Teletraffic modeling for personal communications services

This article presents a realistic teletraffic modeling framework for personal communications services. The framework captures complex human behaviors and has been validated through analysis of actual call and mobility data. Using the proposed framework, a large-scale simulation was performed on a model of the San Francisco Bay area. Simulation results showing the performance of IS-41 are presented     

EuroBridge: communications services for multimedia applications

The aim of the EuroBridge project is to provide a uniform communication service platform. This platform will provide true multimedia multipoint services including interactive video conferencing and store-and-forward data services. The project will enhance selected OSI application layer services to provide them with multimedia capabilities. Selection of the initial services as well as the identification of necessary functional enhancements were based on actual user requirements. To support the dedicated communication requirements imposed by multimedia and multipoint applications, the lower layers of the OSI model will be enhanced accordingly. This includes designing and implementing new lightweight session and presentation protocols, respectively. Furthermore, high-speed transport protocols will be utilised. The actual protocol stack used will be configured dynamically depending on the requested quality of service. Support of multicast capabilities will be a crucial issue. The service platform is being implemented to run on top of different high-speed networks, including FDDI and DQDB     

Distributed call processing for personal communications services

The authors present a control architecture, procedures, and a signaling system to support advanced personal communication services (PCS). They describe the current cellular system architecture, and its algorithms and data management schemes for providing services. They present review how current cellular systems operate with a focus on mobility management and call and connection control. The benefits of this architecture include lower signaling traffic over wireless links, lower network load for signaling traffic, low call/connection delivery times, ubiquitous service offering, and more efficient routing of connections     

Efficient spectrum allocation for personal communications services

Principal features of personal communications service (PCS), namely, ubiquity, portability, and integration of voice and data, are examined, highlighting some issues affecting the spectrum choices before today's policymakers. Spectrum issues are discussed, focusing on two tools for promoting efficient spectrum use: the use of generic service definitions and band assignment     

Providing multimedia communications services from high altitude platforms

System level design considerations for high altitude platforms operating in the mm‐wave bands are examined. Propagation effects in these bands are outlined, followed by a brief introduction to different platform scenarios. Ground‐based and platform‐based fixed wireless access scenarios are considered, and it is shown that using a platform, a single base station can supply a much larger coverage area than a terrestrial base station. The effects on performance of platform displacement from its desired location with both fixed and steerable antennas are also examined. It is shown that steerable antennas are of most use when fixed stations are immediately below the platform, with no benefit for fixed stations on the edge of coverage. The bandwidths required to serve several traffic distributions (suburbs and city centre based) are evaluated using the Shannon equation. It is shown that capacity can be constrained when users are located in the city centres, despite longer line of sight paths to users out in the suburbs. The effects of temporal changes in the spatial traffic distribution are investigated. It is shown that bandwith requirements can be reduced if the platform moves to track these changes. Copyright © 2001 John Wiley & Sons, Ltd.     

Heterogeneous personal communications services: integration of PCSsystems

Personal communications services (PCS) are being introduced to offer ubiquitous communication. In its first phase PCS consists of a plethora of systems that address cellular, vehicular, cordless phone, and a variety of other services. The integration of these different systems is referred to as “heterogeneous PCS (HPCS)”. We describe the various PCS systems available and address in detail the issue of PCS systems integration. Key implementation issues for integrating PCS systems are defined and discussed     

Call admission control for CDMA mobile communications systems supporting multimedia services

The call admission control (CAC) belongs to the category of resource management. Since the radio spectrum is very scarce resource, CAC is one of the most important engineering issues for mobile communications. In this paper, we propose a CAC scheme for direct sequence code-division multiple-access cellular systems supporting mobile multimedia communications services. There are multiple call classes in multimedia services and the required signal-to-interference ratio (SIR) varies with call classes. Call admission decision in the proposed scheme is based on SIR measurement. We take account of the traffic asymmetry between uplink and downlink, which is the most important characteristic of multimedia traffic. In addition, the proposed scheme guarantees the priority of handoff call requests over new call requests. We evaluate the performance of the proposed scheme using Markov analysis. The performance measures which we focus on are the system throughput and the blocking probabilities of handoff calls and new calls. The outage probability of a call in progress is also calculated, which is the probability that the measured bit energy-to-noise density ratio of the call is smaller than the required value for maintaining adequate transmission quality. We present some numerical examples with practically meaningful parameter values and, as a result, show that the proposed CAC scheme can operate well in the mobile multimedia systems such as the International Mobile Telecommunications-2000 (IMT-2000) systems.     

