How WARC '92 will affect mobile services

The US proposals to, and the decisions of, the 1992 World Administrative Radio Conference (WARC '92) that relate to mobile and mobile-satellite services are described. Mobile-satellite service (MSS) issues addressed at WARC '92 include new allocations for low Earth-orbit (LEO) satellite operations, new MSS spectrum allocations, and modifications to current allocations used to support mobile-satellite operations. Allocation issues on the agenda of WARC '92 that related to the terrestrial mobile services include allocations for mobile services between 1 and 3 GHz, allocations for aeronautical public correspondence, and designation of frequency bands for future public land mobile telecommunications services. A number of proposals which were put forward by the US to support MSS allocations and operations that did not explicitly require allocations to the MSS are discussed     

A novel array antenna for MSAT applications

The issue of reducing the cost of phased array vehicle antennas through the use of a lens feeding arrangement instead of phase shifters at each element is addressed. In particular, the economic viability of a mobile satellite system (MSAT) is largely dependent on the efficient use of the allocated scarce spectrum and orbit as well as the satellite power. The type of vehicle antenna used will play a critical role in achieving this efficiency. A standard design approach for an electronically steered array uses phase shifters at each element to provide beam steering. A method for reducing the required number of phase shifters by using an R-KR lens feed network is outlined. The authors briefly discuss the phase shifter approach to beam steering, examine various lens feed techniques, and describe the R-KR lens approach. The lens feed network architecture is examined, a computer model for simulation of the array is presented, and the results of analysis of a suggested design for the MSAT application are given. In addition, satellite acquisition and tracking considerations are investigated     

国外卫星移动通信新进展与发展趋势

在地面移动通信迅猛发展的新形势下,提供相似业务的卫星移动通信的发展动态和趋势值得关注.首先介绍了国外卫星移动通信市场发展动态,然后分别介绍了静止轨道、中轨道和低轨道三类卫星移动通信系统的最新进展,其中静止轨道卫星移动通信发展最好,中低轨道卫星移动通信系统发展相对不景气;最后探讨了卫星移动通信的发展趋势,指出通过星地集成...     

VSAT networking concepts and new applications development

The authors present some innovative very small aperture terminal (VSAT) technology that can be used to support new applications. The first of these applications explores the possibility of realizing a VSAT-based satellite wide area network (SWAN) to provide flexible interconnection between local area networks (LANs) and metropolitan area networks (MANs) as well as gateway access to centralized information databases and computing services. A second application deals with the potential provision of ISDN-compatible services via VSATs in conjunction with existing satellites as well as future advanced satellites (ADSATs) having onboard switching and processing capabilities. The use of VSATs to solve backhaul interconnection/internetworking problems associated with evolving mobile satellite (MSAT) communication networks is discussed     

Land mobile satellite systems

The general advantages and potential operating characteristics of the mobile satellite service (MSS) are described, and distinctions are made between radio telephone, which is interconnected to the public switched telephone network, and private mobile radio systems. Mobile satellite service offers voice, data, position location, and paging services, interconnection to the public switched telephone network, and the possibility of private networks. Performance and cost characteristics are given along with summaries of market needs and market demands. The space and ground systems of the MSS are described     

A model for interference studies relating to multisatellite non-geostationary systems in the mobile satellite service

An option being considered by current and prospective mobile satellite service (MSS) operators is the use of constellations of non-geostationary orbit (NGSO) satellites to provide global personal communications. The scarcity of free spectrum, together with the bandwidth typically required, means that any new MSS system must consider sharing spectrum with other systems and services. Spectrum sharing must be based on defined interference criteria being satisfied. When multiple NGSO satellites are considered there is no accepted method for assessing interference. This paper describes a model used as the basis for a computer simulation of interference scenarios involving MSS, fixed service (FS) and fixed satellite service (FSS) systems. The simulation includes NGSO dynamics, constellations of MSS satellites with multi-spot antennas, multiple geostationary FSS satellites and multiple hop FS links. Interference events are based on C/I calculations, and statistics, such as the percentage of time that the C/I falls below a required protection ratio, are calculated. More generally C/I cumulative distribution functions are produced.     

PCS global mobile satellites

As the new era dawns in wireless information systems, mobile satellite services (MSS) are emerging as an integral component in what has become the turn-of-the-century global communication network. It is generally agreed that the universal personal communication paradigm is the confluence of terrestrial-based and satellite-based systems. PCS users will neither know nor care if their calls are being carried by satellite or cellular. Unlike their terrestrial-based counterparts. The MSS, with their global blanket coverage, are truly able to realize the vision of communications from anywhere at any time for people on the move. The MSS are also being used in developing countries without existing wireline networks to provide rapid, ubiquitous telephone service. This article provides an overview of mobile satellite systems and concepts. The materials presented are geared toward a broad audience with engineering or management back grounds     

