Mobile Satellite Communication Systems Research Articles

An authentication scheme for mobile satellite communication systems

This paper discusses the security aspects of a registration protocol in a mobile satellite communication system. We propose a new mobile user authentication and data encryption scheme for mobile satellite communication systems. The scheme can remedy a replay attack.

Study on application of CMA to land mobile LEO satellite communication systems based on a deterministic channel model

AbstractThis paper studies the application of the constant modulus algorithm (CMA) in land mobile low earth orbit (LEO) satellite communication systems. Two propagation phenomena prevail in narrow band land mobile LEO satellite channel, namely, adjacent channel interference (ACI) and frequency‐non‐selective fading. The performance of CMA for ACI cancellation and the behaviours of CMA in frequency‐non‐selective fading channels are evaluated using a digital beamforming (DBF) array antenna simulation scheme. All these evaluations are based on a simple but efficient channel model which provides a good and fast simulation method for land mobile LEO satellite channels. The restricted Jakes Doppler power spectral density (psd) function is incorporated into the model to ensure that it will be appropriate for the evaluation of a DBF antenna. Our results reveal that CMA can reject ACI and work well in frequency‐non‐selective fading channels. Copyright © 2002 John Wiley & Sons, Ltd.

Physical–statistical methods for determining state transition probabilities in mobile‐satellite channel models

AbstractSignal propagation in land mobile satellite (LMS) communication systems has for the last decade become an essential consideration, especially when high‐rate data services are involved. As far as urban or suburban built‐up areas are concerned, the extent of the influence is mainly restricted to the roadside obstacles, since the satellite is positioned at relatively high elevation angles in most practical situations. Probably, the most common model currently used for representing the LMS channel is the Lutz model, which uses two states to represent line‐of‐sight and non‐line‐of‐sight conditions. Transitions between these states are described by transition probabilities which are a function of the environment and the satellite elevation angles. Similarly, an extension to the model allows a four‐state description to be used for the states associated with a pair of satellites used in a dual‐diversity configuration. Calculation of the transition probabilities then requires knowledge of the correlation between the two channels, which in turn depends on the spatial characteristics of the local environment around the mobile.In both cases, the transition probabilities have been derived basically from measurements in the past. In the new approaches described in this paper, physical–statistical principles are applied to construct analytical formulas for the probabilities of shadowing and the correlation between states. These expressions apply particularly to systems operated in built‐up environments, and have been checked against numerical experiments and against direct measurements. In both cases excellent agreement is obtained. Copyright © 2001 John Wiley & Sons, Ltd.

A study of global multimedia mobile satellite communication system: Current status

In Japan, Next-generation LEO System (NeLS) research center was established with a support of the Ministry of Posts and Telecommunications (MPT) in the end of 1997. This research center focuses on a study for the LEO system called NeLS which would provide global multimedia mobile satellite services. The target services include up to 2 Mbps multimedia data transmission using handheld or portable terminals. The target year for operation is 2010. This paper describes the current status of technical development of the NeLS project, in terms of satellite constellation, optical inter-satellite link (ISL), satellite antenna, user link, and satellite network.

A general statistical channel model for mobile satellite systems

In order to guarantee the service quality and reliability for mobile satellite communication systems, we have to take into account outages due to obstruction of the line-of-sight path between a satellite and a mobile terminal as well as the signal fluctuation caused by interference from multipath radio waves. Thus, we need a good characterization for the satellite propagation channel. In this paper, we derive a general statistical model for mobile communication systems based on propagation scattering theory. Both the probability density function (PDF) of the received signal envelope and that of received signal power are given. This model is shown to be more general than previously known statistical models and can provide a better fit to the experimental data. This new model will play a significant role in the design of mobile satellite communication systems.

COMETS experiments for advanced mobile satellite communications and advanced satellite broadcasting

The Communications and Broadcasting Engineering Test Satellite (COMETS) was developed to evaluate Ka-band (31/21GHz) and millimetre-wave (47/44 GHz) advanced mobile satellite communications systems, 21GHz advanced satellite broadcasting systems, and S-band and Ka-band inter-orbit satellite communications systems. COMETS was launched because it was to become the new ‘bridge’ toward advanced satellite communications technologies in the next century, but the launch on 21 February 1998 regretfully failed due to premature shut down of the second stage engine of the H-II launch rocket. After this accident, the initial low elliptic orbit of COMETS was improved by the apogee engine to a larger elliptic orbit with an apogee altitude of 17711km, a perigee altitude of 473 km, an inclination of 30.1°, and an orbital period of 319 min. Original and modified COMETS experimental plans, countermeasures in earth stations for the orbiting satellite, as well as an overview of the COMETS satellite and ground terminals are presented. Copyright © 2000 John Wiley & Sons, Ltd.

