Ka-band Satellite Communication Channel Characteristics And Application Of TDMA Rain Fade Countermeasures

With the increase in the demand for a larger capacity of the satellite communications channel, and the ever-growing congestion of the tasks in C and Ku frequency band, there is a constant want of a satellite communication system which can be applied at a higher frequency band with a broader bandwidth and a frequency spectrum of higher efficiency. The traditional C and Ku frequency band satellite communication system can no longer meet the developing needs of various tasks through broadband satellite communications. Ka-band satellite communication system, therefore, for all its advantages, eg. an offer of a large bandwidth ( 3.5 GHz), a huge capacity of communications, a narrow wave beam, a reasonably small terminal size and a possible capacity for more satellites on the orbit plane, will be an inexorable trend in the future satellite communications.However, the Ka-band satellite communication system is now confronted with a great challenge --- it is easily affected by meteorological factors, which, for one time, aroused suspicion among researchers about its realization. Rainfalls, twinkles, as well as atmospheric absorption can all lead to the deterioration of Ka-band field-to-air link channel quality. The present paper, with its emphasis on the effect of rainfalls on the capabilities of satellite communications, discusses in detail the wave-spreading characteristic of Ka-band satellite communication, in accordance with which, a simulation model is built, and besides, a function evaluation is made. Two methods are adopted here: one is analysis and the other emulation.One of the main limitations of Ka-band satellite communication is the great influence by rain fade. So a dynamic countermove must be adopted to guarantee the usableness of satellite link channels. And self-adapted TDMA is a very efficient one. The paper works out solutions for self-adapted TDMA, including the arrangement of the earth station structure and the frame structure, and also the transmission of the system structure and the information about link channel quality. In addition, the paper presents an optimum estimation algorithm for link channel quality in rain fade. According to the algorithm, function of providing number of corrections given by Viterbit codec can be used for estimating BER, and an efficient rain fade estimation model may help calculate the best estimation time, then Eb/No for rain fade channel and the rain fade values can be both estimated.