Satellite Resources And Performance Optimization Techniques Based On Channel Quality

Satellite communication is regarded as an important way of global communication and it has advantages of wide coverage, great data transmission, no time restriction and globally seamless connections. In Low Earth Orbit (LEO)-ground communication, data can’t be transmitted in real time in the case of unsmooth communication between satellites and their associate ground stations. In order to improve the timeliness of data transmission in LEO satellites, up to now, Geostationary Satellite Communication (GEO) system is used to relay data to ground stations. Because of limitations of satellite resources such as channel, rate etc., it is an important content to reasonably and effectively manage satellite resources, and to increase the utilization in GEO-LEO satellite communication. It is also a hot topic to improve the throughput performance in GEO-ground communication.Two kernel issues of GEO-LEO satellite resources management:channel allocation and traffic flow control, are investigated in this dissertation. The throughput performance and channel quality monitoring technology for GEO-ground communication are also discussed. The main innovations of this dissertation can be summarized as follows:(1) A satellite channel allocation algorithm with comprehensive weights is proposed for the problem of channel allocation in GEO-LEO satellite communication. Several parameters, including satellite channel quality, data communication time, satellite remaining storage capacity and satellite task level, are assigned with different weights to determine the LEO satellite priority. Channel resources could be allocated to LEO satellites with higher priority level first so as to reduce data loss. This algorithm sets constraint conditions initiating calls and preempting channels respectively for LEO satellites to avoid frequent preemption, so that channel utilization could be enhanced and the data integrity and reliable transmission requirements are met.(2) A new method (non-cooperative Nash game, NCNG) is proposed for the management of traffic flow control in satellite communication based on channel quality. According to the "non-cooperative" relationship among LEO satellites, a revenue function is established in GEO-LEO satellite communication network based on channel quality, throughput, and propagation delay across satellite link. The Nash equilibrium solution is obtained by using an iterative method, and its existence and uniqueness are proved by theoretical analysis. The simulation results show that the Nash equilibrium solution has optimized the throughput and delay performance of the system, which satisfies the maximization of system payoffs function.(3) A variable frame length transmission method is proposed to optimize throughput performances in GEO-ground communication. An optimal frame length is utilized for communications in different cases of channel qualities, to obtain maximum throughput performances in this system, and Ka-band throughput performance is also analyzed. Furthermore, according to the results of throughput performance in practical project, a transmission frame length design method is proposed. Basing on mean square error criterions, a transmission frame length is determined for each channel bit error rate interval in this method, and thus the amount of frame length could be limited. Simulation results show that the novel design of actual frame length in practical project not only enhances system throughput, but also reduces the difficulty of system utilities.Finally, the length of monitoring sequence could be designed for satellite communication channels with low signal-to-noise ratio by this method. The optimized length not only meets the requirements of real time, but also increases the acquisition probability and decreases acquisition time by the receiving terminals.