Measurement and modelling of wideband propagation at L- and S-bands applicable to the LMS channel

Results of a wideband propagation measurement campaign applicable to mobile satellite communication systems at L- and S-band are presented. First-order statistics, including RMS delay spreads and cumulative probability density functions are presented for elevation angles from 15/spl deg/ to 80/spl deg/, and for a wide range of propagation surroundings, including urban, wooded and open environments. Typical RMS delay spread values are found to be in the region of 40 ns. In open conditions, the statistical analysis of the line-of-sight-path signal shows a form close to a Rician distribution, as expected, but, under shadowed conditions, the distribution is closer to Rayleigh. Amplitude and phase measurements are made during the campaign and allow second-order statistics to be evaluated from the data, examples of which are given for the urban/suburban and open environments. The second-order statistics, in the form of level crossing rates, should provide a more accurate characterisation of the channel.

A compact switched‐beam array antenna for mobile satellite communications

This paper presents the design and development of a compact switched-beam array antenna for operation with the Australian mobile satellite communications system. MobilesatTM. The antenna is formed by eight aperture-coupled microstrip patch elements that are positioned on the side of a truncated cone. Two elements, facing the satellite, are activated using an eight-way two-ports-on radial switch. The output ports of the radial switch incorporate 1-bit phase shifters. A total of 24 beams are produced using this beam-forming system. In order to reduce the manufacturing cost, inexpensive substrates and low-cost UHF p-i-n diodes are employed. Further reduction in cost is achieved by eliminating coaxial connectors between the beam-forming network and the antenna elements. Experimental results are presented for the individual antenna elements, the beam-forming network, and the entire switched-beam array. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 21: 186–191, 1999.

A compact switched-beam array antenna for mobile satellite communications

This paper presents the design and development of a compact switched-beam array antenna for operation with the Australian mobile satellite communications system. Mobilesat(TM). The antenna is formed by eight aperture-coupled microstrip patch elements that are positioned on the side of a truncated comb Two elements, facing the satellite, are activated using an eight-way two-ports-on radial switch. The output ports of the radial switch incorporate 1-bit phase shifters A total of 24 beams are produced using this beam-forming system. lit order to reduce the manufacturing cost, inexpensive substrates and low-cost UHF p-i-n diodes are employed Further reduction in cast is achieved by eliminating coaxial connectors between the beam-forming network and the antenna elements. Experimental results are presented for the individual antenna elements, the beam-forming network, and the entire switched-beam array. (C) 1999 John Wiley & Sons, Inc.

Satellite Based Mobile Communication—A perspective

It is expected that mobile satellite communication system will bring a big change in the overall world communication scenario. In this paper efforts are made to explain the salient technical features of such systems being deployed/proposed by various international organisations and industries.

Distributed source coding for satellite communications

Inspired by mobile satellite communications systems, we consider a source coding system which consists of multiple sources, multiple encoders, and multiple decoders. Each encoder has access to a certain subset of the sources, each decoder has access to certain subset of the encoders, and each decoder reconstructs a certain subset of the sources almost perfectly. The connectivity between the sources and the encoders, the connectivity between the encoders and the decoders, and the reconstruction requirements for the decoders are all arbitrary. Our goal is to characterize the admissible coding rate region. Despite the generality of the problem, we have developed an approach which enables us to study all cases on the same footing. We obtain inner and outer bounds of the admissible coding rate region in terms of /spl Gamma//sub N/* and /spl Gamma/~/sub N/*, respectively, which are fundamental regions in the entropy space defined by Yeung (1991). So far, there has not been a full characterization of /spl Gamma//sub N/*, so these bounds cannot be evaluated explicitly except for some special cases. Nevertheless, we obtain an alternative outer bound which can be evaluated explicitly. We show that this bound is tight for all the special cases for which the admissible coding rate region is known. The model we study in this paper is more general than all previously reported models on multilevel diversity coding, and the tools we use are new in multiuser information theory.

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

Research and development of On-Board Processor for advanced mobile satellite communications

This paper describes the research and development of an On-Board Processor (OBP) for a mobile satellite communications system using a geostationaly satellite. The system, which based on Multi-Carrier Time Division Multiple Access, can realize high performance and facilitate the use of miniature hand-held mobile Earth terminals. Our research and development results indicate as follows. 1. 1) The simultaneous-slot switching method will be the most suitable for an on-board base-band switching with consideration of traffic capacity, time delay, and hardware scale. 2. 2) The OBP performs channel exchange with regeneration that contributes to a reduction in the size of mobile terminals because of the coding gain. 3. 3) Many kinds of Application Specific Integrated Circuits are designed to realize large channel capacity and reduce the size and power consumption of the OBP. These OBP design can increase the channel capacity, which is equivalent to in 5.6kbps voice channel, up to over 500 channels within 5MHz frequency band Some results are applied to the OBP being developed for the Japanese Engineering Test Satellite VII (ETS-VB).

