Adaptive robust control of mobile satellite communication system with disturbance and model uncertainties

The tracking and stable control of a typical shipmounted mobile satellite communication system（MSCS） is studied.Unlike the former studies based on simplified single-axis models,a tri-axis nonlinear model including the kinematic and dynamic features of the MSCS is used as the control object.An adaptive robust controller with trajectory planning is designed to deal with large parametric uncertainties and uncertain nonlinearities of the system.A theoretic performance result is given and proved.The designed adaptive robust controller and other two traditional controllers are tested in the comparative simulations under three different situations.The simulation results show the tracking and stable validity of the proposed controller.

A NOVEL MODULATION FOR MOBILE SATELLITE COMMUNICATIONS

It is a challenging problem to design a high performance modulation for mobile satellite communications due to the limited power and bandwidth resource.The paper improves Feher patented Quadrature Phase Shift Keying(FQPSK) by redefining the waveform.The novel FQPSK,with con-stant envelope,can be used to improve the power efficiency and frequency efficiency of mobile satellite communication.The study shows that the improved FQPSK outperforms conventional FQPSK over AWGN and is immune to the non-linearity of high power amplifier.At last,the impact of flat fading and multi-path fading of channel on the BER performance of improved modulation is analyzed.

Modeling and Nonlinear Computed Torque Control of Ship-mounted Mobile Satellite Communication System

A mobile satellite communication system (MSCS) is a device installed on a moving carrier for mobile satellite communication. It can eliminate disturbance and maintain continuous satellite communication when the carrier is moving. Because of many advantages of mobile satellite communication, the MSCSs are becoming more and more popular in modern mobile communication. In this paper, a typical ship-mounted MSCS is studied. The dynamic model of the system is derived using the generalized Lagrange method both in the joint space and in the workspace. Based on the dynamic model, a nonlinear computed torque controller with trajectory planning is designed to track an aimed satellite with a satisfied transient response. Simulation results in two different situations are presented to show the tracking performance of the controller.

Cooperative Communication Protocols for Performance Improvement in Mobile Satellite Systems

A mobile satellite indoor signal is proposed to model perfor mance of cooperative communication protocols and maximal ra tio combining.Cooperative diversity can improve the reliability of satellite system and increase data speed or expand cell radi us by lessening the effects of fading.Performance is determined by measured bit error rates（BERs）in different types of coopera tive protocols and indoor systems（e.g.GSM and WCDMA net works）.The effect of performance on cooperative terminals lo cated at different distances from an indoor cellular system is al so discussed.The proposed schemes provide higher signal-tonoise ratio（SNR）-around 1.6 dB and 2.6 dB gap at BER 10-2for amplify-and-forward（AF）and decode-and-forward（DF）cooperative protocols,respectively,when the cooperative termi nal is located 10 m from the WCDMA indoor system.Coopera tive protocols improve effective power utilization and,hence,improve performance and cell coverage of the mobile satellite network.

Communication-based positioning systems:past,present and prospects

This paper reviews positioning systems in the context of communication systems. First, the basic positioning technique is described for location based ser- vice （LBS） in mobile communication systems. Then the high integrity global posi- tioning system （iGPS） is introduced in terms of aspects of what it is and how the low Earth orbit （LEO） Iridium telecommunication satellites enhance the global posi- tioning system （GPS）. Emphasis is on the Chinese Area Positioning System （CAPS） which is mainly based on commercial geostationary （GEO） communication satellites, including decommissioned GEO and inclined geosynchronous communication satel- lites. Characterized by its low cost, high flexibility, wide-area coverage and ample frequency resources, a distinctive feature of CAPS is that its navigation messages are generated on the ground, then uploaded to and forwarded by the communication satellites. Fundamental principles and key technologies applied in the construction of CAPS are presented in detail from the CAPS validation phase to its experimental system setup. A prospective view of CAPS has concluded it to be a seamless, high ac- curacy, large capacity navigation and communication system which can be achieved by expanding it world wide and enhancing it with LEO satellites and mobile base stations. Hence, this system is a potential candidate for the next generation of radio navigation after GPS.

Random access preamble design based on time pre-compensation for LTE-satellite system

Because of the integration of long term evolution （LTE） technology and mobile satellite communication systems, uplink access technology for LTE-based geo-stationary earth orbit （GEO） satellite has become a popular research topic for satellite system. In order to solve the problem of unreasonable design for physical random access channel （PRACH） signal structure and reduce the effect of time uncertainty, this paper proposes a novel random access preamble based on time pre-compensation （TPC） for LTE-Satellite （LTE-S） system. In this scheme, by applying the method of non-linear least squares, the user terminal （UT） can use and based on the transmission delay the receiving power to estimate the communication round trip delay （RTD） of the beam center and the satellite, RTD can be compensated before transmission. Therefore, the preamble length and duration can be reduced without related to the maximum of RTD. In order to verify the performance of the scheme, the MATLAB is used to build a test system. The simulation results show that the proposed preamble satisfies the requirements of LTE-S system, and the better performance than previous researches is obtained.