Doppler based adaptive control for LEO satellite communications systems
Zhong Ye, G.J. Saulnier, Alireza Seyedi, Michael J. Medley · Space Technology Conference and Exposition · 1999
Wireless communications systems in a tactical environment must be able to function effectively in a channel characterized by multipath fading and interference. Additionally, current and future communications requirements will necessitate the transmission of many different types of information with a wide range of data rates over these wireless links. Adaptive signaling is a powerful way to. design a robust system across such broad range of channel conditions because the system will not have to be designed for the worst-case scenario and system resources can be utilized more efficiently. System parameters such as signaling rate, transmit power, modulation format, coding rate, etc. can all be adaptively controlled to achieve the goal of maximizing network throughput while maintaining the desired quality of service. In this paper, we discuss the processing of Doppler information in a LEO satellite communications system to generate information for the adaptive control of signaling parameters. We analyze the link margin of a LEOS link that is characterized by free space loss, multipath fading and interference. A Doppler based adaptation algorithm is proposed which allows the estimation of the mobile terminal received signal strength and, subsequently, the adaptive control of the system parameters. Implementation issues for combining this adaptive system with various multiple access schemes are presented and it is shown that the desired system performance can be maintained across a large dynamic range of signal strength.