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Joint User Grouping and Beamwidth Optimization for Satellite Multicast with Phased Array Antennas

The communication satellite equipped with phased array antennas can produce high power density by narrow spotbeams and thus can achieve high data rates. A large number of narrow spotbeams are required when the satellite provides multicast service for a group of distributed ground users, which limits the system capacity. In this paper, we propose a new satellite multicast scheme as taking advantage of beams with flexible direction and beamwidth generated by phased array antennas. Users are partitioned into multiple groups and an appropriate beam is allocated to each group, where all users in the same group are located in the mainlobe of the beam. It is formulated to jointly optimize user grouping and beamwidth for maximizing the average data rate of satellite and guaranteeing the quality-of-service (QoS) for users. Moreover, we develop an iterative algorithm to solve the problem with low complexity. Finally, simulation results show that our proposed method is superior to other schemes in terms of average data rate.