| Summary: | 碩士 === 國立清華大學 === 電機工程學系 === 88 === Abstract
In the past two years, two members of our lab, Le-Gen Shi and Pei-Kai Liau, have successively made some researches on channel characteristics and channel simulations of ROCSAT-1. Thanks to Shi and Liau, the prototypes of simulation model including rain loss evaluation, noise power calculation, and analysis of FEC performance etc., are established. However, when examining the proposed simulation model, we found that some efforts can be made to make the model closer to the reality. The refinement to the old model is the objective of this thesis.
First of all, the high rate modem of ground terminal, CM701, provides a protection scheme comprising of Reed-Solomon code and soft-convolutional code to protect the input sequence. The coding rate of Reed-Solomon code depends on the input data rate (symbol per second), but the old model does not take this into account. Besides, the old model adopted a less-efficient hard-convolutional codec. Second, since ROCSAT-1 is a LEO satellite, an accurate description of relative motion between ROCSAT-1 and the ground terminal is very important. The modified model uses real orbit data and is hence believed to be more authentic. Third, it is believed presently that the characteristics of rain attenuation in Ka-band are regional. Therefore, a rain model with input parameters in accordance with Tainan’s weather conditions is helpful. Fourth, the old simulation model does not consider the effect of receiving system. In the receiving system, each cascading device including cables induces noise and hence affects the overall performance.
In this thesis, how to improve the old model based on aforementioned items is introduced in detail. Finally, we present the simulation process and give some suggestions from the simulation results.
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