Mobile Satellite Communication Systems Research Articles

Convergence of terrestrial and satellite mobile communication systems: an operator's perspective

The rapid growth of innovation, development and convergence in the mobile communications industry has led to immense complexities in proposing business models for the future. The terrestrial mobile communications industry has seen rapid development in new air interface standards in contrast to the Mobile Satellite Systems (MSS) industry. From a terrestrial operator's perspective, this rapid development of new standards poses a threat to the currently deployed mobile network infrastructure. From an MSS operator's point of view, this rapid growth and subsequent deployment poses a threat to one of its core areas of competences: villages and underdeveloped areas. We present an industry level business model for the convergence of terrestrial and satellite mobile communication industry suitable for both terrestrial and MSS operators' perspective. Based upon the business convergence model, we identify the gaps in convergence, using 'stakeholder analysis' and identify potential opportunities in addition to filling in the gaps.

Performance of Digital Modulation in Double Nakagami-m Fading Channels with MRC Diversity

In this paper, we derive the average bit error probability (BEP) for common digital modulation schemes and the outage probability of double Nakagami-m channels with MRC diversity. First, the probability density function (PDF) and moment generating function (MGF) of received signal with maximal ratio combining (MRC) receiver diversity are computed. The derived MGF results are simplified in terms of a generalized hypergeometric function 2F0. The derived BEP expressions find applications in existing wireless systems such as satellite mobile communication system, mobile-to-mobile communication system and multiple-input multiple-output (MIMO) wireless communication system. In addition, the obtained general MGF expression considers combined Rayleigh × Nakagami-m, double Rayleigh, single Rayleigh, single Nakagami-m, and non-fading or additive white Gaussian noise (AWGN) channels as special cases. The simulation results agree well with the theoretical results.

An Improved Power Estimation for Mobile Satellite Communication Systems

In this paper, in order to increase system capacity and reduce the transmitting power of the user's equipment, we propose a efficient power estimation algorithm consisting of a modified open-loop power control (OLPC) and closed-loop power control (CLPC) for mobile satellite communications systems. The improved CLPC scheme, combining delay compensation algorithms and pilot diversity, is mainly applied to the ancillary ter-restrial component (ATC). ATC link in urban areas, because it is more suitable to the short round-trip delay (RTD). In the case of rural areas, where ATCs are not deployed or where a signal is not received from ATCs, transmit power monitoring equipment and OLPC schemes using efficient pilot diversity are combined and ap-plied to the link between the user's equipment and the satellite. Two modified power control schemes are ap-plied equally to the boundary areas where two kinds of signals are received in order to ensure coverage conti-nuity. Simulation results show that the improved power control scheme has good performance compared to conventional power control schemes in a geostationary earth orbit (GEO) satellite system utilizing ATCs.

Potential Benefits of Dynamic Beam Synthesis to Mobile Satellite Communication, Using the Inmarsat 4 Antenna Architecture as a Test Example

Present mobile satellite communication systems use large antennas to provide multiple high-gain beams. Each beam covers a fixed geographic cell on the earth. Spatial frequency reuse is provided by synthesising beams with low-power levels over all cells operating at the same frequency. The performance needs for future systems are steadily increasing, leading to higher-gain requirements, which are met by using larger antennas with narrower beams. So the antenna pointing errors become a significant loss factor. An alternative approach is to abandon the use of fixed beams and dynamically synthesise the beams to optimise the antenna performance in real time. This both increases user gain and lowers cofrequency interference whilst also reducing the effects of pointing errors. Simulations, using the Inmarsat 4 antenna architecture as a test example, show that the spatial isolation performance can be significantly improved by using Dynamic Beam Synthesis.

Modified Power Control Algorithms for Mobile Satellite Communication Systems with ATCs

In this paper, in order to increase system capacity and reduce the transmitting power of the user's equipment, we propose a modified power control scheme consisting of a modified closed-loop power control (CLPC) and open-loop power control (OLPC). The modified CLPC algorithm, combining delay compensation algorithms and pilot diversity, is mainly applied to the ancillary terrestrial component (ATC) link in urban areas, because it is more suitable to the short round-trip delay (RTD). In the case of rural areas, where ATCs are not deployed or where a signal is not received from ATCs, transmit power monitoring equipment and OLPC algorithms using efficient pilot diversity are combined and applied to the link between the user's equipment and the satellite. Two power control algorithms are applied equally to the boundary areas where two kinds of signals are received in order to ensure coverage continuity. Simulation results show that the modified power control scheme has good performance compared to conventional power control schemes in a geostationary earth orbit (GEO) satellite system utilizing ATCs.

