Personal Satellite Communications Research Articles

A Survey on Robust Modulation Requirements for the Next Generation Personal Satellite Communications

The unrelenting technological advancement in the generation of wireless networks in recent years has awakened the motion concerning the inclusion of satellites in personal communications. Leveraging their ability to provide wide coverage, uniform services, wide bandwidth, and so forth, Satellite systems will be expected to co-exist with the current state-of-the-art infrastructure of terrestrial networks. Herein, we present a comparative study on the representative digital modulation techniques for use in personal satellite communications. We discuss the advantages and limitations of different modulation techniques, such as phase shift keying, continuous phase modulation, amplitude phase shift keying, and quadrature amplitude modulation. We also perform evaluations based on spectral efficiency, power efficiency, modulation error ratio, error vector magnitude, and peak-to-average power ratio in the presence of high power amplifier nonlinearities and Doppler effects. Comparisons in the form of tables, illustrations, and curves are also presented. In correspondence to the comparisons made basing on the aforementioned metrics, we conclude that continuous phase modulation is the best candidate modulation scheme for personal satellite communications since it outperforms other schemes by compromising the trade-off between power efficiency, bandwidth efficiency, and immunity to errors. We further present open issues that would reinforce personal satellite communications in terms of reliability, throughput and latency, other than power and spectral efficiency, if combined with appropriate modulation schemes.

Development of a modern global information infrastructure based on a personal satellite communication system

The information industry is the main branch of the modern economy. The processes of informatization lead to qualitative changes in society itself in the direction of acquiring sustainable features of the modern information society, the technological basis of which is the global information infrastructure (GII). GII provides free access to information resources to every inhabitant of the planet and provides a set of communication services that provide an open set of applications, covers all types of information and provides the opportunity to receive it anywhere, anytime, at an affordable price and at an affordable price quality. The creation and operation of modern satellite communication systems contributes to the creation of a global information infrastructure. Satellite communications, which is a promising component of modern cyberspace infrastructure, is qualitatively changing the entire telecommunications industry and affecting the usual way of life. Personal satellite communication systems have significant advantages over mobile communication systems. Today, the use of new spacecraft with improved characteristics is expected, which will represent almost the entire range of satellite services. According to documents submitted to the US Federal Communications Commission, satellites in space will «communicate» with each other at a frequency of more than 10 thousand GHz using a laser beam. Ground stations and user terminals will be communicated on 12 GHz radio bands. The promised data rate is 1 Gbps for each consumer. Regarding potential Starlink applications, SpaceX’s management points to the risky nature of the low-bandwidth broadband satellite business and adds that SpaceX plans to use its Starlink satellites not only to provide broadband Internet connectivity in remote areas of the world, but also to connect on other planets.

Personal satellite communication: technologies and challenges

Communication regulatory bodies in many parts of the world have recently granted satellite operators the right to extend their networks by adding ground segments. This has opened the door, for the first time, to truly ubiquitous satellite coverage, thus revolutionizing the use of satellites in personal communications. In this article, we review personal satellite communication systems. Background on the evolution of satellite communications is given along with the basics of satellite systems. This is followed by a comprehensive discussion of the current challenges facing the future of personal satellite communication systems and some of the proposed solutions.

Wearable Circularly Polarized Antenna for Personal Satellite Communication and Navigation

Integrating antennas into fabrics is a potential way for facilitating many applications, such as health monitoring of patients, fire-fighting, rescue work, and space and military personal communications. This paper studies possibilities to construct a flexible, lightweight and mechanically robust textile antenna for dual-band satellite use: Iridium and GPS. Different textile materials were characterized and the most promising materials were used to design, construct, and test a rectangular patch antenna. The gain and axial ratio for both bands is compliant with specifications and relatively stable under most bending conditions. The developed antenna solution allows integration into clothing.

Application of unified methodical approach to online planning of target operation of satellite monitoring and communication systems

A unified methodical approach to online planning of target operation of satellite monitoring and communication systems is considered. Based on the general principles of formal representation of optimization problems of online planning for such systems and the methods and algorithms proposed for their solution, the generalized mathematical statement of the problem of online planning is presented, and the main stages of application of this methodical approach to its solution are unified; the approach is of practical interest both for monitoring and communication systems. The application of the methodical approach is demonstrated using the examples of planning the controlled process of target operation of multisatellite systems: for monitoring of fire-risky region by low-orbit satellites of the project China-Brazil Earth Remote Satellite (CBERS) and for speech transmission via mobile channels in low-orbit global systems of personal satellite communication of the projects “Koskon” and “Iridium”.

Interference Mitigation in Satellite Personal Communication Networks Using Adaptive Antenna Arrays and Filtering Technique

We address the problem of interference as related to Satellite Personal Communication Networks (S-PCNs). Basic low Earth orbit (LEO) constellation is considered. The paper uses combined adaptive antenna arrays and adaptive filtering technique. This hybrid linear adaptive technique provides improved performance eliminating interference, particularly uncorrelated signals residing in the antenna sidelobes.

