Land Mobile Satellite Communication System Research Articles

Physical Layer Security in Interference Limited Land Mobile Satellite Communication Systems: Safeguarding Data Transmission

This paper focuses on evaluating the secrecy performance of a downlink land mobile satellite (LMS) system. The system faces the challenge of providing secure communication between a satellite and a legitimate user while an eavesdropper is present on the ground. Additionally, co-channel interference signals at the user's destination are considered. To address these issues, the study proposes a novel approach that utilizes Shadowed-Rician fading channels for satellite links and Nakagami-m fading for interfering terrestrial links. The main objective is to enhance the physical layer security of Interference-Limited Land Mobile Satellite Communication Systems. The approach incorporates advanced signal processing, beamforming, and artificial noise techniques to effectively manage interference. Encryption, authentication mechanisms, and intelligent power control strategies are implemented to protect transmitted data and optimize signal strength while reducing the risk of interception by potential eavesdroppers. Through comprehensive simulations, the proposed approach is thoroughly evaluated, demonstrating its effectiveness in achieving improved secrecy performance and increased resilience against security threats. The findings highlight the potential for its application in secure satellite communication systems operating in interference-constrained environments.

Secrecy Performance of Land Mobile Satellite Systems With Imperfect Channel Estimation and Multiple Eavesdroppers

The inherent broadcast nature has exposed the land mobile satellite (LMS) communication systems to severe security threats in both the civil and military applications. This paper investigates the secrecy performance of a Shadowed-Rician fading multi-antenna LMS communication system with imperfect channel estimation, which consists of a satellite, a legitimate receiver and a cluster of unauthorized eavesdroppers who want to overhear the confidential message. Specifically, the analytical expressions for the probability of non-zero secrecy capacity are derived in terms of the Meijer-G functions, which provide an efficient means to evaluate the secrecy performance of the system. Then, both the exact and asymptotic secrecy outage probability expressions of the considered system are obtained. Furthermore, based on the simple asymptotic secrecy outage probability, we can reveal two key performance metrics, namely, the secrecy diversity order and secrecy array gain. Finally, simulation results are carried out to validate the theoretical results and show the superiority of employing multiple antennae in enhancing the secrecy performance for LMS communication systems. Our findings suggest that the secrecy diversity order only depends on the number of antennas at the legitimate receiver, and is independent of the imperfect channel estimation and the shadowing severities of both the main and eavesdropper channels.

An iALM-ICA-Based Antijamming DS-CDMA Receiver for LMS Systems

We consider a land mobile satellite communication system using spread spectrum techniques where the uplink is exposed to multitone jamming attacks, and the downlink is corrupted by multipath fading channels. We propose an antijamming receiver, which exploits inherent low-dimensionality of the received signal model, by formulating a robust principal component analysis-based recovery problem. Simulation results verify that the proposed receiver outperforms the conventional receiver for a reasonable rank of the jamming signal.

OSTBC Transmission in Shadowed-Rician Land Mobile Satellite Links

In this paper, we study the transmission of orthogonal space–time block codes (OSTBCs) over a shadowed Rician (SR) land mobile satellite (LMS) link. Specifically, we derive the symbol error rate (SER), diversity order, and the average capacity of the OSTBC-transmission-based scheme over the SR fading LMS communication systems. First, we consider the independent and identically distributed (i.i.d.) SR fading channels and derive the expressions of moment-generating function (mgf) in terms of the Meijer-G function. By substituting the Meijer-G function in terms of hypergeometric function and then by considering the asymptotic approximation of hypergeometric function, the analytical diversity order of the scheme is obtained. The ergodic capacity of the scheme is derived by using the mgf-based approach. The effect of elevation angles over the SER performance of the scheme is analyzed, and it is observed that the performance of the system is improved with increasing values of elevation angles. Next, we consider the OSTBC transmission over correlated SR fading channels and derive the expressions of mgf, SER, diversity order, and average capacity of the considered setup. In particular, it is demonstrated in this paper that, by employing an additional transmit antenna at the satellite along with Alamouti code, the error rate of the LMS communication system can be significantly improved. It is also shown that the correlation has no impact on the diversity order of the system, but it adversely affects the capacity of the system.

Adaptive Long-Range Prediction of Three-State LMS Channel Model

In order to provide the accurate real-time knowledge of future channel state information for the adaptive transmission of narrowband land mobile satellite (LMS) communication systems, an adaptive long-range prediction (ALRP) method, suitable for a three-state LMS channel model at S-band, is proposed. The very slow shadowing conditions' variations of satellite propagation channel can be described as a three-state Gilbert---Elliot channel model based on Markov chain. The channel state of future long-range is predicted based on weighting prediction while the parameters of linear auto-regression model are updated using an iterative adaptive tracking algorithm. The future channel fading series are predicted by the latest observations within current channel state. Simulation results show that the proposed method can be used to predict the future long-range channel state and fading series of three-state Gilbert---Elliot channel model accurately; and it is observed from the mean square error results that the prediction performance of the ALRP method is much more accurate than that of long-range prediction method. Moreover, the method has advantage of real-time and low-complexity which will make the adaptive transmission techniques feasible for LMS channel models.

