time delay parameters and Doppler parameters, describe the frequency selective fading and time selective fading of channel in detail.Then, according to the main characteristics of hypersonic mobile channel, channel sounding schemes based on CAZAC sequence(sliding correlation and SAGE algorithm) and pulse compression channel measurement scheme based on chirp sequence are discussed firstly. Based on the above schemes, a new kind of channel sounding scheme is introduced to achieve the requirement of hypersonic mobile channel sounding(pulse compression channel measurement method based on CAZAC sequence).In large scale parameter information extraction, in order to lower the noise effect, this paper puts forward the SNR estimation of received signal to estimate signal power. Use the estimates of the signal power to obtain the statistical features of the large scale of channel. In small scale parameter information extraction, the channel delay power spectrum and Doppler shift information was extracted, and through strict calculation simulation of the performance, the algorithm is analyzed. Based on the use of GPS seconds pulse, by optimizing design of the frame structure, the absolute time delay of signal transmissions measured successfully.Finally, using the proposed channel sounding method, field measurement on plasma sheath of simulator was carried. Using the local CAZAC sequence cycle processing technology, the large scale parameter information and small scale parameter information of the plasma sheath are extracted, improving the measurement accuracy of the channel amplitude and phase changes. From field experiment results, the feasibility and effectiveness of the proposed parameters extracted method and the pulse compression measurement based on chirp signal have been verified.