Iteration-based identification of faulty links in LEO/MEO satellite communication networks

Satellite systems are going to be an important part of the future personal communication infrastructure. The first-generation candidates for satellite personal communication networks (S-PCN) will rely on low earth orbiting (LEO) and medium earth orbiting (MEO) constellations. For LEO satellite systems employing intersatellite links (ISLs), we present a iteration-based algorithm to identify faulty links, which applies to a satellite network assuming a connection-oriented network structure, e.g., ATM or ATM-type switches on-board satellites. In the algorithm a management satellite can autonomously and real-time identify a ranked list of the most probable failed network links through building discrete-time dynamic virtual topology graph (DT-DVTG), then testing can be used to quickly pinpoint the actual faulty links. The performance of the algorithm is evaluated through simulations.

Adaptive coding and modulation scheme for satellite-UMTS TDD systems based on a photogrammetric channel estimation method

The conventional wireless communication systems are designed to overcome the worst-case channel, using the huge amount of redundant bits to assure communications performance and quality of services. Those systems cannot achieve the optimum spectrum and power efficiency. This paper presents an adaptive coding and modulation scheme used in the user terminals of the third-generation satellite communication system. A three-state photogrammetric channel estimation method is introduced for tracing the variations of large-scale environments. The mobile user terminal dynamically switches the suitable coding and modulation schemes according to the result of photogrammetric channel estimator in order to maximize the power efficiency and data throughput. The real measurement data were used to validate our proposed method. The results show that the proposed method not only reduces the system complexity, but also mitigates the power control requirements and increases the data throughput for the land mobile satellite personal communication systems. Copyright © 2006 John Wiley & Sons, Ltd.

Investigations of polarization purity and specific absorption rate for two dual-band antennas for satellite-mobile handsets

A study of the effects of human proximity on the polarization purity of two types of circularly-polarized handset antennas for personal satellite communications was investigated using the hybrid method of moments (MoM)/finite-difference time-domain technique. Associated with this, assessments of specific absorption rate in the head were made. The method gave stable results, in accordance with physical expectations; good agreement with the pure Method of Moments was shown in simplified cases omitting the head. The quadrifilar spiral antenna (QSA) was shown to be a propitious design for personal satellite communications.

Two-level, multistate Markov model for satellite propagation channels

A new model to provide more states of the Markov model while limiting the size of the Markov transition matrix is proposed to save processing time and reduce memory requirements in predicting the fading statistics and error probability of land mobile satellite systems (LMSS) and satellite personal communication services (S-PCS). Propagation fading is treated as slow fading (or shadowing) and fast fading (or multipath fading). Both of these levels can be separated into several propagation states. Two Markov state transition matrices are introduced to simulate the variation in the strength of the received signal caused by shadowing and multipath fading. Fading statistics and error probability in typical mobile user environments are accurately predicted. The advantage of this new model over the traditional single Markov state transition model is that it can generate more accurate simulation results and help to predict performance. This simple and efficient model extends the application of the Markov process method to propagation channel modelling for LMSS and S-PCS.

Maltese-cross coaxial balun-fed antenna for GPS and DCS1800 mobile communication

A novel antenna in the shape of a Maltese cross has been developed for GPS satellite and DCS1800 personal communication system application. This antenna exhibits good circular polarization (axial ratio <2 dB) and impedance performance over a bandwidth wide enough to cover the frequency band for GPS and DCS1800 reception. The addition of an adjustable clamp and tapering of the shape of the radiating elements improved the overall design. The gain of this antenna has been sufficiently high to compensate for the power loss due to polarization mismatch for the reception of a linearly polarized GSM/DCS1800 signal. A modular design and integration approach is presented to obtain the circular polarization required for GPS application.

Analyzing GPS signals to investigate path diversity effects of non‐geostationary orbit satellite communication systems

AbstractThe concept behind path diversity is that a user who can access several satellites simultaneously will be able to communicate more effectively than a user who could only access one. The success of this method depends on the environment, the satellite constellation, and diversity combining technology. This paper explores the path diversity effects of non‐geostationary orbit (NGO) satellite personal communication services, for different degrees of user mobility, under various scenarios, using the constellation of the global positioning system (GPS). Measurements are taken near downtown Taipei. Three types of mobilities (fixed‐point, pedestrian, and vehicular) are examined, and the switch diversity and maximum ratio combining method are applied to determine the path diversity gain and calculate bit error probability. The error probability performance of applying diversity schemes in coherent binary phase shift keying (BPSK) and non‐coherent differential phase shift keying (DPSK) modulations over Rician fading channels are also analysed and evaluated by using the characteristic function method. The results show that fading can be significantly reduced and diversity greatly increased. A significant diversity gain and improvement in bit error rate (BER) can be expected in all cases by simply applying switch diversity scheme. Besides, for the maximum ratio combining method, the results imply that summing two satellite signals suffices to increase diversity and improve the bit error rate performance. Copyright © 2002 John Wiley &amp; Sons, Ltd.