육상 이동 위성 시스템의 통신 성능 향상을 위한 MIMO 원형 편파 급전 네트워크

본 논문은 육상 이동 위성(Land Mobile Satellite: LMS) 시스템의 통신 성능 향상을 위해 기존의 <TEX>$2{\times}2$</TEX> MIMO 채널에서 <TEX>$4{\times}4$</TEX> 채널로 확장할 수 있는 MIMO 원형 편파 급전 네트워크를 제안한다. 기존의 추가적인 통신 채널 확보를 위해서는 위성국에서 안테나 설치 공간상의 제약이 있기 때문에 이격 거리가 충분한 추가 위성국을 필요로 한다. 이로 인한 비용 및 MIMO 통신 채널의 한계 문제를 극복하기 위하여, 동일한 원형 편파 간에 이격 거리가 없이도 높은 격리성을 확보할 수 있는 MIMO 원형 편파 급전 네트워크를 제안하였다. 제안하는 급전 네트워크의 포트간 격리성과 각 포트의 매칭 상태를 수식적으로 증명하였고, <TEX>$4{\times}4$</TEX> MIMO 채널의 통신 성능 향상을 채널 모델 측면에서 제시 및 확인하였다. MIMO 원형 편파 급전 네트워크를 원형 편파 패치 안테나 구조로 실제 제작하고 측정하여 7~10 dB의 다이버시티 이득을 얻었고, 약 1.8배로 채널 용량이 향상되었음을 확인하였다. In this paper, we propose the MIMO circular polarization feed network to enhance the communication performances from the previous <TEX>$2{\times}2$</TEX> MIMO channel to <TEX>$4{\times}4$</TEX> channel for Land Mobile Satellite communication system. The only possibility to extend the communication channel is to use the additional satellite because of the limitation of satellite spaces to install additional antennas. For overcoming this problems, we propose the MIMO circular polarization feed network to secure the isolation characteristics without the distant antenna space. The port isolation characteristics and each port impedance matching conditions are numerically verified and we suggest the <TEX>$4{\times}4$</TEX> MIMO channel model of the proposed system and the performances are verified. The fabricated circular polarization patch antennas with the proposed feed network are measured in the reverberation chamber and 7~10 dB of diversity gain and 80 % increasement of channel capacity are obtained.

Dual Hop MIMO OSTBC for LMS Communication

For a multiple antenna land mobile satellite (LMS) communication system with a terrestrial relay node, the system performance when channel state information (CSI) is not available at the source and the relay is analyzed. The system employs orthogonal space time block code (OSTBC) encoding with fixed gain amplify and forward (AF) relaying. The moment generating function (MGF) and first and second moments of the signal-to-noise ratio (SNR) at the destination are derived in exact closed form. The average symbol error rate (SER) and the amount of fading (AoF) of the system are also derived.

Performance Analysis of Land Mobile Satellite Communication Systems with Equal-Gain Combining over Shadowed-Rice Fading Channels

An accurate model for performance analysis of land mobile satellite (LMS) channels is the Shadowed-Rice (SR) fading model. Recently, an approximate SR model has been proposed by the author for LMS channels. Compared with the existing models, the proposed model is analytically tractable and makes it possible to approximate very accurately the probability density function (PDF) of the SR random variable (RV) by a finite weighted sum of Rice PDFs. In this paper and based on the proposed model, the statistics of the sum of independent SR RVs is studied. While this problem is well understood for common fading models such as the Rayleigh, Rice, and Nakagami, a minor attention has been devoted to the SR case. In this paper and by using the well-known Beaulieu series approach, the PDF and the Cumulative distribution function (CDF) of the sum of independent SR RVs are derived in the form of infinite convergent series. In this regard, analytical, closed-form expressions are derived for the coefficients of the Beaulieu series. To give an application of the presented results, the performance of LMS communication system employing equal-gain combining (EGC) diversity techniques over SR fading channel is investigated and novel closed-form expression is derived for the outage probability of the system.

Web traffic capacity of multi-beam GEO and MEO mobile satellite systems

An investigation into the downlink web traffic capacity of W-CDMA land mobile satellite communication systems for Geostationary (GEO) and Medium Earth Orbit (MEO) constellations is presented. It is shown that the effect of power control errors on the web traffic capacity severely degrades the performance of mobile satellite systems. It is also shown that the use of the proposed macrodiversity system is to mitigate the effect of power control errors, and consequently increases the web traffic capacity of multi-beam GEO and MEO mobile satellite systems.

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 &amp; Sons, Ltd.

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.

