| dc.description.abstract | Satellite communications were originally developed for scientific and military researches. Nowadays, a number of nations have begun their plans to implement commercial Ka-band satellite systems in the world. These systems will offer multi-media and Internet communications services to individual and corporate customers around the world. ROCSAT-1 is Taiwan’s first scientific satellite. Because its success or failure will affect the future development of satellite technology, it is an object of great concern for the people of Taiwan.
For LEO satellites, systems at low elevation angle suffer not only large free space loss but also great physical attenuations. From the verifications, rain attenuation is the dominant propagation impairment in our experiment. The larger rain rate, the higher frequency or the lower elevation angle is, the larger rain attenuation value will become. Rain attenuation induced in the uplink direction (28.25GHz) are much larger than that induced in the downlink direction (18.45GHz) since the uplink utilizes a high frequency band.
For satellite communication experiments, it is very significant to establish a channel model as close as possible to the real situation. In the past two years, we have successively made some researches on channel characteristics and channel simulations of ROCSAT-1. In this thesis, we make many researches to improve the system performance by various FEC coding schemes: convolutional code, concatenated code, trellis coded modulation, turbo code, and turbo trellis coded modulation scheme. From the results, Turbo trellis coded modulation scheme has better performance, but its decoding structure demands more complexity and takes more time.
We discuss the specifications of ROCSAT-1 link need and how they vary through different paths. For this reason, we choose a real ROCSAT-1 pass as an example to make a complete description of the simulation procedure. Finally, we present the simulation process and give some suggestions from the simulation results. | en_US |