Next generation satellite systems for aeronautical communications

U.S. airspace is reaching its capacity with the current air traffic control (ATC) system. The number of flights is constantly rising and it is estimated to be over 58 million per year by 2005. The FAA has undertaken several projects to modernize the National Airspace System (NAS) to ensure the safety of the increasing number of flights. Of special importance is the modernization of the air–ground communications infrastructure, which is the heart of the ATC. The current plan in the modernization of the air–ground communications is to migrate from analog voice only system to integrated digital voice and data system. The next generation satellite systems can be an alternative to the terrestrial air–ground systems by their low propagation and transmission delays, global coverage, high capacity and free flight suitable characteristics. In this paper, we give an overview of the current and the future ATC architectures, describe the systems and the communications issues in these systems and develop a framework in which next generation satellite systems can be integrated to the future ATC systems. Copyright © 2004 John Wiley & Sons, Ltd.     

Technologies for multimedia communications

A number of technologies-based upon the sensory modalities of sight, sound, and touch-are becoming well enough established that their coordinated application can expand capabilities for human/machine interaction. This paper examines evolving advances in natural language communication with machines, video, and audio compression, spatially realistic conferencing, tactile interaction, and high-speed data communication. It considers the integration of these technologies into networked information systems to achieve synergistic benefits for the human user     

NGN与多媒体通信

多媒体业务将是电信网络运营商新的利润增长点。现从下一代网络（NGN）的特点与结构出发，分析了NGN的分层结构，结合现存网络体系给出一种完整的NGN多媒体解决方案，解决了在NGN上实现多媒体业务的有关技术问题。最后指出了NGN有待于解决的若干问题以及下一步的主要工作。     

Keeping personal communications personal

In this article, we will focus our attention on the development and utilization of several types of cipher systems, since the use of a code system is typically impractical for hiding the meaning of messages in a rapidly changing corporate environment.     

Corporate multimedia communications

IP-based communications technology will enable people to work in a virtual way and from anywhere in the world. This is already true for data services and applications where IP has become the universal networking technology. Although voice over IP is still a relatively new technology, it has laid the path for new and innovative voice and multimedia communications. This paper looks at new and emerging technology that will tempt business and corporate organisations to adopt IP as a single communications infrastructure for both data and real-time communications.     

Intelligent video smoother for multimedia communications

Multimedia communications often require intramedia synchronization for video data to prevent potential playout discontinuity resulting from network delay variation (jitter) while still achieving satisfactory playout throughput. In this paper, we propose a neural network (NN) based intravideo synchronization mechanism, called the intelligent video smoother (IVS), operating at the application layer of the receiving end system. The IVS is composed of an NN traffic predictor, an NN window determinator, and a window-based playout smoothing algorithm. The NN traffic predictor employs an on-line-trained back-propagation neural network (BPNN) to periodically predict the characteristics of traffic modeled by a generic interrupted Bernoulli process (IBP) over a future fixed time period. With the predicted traffic characteristics, the NN window determinator determines the corresponding optimal window by means of an off-line-trained BPNN in an effort to achieve a maximum of the playout quality (Q) value. The window-based playout smoothing algorithm then dynamically adopts various playout rates according to the window and the number of packets in the buffer. Finally, we show that via simulation results and live video scenes, compared to two other playout approaches, IVS achieves high-throughput and low-discontinuity playout under a mixture of IBP arrivals     