岸船数据传输问题分析和解决

针对岸船间采用多业务交换机(MSS)和双向不对称卫星信道传输数据的问题,通过深入分析研究MSS的接口和协议特性,提出了岸船之间MSS双向不对称中继组网、单向数据传输和低速异步数据传输等特殊应用的解决方案,并通过测试验证了方案的可行性。实现了岸船之间利用一条双向不对称卫星信道传输IP数据、话音、单向/双向电路数据、单向视频和异步数据等综合业务的需求,为工程实施提供了技术指导和依据。     

Mobile satellite system propagation measurements at L-bandusing MARECS-B2

A mobile satellite system (MSS) propagation experiment at 1.5 GHz was performed near the east coast of the United States in central Maryland during December 1987 using the MARECS-B2 satellite as a transmitter platform. A receiving system in a vehicle measured signal fades caused by shadowing and multipath from roadside trees and utility poles. The propagation degradations were characterized for a system of three roads previously examined using a helicopter as the transmitter platform. The objectives of the MARECS-B2 MSS tests were to: (1) establish cumulative fade distributions for the particular satellite geometry for both rural and suburban roads; (2) validate the consistency of previous roadside tree measurements which employed a helicopter as the transmitter platform for the same system of roads; (3) obtain an additional set of fade levels at a lower angle hitherto not measured in central Maryland; and (4) combine the satellite-acquired data set with previous helicopter results and establish an analytic, empirically derived function describing the cumulative fade distributions for a family of path angles. An analysis of the satellite data has demonstrated the successful achievement of these objectives     

Satellite communications systems move into the twenty‐first century

This paper discusses the evolution of communication satellite systems and communications satellite technology from the 1960's to the 1990's. The paper identifies the key attributes of satellite communications that has driven this evolution and now drives the future directions such systems will take. The paper then discusses the future direction of communication satellite systems including DBS, MSS, FSS and hybrid satellite/terrestrial systems. The paper points to the continued evolution of the satellite payload to use of spot beams, onboard processing and switching, and intersatellite links, with capability for higher EIRPs. The paper also identifies the earth station trends to more compact, lower cost stations, produced in higher volumes, with the handheld phone for MSS operation being the prime example of this trend. The paper then points to some revolutionary trends in satellite communication networks being proposed for MSS and FSS applications involving fleets of NGSO satellites combined with more extensive ground networks involving new networking concepts, new services (such as multimedia) and new hybrid configurations working with terrestrial networks, involving a host of new network issues and operations. This revised version was published online in June 2006 with corrections to the Cover Date.     

Trellis coded modulation schemes for shadowed Rician fading channels

The Canadian mobile satellite (MSAT) channel has been modelled as the sum of lognormal and Rayleigh components to represent foliage attenuation and multipath fading, respectively. The paper derives a Chernoff based error bound on the performance of trellis coded modulation (TCM) schemes operating on this channel.<>     

Video image transmission over mobile satellite channels

This paper addresses the transmission of low bit-rate video image sequences through mobile satellite channels to provide portable communications services to remote areas. The particularly challenging aspects of this transmission channel include (1) rapid fading and log-normal shadowing, (2) low signal-to-noise ratio (SNR) due to the noise-limited channel, (3) the satellite's geostationary orbit which incurs a large 250 ms roundtrip propagation delay, (4) limited existing bandwidth near 2 GHz; the video service is to overlay existing Mobile Satellite (MSAT) voice service using a minimum number of 6 kHz (analog bandwidth) channels, and (5) the use of travelling-wave-tube amplifiers which preclude the bandwidth-efficient quadrature amplitude modulation (QAM) proposed for terrestrial high-definition TV (HDTV) broadcast. In the proposed concatenated system, the inner codec is compatible with both voice as well as future-oriented error-resilient, scalable video compression schemes. The key issues are the joint design of on-line channel estimation, soft-decision decoding, trellis-coded modulation (TCM), interleaving depths, and error correcting codes. We have shown through end-to-end bit-level simulation, that highly reliable transmission of 24 and 64 kbps video (H.263) can be realized at 15 and 40.5 kBd, respectively, with low delay, power and modest overall system complexity.     

Demand assignment multiple access and dynamic channel allocationstrategies for integrating radio dispatch and telephone services overmobile satellite systems

The authors discuss the performance analyses of a novel demand assignment multiple access (DAMA) scheme addressing the special characteristics of the mobile radio service (MRS), and a new method for dynamically allocating a common pool of channels to both MRS and mobile telephone service (MTS) to improve channel utilization. The new DAMA scheme makes use of call queuing, batch processing, and pipelined signaling to minimize call setup overhead for MRS traffic. MRS call setup delays were analyzed by simulation modeling of a mobile satellite system (MSS) with many mobile voice-dispatch networks operating over a multiple spot beam satellite to investigate the effects of traffic volume, batch size, and batch service disciplines. A reserved channel margin algorithm for dynamic channel allocation was shown to be effective in harmonizing the different call setup performance requirements for MTS and MRS. Numerical results show that dynamic channel allocation applied to a common pool of 40 channels enables a 20-25% increase in the number of mobile terminals compared with a fixed allocation of 20 channels to each of the two services     

Feasibility of Coexistence of Mobile‐Satellite Service and Mobile Service in Cofrequency Bands

Interference scenarios and methodologies between a terrestrial mobile service (MS) system and mobile‐satellite service (MSS) system in a co‐channel environment are established. Taking into account a practical deployment situation for both systems, we perform computational simulation of interference in terms of carrier‐to‐interference ratio (C/I) and interference‐to‐noise ratio (I/N) to evaluate the cofrequency interference from an MS system into an MSS system, and from an MSS system into an MS system, respectively. The methodology and results can be used as a guide when planning the deployment of MSS and MS systems with no unacceptable interference impact between them.     