Dual-frequency dual-polarized slot-coupled compact microstrip antenna for communication systems

A new design of a dual-frequency dual-polarized square microstrip antenna fed along the diagonal, embedded with a square slot having three extended stubs for frequency tuning, is introduced. The proposed antenna was fabricated using a standard photolithographic method and the antenna was tested using the HP 8510C Vector Network Analyser. The antenna is capable of generating dual resonant frequencies with mutually perpendicular polarizations and broad radiation pattern characteristics. Such dual-frequency designs find wide applications in personal mobile handsets combining GSM and CDS 1800 modes, and applications in which different frequencies are used for emission and reception such as personal satellite communications and cellular network systems.

Doppler spread characteristics of satellite personal communication channels

AbstractThe paper presents a general description of Doppler characteristics of the complex LEO satellite (low earth orbit) to ground terminal channel of S‐PCS (satellite personal communication system). The difference between the terrestrial and satellite PCS radio channels is pointed out. It is shown that in the latter there is a nonzero (average) Doppler shift and a spread being independent of the radial speed of the satellite; this is in contrast to terrestrial situations in which the average Doppler shift is zero. It is also shown that in contrast to terrestrial situations there is no unique relation between the incoming ray angle of arrival and Doppler shift. Doppler spectrum is computed for a realistic distribution of scatterers close to the ground terminal; the spectral density is proportional to 1/ν3 if the ground terminal is stationary, where ν denotes the Doppler frequency. Copyright © 2001 John Wiley &amp; Sons, Ltd.

Investigations of polarisation purity and SAR for personal satellite communications antennas using a hybrid computational method

The use of the hybrid method of moments/finite difference time domain technique can be effective for solution of electromagnetic problems which are intractable for a single numerical method. Using this method, a study of the effects of human proximity on the polarisation purity of different types of circularly-polarised handset antennas for personal satellite communications was undertaken. Associated with this, assessments of the specific absorption rate in the head were made. The method gave stable results, in accordance with physical expectations; good agreement with the pure method of moments was shown in simplified cases omitting the head.

Payload nonlinearity impact on the Globalstar forward link multiplex .II. System analysis

For pt. I see ibid., vol.48, no.3, p.960-76 (1999). This paper extends at system level the analysis of on-board nonlinearity effects covered by a companion paper. A satellite personal communication network (S-PCN) like Globalstar utilizing bent-pipe transponders and active phased-array antennas in conjunction with code-division multiple access (CDMA) is considered. The present analysis incorporates the effects of payload nonlinearity, variable-rate vocoders, and multibeam interference. It is shown that nonlinearity effects on the system capacity are generally negligible except for extremely loaded beam conditions which are rare events.

Payload nonlinearity impact on the Globalstar forward link multiplex. I. Physical layer analysis

Forthcoming satellite personal communication networks (S-PCNs) like Globalstar are going to use bent-pipe transponders and an active phased-array antenna in conjunction with code-division multiple access (CDMA). Efficient payload operations require operating the on-board power amplifiers (PAs) close to their saturated power whereby distortion effects cannot be neglected. This paper analyzes the impact of solid-state amplifiers on the Globalstar forward link multiplex when a single PA per beam is used and for the more practical case of an active phased-array satellite antenna. It is shown that the conventional noise power ratio (NPR) intermodulation figure fails to accurately predict the end-to-end system performance. Multibeam active-phased array is shown to provide superior performance compared to a system employing a single amplifier per antenna beam.

Satellite systems for personal communication networks

The paper addresses some issues related to Satellite Personal Communication Networks (S-PCNs). The role of satellite communications in that scenario is discussed, and some characteristics of S-PCNs are identified. In addition, the problem of the integration of S-PCNs with the Universal Mobile Telecommunication System (UMTS) is considered. In this respect an original methodology for accomplishing such integration is proposed; such methodology aims at avoiding complex protocol conversions at the interfaces between the terrestrial and the satellite segment. The paper is partly based upon the work performed by the authors in the framework of the European Community INSURED Project “INtegrated Satellite UMTS Real Environment Demonstrator”.

Propagation fade prediction for satellite personal communication services

A photogrammetric fading prediction method for mobile satellite scenarios is introduced. Using this photogrammetric satellite services prediction (PSSP) method, the first- and second-order statistics of satellite-earth propagation fading properties can be easily obtained. Also, the fading properties as a function of elevation angle can be effectively predicted without any new radio frequency measurements. Simulated fading properties were compared with measured data in selected environments of Pasadena, California and Ottawa, Canada. The close agreement between simulated and measured results strengthens the promise of using the PSSP method to predict fading properties in various mobile user environments.

Smart antenna system and its application in low-earth-orbit satellite communication systems

Space-division-multiple-access is one of the solutions for increasing the system capacity as well as improving the system performance in wireless communications. Experimental studies have been reported; using a smart antenna system to exploit spatial diversity in low-Earth-orbit (LEO) satellite personal communication services (S-PCS). The paper presents direction-of-arrival (DOA) estimation of satellite signals, variation of spatial signature and DOA with frequencies, elevation angle and motion, and diversity gain achieved by using an antenna array in line-of-sight (LOS) and shadowing scenarios. For typical environments, such as LOS and light or heavy shadowing cases, the experimental results reveal rich spatial diversity and high diversity gain when using a smart antenna system in LEO S-PCS.