The transmission link of CAPS navigation and communication system

• Published in: Science China. Physics, mechanics & astronomy mechanics & astronomy, 2009-03, Vol.52 (3), p.402-411
• Main Authors: Cui, JunXia, Shi, HuLi, Chen, JiBin, Pei, Jun
• Format: Article
• Language: English
• Subjects: Antennas; Apertures; Astronomy; Attenuation; C band; CAPS; Classical and Continuum Physics; communication; Communication satellites; Communications systems; demodulation; Global positioning systems; GPS; link; margin; Maritime satellites; navigation; Navigation systems; Observations and Techniques; Parameters; Physics; Physics and Astronomy; satellite; Satellite communications; Satellite navigation systems; Satellite orbits; Signal to noise ratio; Spread spectrum; Spread spectrum transmission; threshold; transmission
• ISSN: 1674-7348; 1672-1799; 1869-1927; 1862-2844
• DOI: 10.1007/s11433-009-0062-9

The Chinese Area Positioning System (CAPS) is based on communication satellites with integrated capability, which is different from the Global Positioning System (GPS), the International Maritime Satellite Organization (Inmarsat) and so on. CAPS works at C-band, and its navigation information is not directly generated from the satellite, but from the master control station on the ground and transmitted to users via the satellite. The slightly inclined geostationary-satellite orbit (SIGSO) satellites are adopted in CAPS. All of these increase the difficulty in the design of the system and terminals. In this paper, the authors study the CAPS configuration parameters of the navigation master control station, information transmission capability, and the selection of the antenna aperture of the communication center station, as well as the impact of satellite parameters on the whole communication system from the perspective of the transmission link budget. The conclusion of availability of the CAPS navigation system is achieved. The results show that the CAPS inbound communication system forms a new low-data-rate satellite communication system, which can accommodate mass communication terminals with the transmission rate of no more than 1 kbps for every terminal. The communication center station should be configured with a large-aperture antenna (about 10-15 m); spread spectrum com- munication technology should be used with the spreading gain as high as about 40 dB; reduction of the satellite transponder gain attenuation is beneficial to improving the signal-to-noise ratio of the system, with the attenuation value of 0 or 2 dB as the best choice. The fact that the CAPS navigation system has been checked and accepted by the experts and the operation is stable till now clarifies the rationality of the analysis results. The fact that a variety of experiments and applications of the satellite communication system designed according to the findings in this paper have been successfully carried out confirms the correctness of the study results.