Signal fading in land-mobile satellite communication systems: Statistical characteristics of data measured in Japan using ETS-VI

The space–earth links in land-mobile satellite communications are frequently cut off as a result of the shadowing and blockage, due to roadside trees, buildings, utility poles, and other artificial obstacles. Knowledge about the fade statistics is therefore important in designing cost-effective land-mobile satellite communication systems. Using a 15.5 dBi-gain satellite-tracking antenna, an S-band (2.1 GHz) unmodulated continuous-wave signal transmitted from the elliptically orbiting ETS-VI satellite was measured, while the vehicle the antenna was mounted on was driven around a city in Okinawa. The investigation reports on fade statistics and fade and nonfade-duration (interfade-duration) statistics for elevation angles ranging from 57.9° to 66.5° and for several thresholds of fade state (fade margins from 3 to 15 dB).

Dual-Space Diversity over Land Mobile Satellite Channels Operating in the L and K Frequency Bands

Land mobile satellite communication systems at Ka/K band (30/20 GHz) are attracting more and more attention to researchers because of its frequency band availability and the possibility of using small earth stations and satellite antennas for the systems. However, the Ka/K-band communications also give significant challenges in the system design due to severe channel impairments expected from the satellite links. In this paper, K-band channel characteristics are studied and compared with those at L band. The channel is modeled as Rayleigh multipath fading with the line-of-sight (LOS) component following a lognormal distribution. The first and second-order statistics of the fading channel are studied. Dual-space diversity reception is investigated to combat the flat channel fading. The bit error rate performance of coherent binary phase shift keying (BPSK) with ideal bit and carrier phase synchronization over the fading channel at K band is evaluated theoretically and verified by computer simulations in the case with and without diversity reception.

Fade statistics measured by ETS-V in Japan for L-band land-mobile satellite communication systems

Fade statistics were measured along 4095 km of expressways using a 12 dBi gain antenna with an automatic tracking system. The results show that the line-of-sight statistics, which were available for more than 90% of total distance, can be described by a Rician distribution with Rician factors of 15 to 25 dB.

Land mobile satellite communication system using the geostationary platform

If the geostationary platform (GPF) is available in the first decade of the 21st century, the demand on a voice communication base is expected to be about 800,000 Land Mobile Satellite Service (LMSS) terminals. To improve the frequency use of an LMSS over Japan, it is important to reuse the frequencies allocated to the Tokyo metropolitan area in the Osaka-Kobe-Kyoto region. An onboard multibeam antenna with beam intervals of 0.468 deg (L band 30-m class) for each of the 11 beams covering the main Japanese islands, cluster power feeding, and dual polarization can enable the reuse of frequencies at one-beam intervals. A deployable antenna is under development that is lightweight and has a high storage efficiency for launching. This will form the basis for an antenna with an aperture diameter of 30 m. Such a large antenna will be a key factor in reducing ground terminal size. This paper estimates the weight and power requirements of the mission payloads onboard the GPF, which include an LMSS, a millimeter wave personal satellite communication system, and a high-definition television/regional television satellite broadcasting service system. The total weight of this GPF would be approximately 4-5 tons.

Direct-sequence spread spectrum in a shadowed Rician fading and land-mobile satellite channel

The performance of a direct-sequence spread-spectrum land-mobile satellite transmission system, using binary phase-shift keying (BPSK) modulation, is analysed. The satellite channel is modeled as having Rician fading characteristics. The bit-error probability is evaluated, considering both the envelope and the phase variation. Assuming a Gaussian approximation for the interference, numerical results are obtained for both spread-spectrum and narrowband land-mobile satellite communication systems with BPSK modulation. A comparison of the two systems is made for light, average, and heavy shadowing. >

Fully digital M-ary psk and M-ary qam demodulators for land mobile satellite communications

A fully digital implementations of digital modems is the preferred option of system designers because high performance can be achieved at reasonable cost. The paper explains the beneficial features inherent in fully digital demodulator implementations. Other features which are required for land mobile satellite communication systems are also discussed. Recently reported techniques for the synchronisation and detection of M-ary PSK and M-ary QAM modulation schemes are reviewed with emphasis placed on those which are well suited to digital implementation.

Digital transmission through a land mobile satellite channel

An analytical derivation of the probability of bit error noncoherent frequency-shift keying (FSK) and coherent phase-shift keying (PSK) signals transmitted through a land-mobile satellite channel is described. The channel characteristics used in the analysis are based on a recently developed model which includes the combined effects of fading and shadowing. Analytical expressions for the probability of bit error of FSK and coherent phase-shift keying (CPSK) signals are obtained. The results show that large amounts of signal-to-noise ratio (SNR) are required to compensate for the combined effect of fading and shadowing. An analytical expression for the irreducible probability of bit error of a CPSK signal due to phase variations caused by fading and shadowing is derived. The results described should be useful in the design of land mobile satellite communication systems. >