Optimal reassignment-based complex nonlinear processing of vector discrete-continuous Markovian random processes

Methods of the Markovian estimation theory are applied to the synthesis of optimal and quasi-optimal algorithms that involve time-stepped reassignment of the values of the parameters of conditional a posteriori probability densities of filtered continuous processes. The algorithms are intended for nonlinear processing of a vector discrete-continuous Markovian random process whose continuous component is a vector diffusion Markovian process and whose discrete component is a two-component vector, each component of which is characterized by a simple several-position Markovian chain. It is assumed that one group of simultaneously processed signals is observed against the background of colored (time-correlated) noise, while the other group is observed in the presence of white Gaussian noise. Basic analytic relationships and the corresponding block diagram of a system for quasi-optimal complex nonlinear processing of signals typical of the GLONASS, GPS, Galileo, and QZSS satellite navigation systems and such satellite mobile-communications systems as the Globalstar system are presented.

A self-verification authentication mechanism for mobile satellite communication systems

In order to provide an opportunity to make personal communication as broad as possible, mobile satellite communication systems have recently drawn much attention. However, any communication system raises two major challenging issues: (1) how to determine whether actors are whom they claim to be; and (2) how to protect data against unauthorized disclosure. Although the secret-key cryptosystem (SKC) and the public-key cryptosystem (PKC) have been developed to provide well-defined security services to address these issues each has serous drawbacks while SKC-based authentication schemes have the common demerit that the server which maintains the secret-key table becomes an attractive target for numerous intrusions, PKC-based schemes suffer from the expensive complexity of the public-key infrastructure (PKI) and a high computation overhead. Therefore, in this paper, a self-verification authentication mechanism with lower computation and key management cost is introduced.

A novel approach to model the land mobile satellite channel through reversible jump markov chain monte carlo technique

A key issue in the design of a mobile satellite communication system is an adequate knowledge of the statistical behavior of the propagation channel. To achieve this goal, the development of very accurate models plays a very important role. In contrast to traditional multi-state Markov chain based models, the novel approach proposed in this paper makes no prior assumptions on the number of states or on the statistical distributions characterizing each state. The sequence of channel states is blindly estimated using a Reversible Jump Monte Carlo Markov Chain algorithm.

Deformed Antenna Pattern Compensation Technique for Multi-Beam Antennas in Broadband and Scalable Mobile Communications Satellites

To create a next-generation mobile satellite communication system that offers large communication capacity, the onboard antenna system must be a multi-beam system consisting of a light weight 20-m class reflector and a light weight 100-beam class antenna feed system. We clarify that the antenna gain decrease created by the reflector surface distortion expected in orbit is relatively large. This paper presents a deformed antenna pattern compensation method that minimizes circuit scale. Validity of the proposed method is confirmed by antenna pattern calculations and experiments on a fabricated array-fed reflector antenna.

Analysis on Connectivity of Inter-Orbit-Links in a MEO/LEO Double-Layer Satellite Network

As an important scheme of future global mobile satellite communication systems to provide multimedia service, a Double-Layer Satellite Network (DLSN) with MEO satellites and LEO satellites is proposed. The Inter-Orbit-Links (IOLs) between layers is an essential factor, which affects the performances of the DLSN systems. Considering certain constellation parameters, the geometric characteristics of IOLs are described and the connectivity of MEO satellites and LEO satellites in the DLSN is analyzed. By computer simulation, the results show that IOLs should be selectively established according to certain parameters rather than the simple in-sight principle.

Signal-detection and signal-processing algorithms for code-division multiple-access satellite mobile communications systems employed simultaneously with satellite radio navigation systems

The Markovian theory of random process estimation is applied to synthesize optimal (and close to optimal) algorithms with discrete-parameter feedbacks. The problem is solved in the case when it is necessary to provide for detection and complex nonlinear processing of discrete-continuous noiselike signals used in code-division multiple-access satellite mobile communications systems employed simultaneously with satellite radio navigation systems. It is assumed that the discrete part of a discrete-continuous state vector to be estimated contains two components, each being characterized by a multiposition simple Markovian chain and that desired signals are observed in the presence of additive partially colored (correlated) Gaussian noises.

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.

Layer 3 Diversity Reception Technology for Ku-Band Mobile Satellite Communication Systems

We describe a layer 3 diversity reception scheme that enhances the transmission characteristics of Ku-band mobile satellite communication systems. This scheme can realize high-speed communication for vehicles that experience shadowing caused by terrestrial obstacles such as tunnels, buildings and bridges, especially for trains that frequently experience shadowing from the trolley wire structures. Layer 3 diversity was chosen for long distance diversity to prevent signal shadowing caused by terrestrial obstacles while minimizing the alterations of existing receivers. The technology enables high-speed communication under shadowing conditions in a running train environment.