Satellite systems for personal communications

A number of industry groups are planning to construct satellite systems that will provide a personal communications service (PCS) (typically voice, data, and fax) to users over small, hand-held, cellular-type telephones. Some of these systems (e.g., Iridium and Globalstar) will be constructed using satellites in low Earth orbit. Two (Ellipso and ICO) will employ medium Earth orbit (3-8-h period), and still others (ACeS and Agrani) will operate from geostationary altitude. The origin and evolution of mobile satellite communications is discussed first, including the Inmarsat system and several land-based mobile satellite systems in operation. The rival approaches to the PCS market are then described, and some of the technical challenges inherent in each are indicated. This paper concludes with speculation on the factors influencing the likelihood of business success for the various PCS systems     

Satellite systems for personal communications

A number of industrial groups are planning to construct satellite systems to provide personal communications services (typically voice, data, and fax) to users who will employ small, hand-held, cellular-type telephones. Some of these systems (e.g., Iridium and Globalstar) will be constructed using satellites in low Earth orbit. Two (Odyssey and ICO) will employ medium Earth orbit (six-hour period), and still others (ACeS and Agrani) will operate from geostationary altitude. The origin and evolution of mobile satellite communications is discussed first, including the INMARSAT system and several land-based mobile satellite systems in operation. The rival approaches to the personal communications services (PCS) market are then described, and some of the technical challenges inherent in each are indicated. The paper concludes with speculation on the factors influencing the likelihood of business success for the various PCS systems     

An aeronautical multimedia service demonstration at highfrequencies

An aeronautical measurement campaign for the satellite channel at the K band and an aeronautical multimedia service demonstration campaign for high data rate satellite services at the K/Ka band aim to provide high data rate services for all kinds of mobile terminals     

Speech codecs for personal communications

Some of the many factors that go into the design of a personal communications system (PCS) are considered. The ways in which these factors affect the speech codec are discussed. Cell size, multiple access methods, and the trade-offs in PCS design are examined. Possible future designs of PCSs and their codecs are described     

Switching for IP-based multimedia satellite communications

This paper discusses the structure and performance of an Internet protocol (IP)-based satellite communications system to provide multimedia services. Uplink scheduling and switching to support IP differentiated services (DiffServ) traffic in a multibeam environment are addressed. End-to-end performance of a multibeam satellite communications system using an on-board switch is evaluated using simulation. Aggregate real-time and non-real-time traffic using different DiffServ classes is considered and the effects of their burstiness and long-range dependent behavior on the queueing performance are examined. Multiple-frequency time-division multiple-access is used on the uplink in conjunction with a dynamic capacity allocation scheme. Higher priority is given to voice and video real-time traffic to avoid delay variation. On-board downlink queue for non-real-time traffic is provided to achieve high statistical multiplexing gain.     

A comparison study of the two-tier and the single-tier personal communications services systems

A two-tier PCS system integrates the high tier PCS system and the low tier PCS systems into a single system to provide the advantages of both tiers. Such a system is expected to provide better service (more available and more cost effective to the users) at the expense of the extra tier switching management. We compare the performance of the two-tier PCS system and the single low tier system in two aspects: the registration traffic and the service availability. Because of the tier management, the two-tier system generates more registration traffic than the single low tier system. Under the range of the input parameters in our study, we show that the two-tier system generates less than 10% extra registration traffic than the single low tier system in most cases and generates less than 20% registration traffic in the worst cases. It is clear that for the service availability, the two-tier system is better than the single one tier system. We also study the probability that a call is forced terminated in the single low tier system because the low tier becomes unavailable during the call (such a call can be continued in the two-tier system).     

Bandwidth-efficient wireless multimedia communications

Commencing with a brief history of mobile communications and the portrayal of the basic concept of wireless multimedia communications, the implications of Shannon's theorems regarding joint source and channel coding for wireless communications are addressed. Following a brief introduction to speech, video, and graphical source coding as well as the cellular concept, a rudimentary overview of flexible, reconfigurable, mobile radio schemes is provided. We then summarize the fundamental concepts of modulation, introduce an adaptive modem scheme, and argue that third-generation transceivers might become adaptively reconfigurable under network control in order to meet backward compatibility requirements with existing systems and to achieve best compromise among a range of conflicting system requirements, complexity and power consumption, robustness against channel errors, etc