卫星气象业务在1670-1710MHz频段应用现状与发展

 卫星气象业务是一种用于气象目的的卫星地球探测业务,在人民的生产、生活中起到极为重要的作用。1670-1710MHz频段是国际电联《无线电规则》划分给卫星气象业务用于数据传输使用的重要频段之一,该频段还同时划分给气象辅助业务、固定业务、移动业务、卫星移动业务等共同使用。本文详细介绍了目前国际上卫星气象业务在这一频段的使用情况、干扰评估准则,并结合我国卫星气象业务的频率使用情况,介绍并研究该频段内卫星气象业务与卫星移动业务、气象辅助业务之间的共用现状与技术,以期给上述业务在该频段未来的发展和使用提供借鉴。     

Symbol-aided plus decision-directed reception for PSK/TCMmodulation on shadowed mobile satellite fading channels

The symbol-aided (SA) synchronization concept developed by Moher and Lodge (1989) is applied to the MSAT channel modeled with a shadowed Rician process. Simulation data demonstrate that it can track the severe phase jitter encountered on the fading channel free of the false lock which plagues conventional techniques. The algorithm multiplexes known symbols into the data stream, establishing an absolute reference free of decision errors that is used to estimate the fading phase. An improvement to the SA algorithm which extracts phase information from the data-bearing symbols is proposed. It is found that the new technique is more effective for larger K. The improved algorithm is referred to as symbol-aided plus decision-directed (SADD) phase estimation. A system employing SADD phase estimation, trellis-coded modulation, interleaving, and amplitude weighting within the Viterbi decoder yielded the best BER performance on the shadowed MSAT channel considered     

Network management for mobile satellite systems

Mobile satellite systems (MSSs) are being developed around the world to provide voice and data services to large populations of mobile subscribers in rural and sparsely populated areas. To maintain efficient operation of an MSS, it is essential that a network management system (NMS) be incorporated into the design. This paper presents a comprehensive review of these issues in relation to the overall requirements of MSSs. Functions that need to be performed by the NMS are discussed in detail, under the categories of configuration, fault, performance, accounting, security, capacity, service, and administration management. An architecture for integrating NMS functions into the network control centre (NCC) and extending network management services to other network elements is presented. The roles of enabling technologies such as expert systems, fault tolerant processors, and objected‐oriented databases are examined. This revised version was published online in June 2006 with corrections to the Cover Date.     

Microstrip Yagi array antenna for mobile satellite vehicleapplication

A novel antenna structure formed by combining the Yagi-Uda array concept and the microstrip radiator technique is discussed. This antenna, called the microstrip Yagi array, has been developed for the mobile satellite (MSAT) system as a low-profile, low-cost, and mechanically steered medium-gain land-vehicle antenna. With the antenna's active patches (driven elements) and parasitic patches (reflector and director elements) located on the same horizontal plane, the main beam of the array can be tilted, by the effect of mutual coupling, in the elevation direction providing optimal coverage for users in the continental United States. Because the parasitic patches are not connected to any of the lossy RF power distributing circuit the antenna is an efficient radiating system. With the complete monopulse beamforming and power distributing circuits etched on a single thin stripline board underneath the microstrip Yagi array, the overall L -band antenna system has achieved a very low profile for vehicle rooftop mounting, as well as a low manufacturing cost. Experimental results demonstrate the performance of this antenna     

US Air Force communications in Desert Storm

The US Central Command Air Forces' (USCENTAF) communications network for Operations Desert Shield and Desert Storm is described. The Central Command Air Forces network utilized 27 SatCom terminals, 27 automatic switches, and 27 terrestrial links and had the responsibility of providing air traffic services across six countries at 24 locations handling 350000 flight operations. The system complexity and air traffic operations, satellite transmission system, terrestrial transmission system, and voice switched network are discussed     

Hybrid satellite and terrestrial networks

The role of satellite communications in networks that provide new services, such as frame relay and multimedia, is investigated. Both passive and active (on-board switching/processing) satellite systems are considered. Novel techniques are developed for each system to demonstrate, via detailed analysis and simulation, how the communications bandwidth agility of multipoint/broadcast satellite channels, and the on-board switching/processing, makes it feasible to provide these new services via hybrid satellite and terrestrial networks in a resource-efficient manner.