Broadband and scalable mobile satellite communication system for future access networks

Due to the recent market trends, NTT has begun research into next generation satellite communication systems, such as broadband and scalable mobile communication systems. One service application objective is to provide broadband Internet access for transportation systems, temporal broadband access networks and telemetries to remote areas. While these are niche markets the total amount of capacity should be significant. We set a 1-Gb/s total transmission capacity as our goal. Our key concern is the system cost, which means that the system should be unified system with diversified services and not tailored for each application. As satellites account for a large portion of the total system cost, we set the target satellite size as a small, one-ton class dry mass with a 2-kW class payload power. In addition to the payload power and weight, the mobile satellite's frequency band is extremely limited. Therefore, we need to develop innovative technologies that will reduce the weight and maximize spectrum and power efficiency. Another challenge is the need for the system to handle up to 50 dB and a wide data rate range of other applications. This paper describes the key communication system technologies; the frequency reuse strategy, multiplexing scheme, resource allocation scheme, and QoS management algorithm to ensure excellent spectrum efficiency and support a variety of services and quality requirements in the mobile environment.

An efficient authentication protocol for mobile satellite communication systems

Nowadays, wireless communication becomes more and more popular. In 2003, Hwang et al. proposed an authentication scheme for mobile satellite communication systems. However, their proposed scheme lacks efficiency and perfect forward secrecy. Thus, we propose an efficient authentication protocol and also present another version for updating the session key to provide perfect forward secrecy in this paper.

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.

High-Speed Satellite Mobile Communications: Technologies and Challenges

Central features of future 4G mobile communication systems are high-speed data transmission (up to 1 Gb/s) and interactive multimedia services. For effective delivery of these services, the network must satisfy some stringent QoS metrics, defined typically in terms of maximum delay and/or minimum throughput. Mobile satellite systems will be fully integrated with the terrestrial cellular systems to provide ubiquitous global coverage to diverse users. The challenges for future broadband satellite systems, therefore, lie in the proper deployment of state-of-the-art satellite technologies to ensure seamless integration of the satellite networks into the cellular systems and its QoS frameworks, while achieving, as far as possible, efficient use of satellite link resources. The paper presents an overview of future high-speed satellite mobile communication systems, the technologies deployed or planned for deployment, and the challenges. Focusing in particular on nonlinear downlink channel behavior, shadowing and multipath fading, various physical channel models for characterizing the mobile satellite systems are presented. The most prominent technologies used in the physical layer, such as coding and modulation schemes, multiple-access techniques, diversity combining, etc., are then discussed in the context of satellite systems. High-speed and QoS-specific technologies, such as onboard processing and switching, mobility and resource management, IP routing and cross-layer designs, employed in the satellite systems are also discussed.

鉄道車両に搭載された衛星追尾アンテナのプログラム追尾の実現性に関する検討

We have proposed mobile multimedia satellite communication system designed to realize high-speed multimedia communications. This system uses a mobile network for the return link and the developed satellite-tracking antenna that receives high-speed satellite signals for the forward link. The satellite-tracking antenna, which consists of four planar antennas, measures the pointing error by the phase monopulse and has achieved the satellite-tracking control by the co-phasing combining and the mechanical drive. When the satellite-tracking antenna is applied to the car and the ship, it is necessary to decide the tracking drive angle constantly. When it is applied to the train, the satellite-tracking can be expected to be achieved by specifying the tracking drive angle in accordance with the distance because the train runs in the same route. This tracking method is called a program tracking in this paper. This paper describes the tracking drive angle and the error factor of the program tracking quantitatively. We concluded that it was possible to apply the program tracking to the train if operating rate of the system was 70% or less.

Impact of buildings on the performance of MEO satellite mobile communication systems for low bit rate applications

Mobile communications for low bit rate applications via midearth orbit (MEO) satellites are considered. Owing to multipath interference, fading of the received signal appears in low bit rate applications. The received signal levels, at the mobile in the presence of buildings, are calculated using the uniform theory of diffraction (UTD) for horizontal and vertical polarisations. Buildings are considered in both residential and moderate urban environments.For easy reference, explicit mathematical representations with illustrations of all significant ray contributions are given. Furthermore, the signal levels data, extracted from the electromagnetics computations, are used to evaluate communication system performance in terms of bit error rate and depolarisation of the received signal. Moreover, computed results are in agreement with actual measured data.

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.