An Efficient Resource Allocation Mechanism for Beamhopping Based LEO Satellite Communication System LEO satellite communication network has become a promising approach to provide broadband access to internet service in low infrastructure areas. However, the LEO satellites are generally costconstrained and the relative motion between the earth and LEO satellite is highspeed. As a result, the LEO satellite faces limited onboard resources and changing traffic demand distribution. In this paper, we design a beamhopping based system for LEO satellite communication, where the onboard resources are allocated flexibly according to the traffic demand distribution, which can improve the performance of throughput and onboard resource utilization. Specifically, a beamhopping based LEO satellite communication system is constructed and the resource allocation problem is formulated. Then, we propose a greedy algorithm to resolve it. Evaluation results show that the beamhopping system outperforms the fixed beam system and random beam hopping system in terms of throughput and request satisfied ratio.

Transmit Power Allocation with Connectivity Probability for MultiQoS in Cluster Flight Spacecraft Network In this paper, we investigate the transmit power allocation problem to minimize the average packet error rate at the access point in the cluster flight spacecraft network, which adopts the CSMACA channel access mechanism. First, the node mobility, nodal distance distribution, and probabilistic adjacency matrix were formulated for cluster flight spacecraft network based on twinsatellite mode. Then, the optimizationtheoretic model described the optimized transmit power allocation strategy and its implementation algorithm was proposed. And the problem of minimizing the packet error rate of the cluster flight spacecraft network system can be converted into maximizing the expectation of the binary probabilistic adjacency matrix, i.e., maximizing the sum of the nondiagonal elements in the probabilistic adjacency matrix. Due to discreteness of nodal distance distribution, Monte Carlo method was applied to solve the transmit power allocation problem. Yet importantly, the influence of node transmit power on the QoS performance of cluster flight spacecraft network was simulated and analyzed under the assumption of finite overall network transmit power and low traffic load. Finally, the results show that the pocket error rate increases with the provided traffic load, but the pocket error rate hardly changes with the same traffic load in different sequential time slots of any orbital hyperperiod or in the same time slot of different orbital hyperperiods, and by maximizing the sum of the nondiagonal elements in the probabilistic adjacency matrix, the pocket error rate minimum is achieved for a given total network transmit power at any time slot for cluster flight spacecraft network.