Efficient adaptive coding scheme in mobile satellite communication channel

The introduction of global mobile personal communications by satellite (GMPCS) systems makes it possible to provide high-quality services, especially by using low earth orbit (LEO) or medium earth orbit (MEO) satellites. In mobile satellite communication systems such as GMPCS systems, error correcting coding schemes are needed to achieve a desirable quality of service, and the coding scheme should be efficient in terms of the frequency spectrum as well as the power. Efficient coding schemes which employ trellis decoding methods with Reed–Solomon (RS) codes are proposed. These schemes can be used adaptively in time-varying fading conditions of mobile satellite communication channels. Simulations have been performed using a mobile satellite channel model as well as using an additive white Gaussian noise (AWGN) channel model. The results showed that the proposed schemes can achieve a better performance with less decoder complexity than a rate 1/2 constraint length 7 convolutional code in any fading environment.

Physical–statistical prediction of performance for land mobile satellite communication systems

A performance analysis of land mobile satellite systems is presented. A physical–statistical model is applied to infer narrowband channel parameters, such as fade distribution, level-crossing rate or bit error ratio. The physical–statistical approach combines a ray-tracing tool with the statistical distribution of the parameters describing the environment. Simulation results are successfully compared with measurements at the L-band. The model is then used to predict the performance of a typical LMS system, with a new point of view, which differentiates temporal availability and spatial coverage. The physical nature of the method highlights the role of relevant parameters.

Propagation model for building blockage in satellite mobile communication systems

A propagation model for building blockage in satellite mobile communication systems is developed. This model characterizes the signal transmitted from a low-Earth orbiting (LEO) satellite when there is an obstruction in the path of the signal. The obstruction is assumed to be a man-made structure. The analysis is performed using the uniform theory of diffraction (UTD). Using this method, both single and double diffractions from the structure edges were included. Direct and reflected rays from the ground and building were also included, whenever the satellite signal was not completely obstructed. The satellite is assumed to be moving along a circular orbit while the receiver is stationary. The normalized signal level (in decibels) and the signal attenuation rate (in decibels per second) are computed. Such information is considered very useful in developing the mobile system's hand-off algorithm.

A high capacity third‐generation mobile satellite system design

AbstractThis paper describes a CDM/CDMA based approach for a 3‐rd generation multi‐beam satellite mobile and personal communications system using Highly Elliptical Orbit (HEO) satellites. The forward link uses a synchronous CDM intra‐beam/asynchronous CDM inter‐beam approach, while the return link uses a quasi‐synchronous CDMA intra‐beam/asynchronous CDMA inter‐beam approach. Using probabilistic analysis, these approaches are shown to provide higher forward and return link capacities than equivalently synchronized FDM/FDMA approaches. Forward link transmissions are modulated using QPSK. Return link transmissions are modulated using either ϕ/4‐QPSK or precompensated frequency modulation (PFM4). PFM4 is intended for use with a saturated amplifier in low‐cost/power‐efficient, e.g. hand‐held, terminals, and can be demodulated using a ϕ/4‐QPSK receiver. All forward and return link transmissions are coded using a rate 1/2, constraint length 9, convolutional code. The paper summarizes several key tradeoffs and the resulting system design.

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

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

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.

DS-CDMA satellite diversity reception for personal satellite communication: satellite-to-mobile link performance analysis

The satellite-to-mobile link of a mobile personal satellite communication system employing power-controlled direct-sequence code-division multiple access (DS-CDMA) and exploiting satellite diversity is analyzed and its performance compared with a more traditional communication system utilizing single-satellite reception. The semianalytical model developed has been thoroughly validated by means of extensive Monte Carlo computer simulations. System capacity and performance have been numerically evaluated in the presence of a realistic operating scenario, including antenna radiation pattern, imperfect power control, shadowing, and cross-polarization effects. It is shown how the capacity gain provided by diversity reception considerably shrinks in the presence of increasing traffic or in the case of mild shadowing conditions. Moreover, the quantitative results tend to indicate that to combat system capacity reduction due to the intrasystem interference, no more than two satellites sharing the same frequency slot must be active over the same region.