Study On Microwave Link Budget For Land Mobile Satellite Communication Systems Considering Multipath

thoroi~hly studied for Land Mobile Satellite Communications (LMSC), which are being developed rapidly in world. Firstly, this paper summarizes the current situation and develo~ment of mobile satellite communications. Afterwards, classification of mobile satellite communications as well as technical parameters of several main LMSC systems being researched and mabufactured is introduced. Meanwhile, the author analyzes channel characteristics of land mobile satellite systems, of which microwave signal rnultipath fading and shadowing effect are emphasized. And, those propagation experiments which were conducted by relative organizations abroad with the expectation to understanding propagation peculiarities for LMSC are also summed up. General, both the microwave signal fading depth of signal and its rate of change must be investigated in order to describe channel characteristics of LMSC systems. While channel models provide information on fading depth, Level Crossing Rate (LCR) and III Average Fade Duration (AFD) are quantities that indicate the signal changing rate. Based on thoroughly investigating several empirical regression models and probability distribution models suggested by foreign and domestic experts, a new mobile satellite channel model is proposed, which surmounts such shortage of traditional models as limitation to application areas and obscure physics significance, for the model considers richly different effects that environments such as urban, rural and open areas may have on channel qualities and satellite signal. The model treats the change of channel properties as three different states on according to the extent to which the line梠f梥ight signal is shadowed. Meanwhile, the influence elevation angel has on the line梠f梥ight signal is shadowed. Meanwhile, the influence elevation angel has on the model parameter is also discussed, which makes the model more rational. Formula of Level Crossing Rate and Average Fade Duration fit for different environments and satellite angel are derived. The value of correlation coefficient between Changes caused by Mutipath and Shadowing effect is also given here. The sta駍tics for LCR and AFD are studied through mathernaticaj calculations and some useful conclusions are drawn in this paper.