Establishment of Low-Cost Microsatellite Ground Station and Data Broadcasting Transmission with Error Code Correction

• Main Authors: Hui-Ping Liu, 劉惠平
• Other Authors: Fei-Bin Hsiao
• Format: Others
• Language: en_US
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/26590215115220768223

碩士 === 國立成功大學 === 航空太空工程學系 === 87 === As the technology develops, the microsatellites which work simply for the experimental purposes now are getting more and more practical. Nowadays there are already many Earth-orbiting satellites providing telemetry, remote sensing, scientific payload experiments and amateur digital packet communication services. Due to its short term design period and low manufacture cost, the development of microsatellite technology has been encouraged by many countries. This paper hence studies how to establish a low cost ground station through the analysis of data uplink and downlink, phase designing, building, system integration and operation. In addition, the downlink broadcasting quality affected by Doppler shift effect and timing accuracy will also be investigated. Due to fast growing usage of microsatellite data broadcasting, the quality of data transmission has become a very important issue. Due to interference from the amateur radio band and microsatellite's low transmitting power, the broadcast data can frequently be distorted. As the improvement from the frequency and modulation technique for amateur radio has widely been studied, this paper explores the forward error correction technique, called convolutional coding, to be incorporated with the transmission data packet of AX.25 UI Microsatellite Broadcasting Protocol in VHF 144MHz and UHF 430 MHz bands by using AFSK and BPSK digital modulation techniques. Then the present microsatellite broadcasting experiments will be simulated by two ground stations. The transmitted data are then decoded by the maximum likelihood decoding method, or called Viterbi algorithm, to enhance the broadcasting quality. From the experimental results, the performance of data coding and uncoding will be evaluated under the conditions of transmission rate, frequency and modulation techniques. As the usage of the Convolutional Coding will increase the data volume to the double, the compromise between the increased data volume and coding performance will also be discussed. After the employment of the convolutional coding, the results clearly show the increase of the transmission data volume due to its less redundancy and significant improvement of the bit error rate under a number of amateur radio frequency bands tested. This ascertains the merit of the present system applicable for use in the real harsh environmental data transmission.