Multibeam Mobile Satellite Communications System Research Articles

A traffic-awareness dynamic resource allocation scheme based on multi-objective optimization in multi-beam mobile satellite communication systems

Mobile satellite communication systems play an important role in space information networks. They mostly operate at the L or S band and have multiple beams efficiently reusing the limited spectrum. Advanced technologies, such as beamforming, are used to generate numerous beams through multiple feeders, and each beam’s power allocation is correlated and constrained. Frequency reuse among multiple beams results in co-channel interference issue, which makes bandwidth allocation among multiple beams coupled. It is a challenging topic to optimize the resource allocation in the real-time service traffic. In this article, a new multi-objective programming scheme is used to solve the dynamic resource allocation problem, guaranteeing high quality-of-service for multiple services of different priorities. Since the dynamic resource allocation problem is formulated as NP-hard, a new traffic-aware dynamic resource allocation (TADRA) algorithm is proposed. This algorithm is proved to be optimal in terms of the Pareto-front under constraints of co-channel interference and onboard transmit power. Simulation results show that the trade-off is well balanced between the call completion ratio in high priority and the throughput for video and data services in medium and low priorities. Additionally, it is shown that the new multi-objective programming scheme, based on the traffic-awareness dynamic resource allocation algorithm, can rapidly achieve the Pareto-front solutions and reduce the computing complexity to a large extent.

Communication Capacity and Quality Enhancement Using a Two-Layered Adaptive Resource Allocation Scheme for Multi-Beam Mobile Satellite Communication Systems

To obtain large capacity, high quality mobile satellite communication systems in the future, we must use a multi-beam that can cope with extremely high levels of frequency reuse. This paper describes a novel resource allocation algorithm for multi-beam satellite communication systems that can dynamically adapt to maximum communication capacity without compromising quality. The algorithm combines two resource allocation schemes that enable it to contend with the ever-changing user distribution and inter-beam interference conditions. The first scheme optimizes the resources amongst beams. To minimize interference, the optimal constraint conditions are clarified when all clusters share and occupy the same bandwidth completely. These constraints are used in the optimization algorithm. The second scheme manages the various required resources and adapts them to the beam gain and interference levels at various user locations within a single beam. We propose a fixed power adaptive modulation scheme to obtain stable communications. This two-layered scheme can satisfactorily allocate multi-beam satellite resources to contend with the increasing communication capacity and still improve the quality.

Linearity degradation due to beam coupling in a multibeam mobile satellite communications system

This paper proposes a method for analyzing repeater characteristics in a multibeam mobile satellite communications system in which beam coupling occurs. It also presents theoretical studies on the effects of adjacent-beam signals and on the relationship between traffic distribution and change in repeater linearity. It is found that the effects of signals leaked from adjacent beams, which up to now have been considered small, cannot be ignored; they depend on traffic distribution and play a role in linearity degradation and decreased maximum transmission capacity. Based on these studies, new methods are proposed for designing, configuring, and operating a system so that transmission capacity can be increased. © 1999 Scripta Technica, Electron Comm Jpn Pt 1, 82(5): 1–15, 1999

Comparative study of switching methods for the on-board processor in a mobile satellite communications system

An on-board processor makes efficient use of the channel capacities in a satellite communications system employing multibeam technology, and an on-board processor has been developed for the Engineering Test Satellite VIII (ETS-VIII), which is the experimental satellite for a multibeam mobile satellite communications system. The multicarrier time division multiple access (MC-TDMA) system used in this communications system, however, sometimes causes internal congestion in the on-board processor. This paper describes the results of computer simulation studies of the traffic capacity obtained using three baseband switching methods and also describes the results of studies of the on-board processor design for each of the methods. The computer simulation results indicate that the probability of internal congestion due to the TDMA system is very small when the simultaneous-slot switching method is used, and the design study results reveal that an on-board processor using the simultaneous-slot switching method will be compact and lightweight and will consume little power. © 1998 John Wiley & Sons, Ltd.

Soft-decision Viterbi decoding with diversity combining for multi-beam mobile satellite communication systems

Diversity combining methods for mobile satellite communication systems employing convolutional encoding and soft-decision Viterbi decoding are evaluated. Computer simulation clarifies that the pre-Viterbi-decoding maximal ratio combining method has better performance than other methods in Rician fading channels. The simulation results agree with the Pe (bit error probability) performance derived from the numerical analysis for slow fading using the approximate Pe performance of Viterbi decoding in AWGN (additive white Gaussian noise) channels and the probability density function of Rician fading. Applying this diversity method to the multi-beam mobile satellite communication systems, a satellite beam diversity reception scheme is proposed. A computer simulation result shows that the proposed scheme decreases the packet error rate of the control signals to less than 1/100 around the satellite beam boundary. >