Wireless loops: What are they?

Several loop applications of wireless technology are aimed at reducing the cost of deploying communications services ranging from telephone to wideband video. In these applications, wireless links replace a portion of a wireline loop from a central location (a central office or cable headend) to a subscriber. The replacement of labor-intensive wireline technology by complex mass-produced integrated electronics in wireless transceivers is projected to reduce the overall cost of the resulting loop. These wireless loop applications attempt to provide existing communications services or small modifications to existing communications services. A different interpretation of a wireless loop makes use of low-power digital radio technology to provide the last thousand feet or so of a loop. Low-power low-complexity wireless loop technology in small base units can be integrated with network intelligence to provide the fixed-infrastructure network needed to support economical personal communications services (PCS) to small, lightweight, low-power personal voice and/or data communicators. Low-complexity communicators can provide many hours of “talk time” or data transmission time and perhaps several days of standby time from small batteries (≤ 1.5 oz). Because this application of wireless loop technology can reduce the inherent costs in several parts of a wireline loop, it has the potential to provide convenient widespread PCS at less costs than providing telephone services over conventional wireline loops. This low-power wireless loop application does not fit into any existing communications system paradigm. Wireless technology with tetherless access and wide-ranging mobility, e.g., the personal access communications system (PACS), does not fit the accumulated wisdom of the wireline telephony paradigm. It also does not fit the paradigm of existing cellular radio that has sparsely distributed expensive cell sites, and it is not targeted at fixed video services as is wireless cable. Because a significant change in thinking is required in addressing this new low-power low-complexity widespread wireless loop paradigm, its large economic advantages and service benefits have not yet been embraced by many of the existing communications providers, who appear to be more comfortable pursuing the better-known paradigms of video using wireless cable, or of cellular radio in the guise of high-tier PCS, or in the guise of rapid economical deployment of telephone services in developing nations. This paper discusses the inherent economic advantages and service benefits of low-power low-complexity wireless loop technology integrated with network intelligence aimed at providing economical low-tier PCS to everyone.     

Digital wireless local loop system

The digital access technologies for the wireless local loop (WLL) or fixed wireless system are discussed. WLL is an important means of providing telephone services more cheaply and quickly in the developing countries than through a wireline system. Capacities of a WLL system based on the IS-54 (now IS-136) TDMA, IS-95A CDMA, and ETSI GSM technologies are developed and compared     

Mobile and Multicast IP Services in PACS: System Architecture, Prototype, and Performance

Traditionally, wireless cellular communication systems have been engineered for voice. With the explosive growth of Internet applications and users, there is an increasing demand on providing Internet services to mobile users based on the voice-oriented cellular networks. However, Internet services add a set of radically different requirements on to the cellular wireless networks, because the nature of communication is very different from voice. It is a challenge to develop an adequate network architecture and necessary systems components to meet those requirements.This paper describes our experience on developing Internet services, in particular, mobile and multicast IP services, in PACS (Personal Access Communication Systems). Our major contributions are five-fold: (i) PACS system architecture that provides wireless Internet and Intranet access by augmenting the voice network with IP routers and backbone links to connect to the Internet; (ii) simplified design of RPCU (Radio Port Controller Unit) for easy service maintenance and migration to future IP standards such as IPv6; (iii) native PACS multicast to efficiently support dynamic IP multicast and MBone connectivity; (iv) optimization and incorporation of Mobile IP into PACS handoff mechanism to efficiently support roaming within a PACS network as well as global mobility between PACS networks and the Internet; (v) successful prototype design of the new architecture and services verified by extensive performance measurements of IP applications. Our design experience and measurement results demonstrate that it is highly feasible to seamlessly integrate the PACS networks into the Internet with global IP mobility and IP multicast services.     

On Implementation of Logical Time in Distributed Systems Operating over Wireless Data Networks

We address the problem of maintaining logical time in a distributed system operating over a wireless data network. In such a network a group of mobile nodes currently located in a specific area use services of a mobility service agent to communicate with each other and with the rest of the world. The graph model of the network is represented by fully-connected mesh of star-topology subgraphs. We discuss the complementary logical clocks for the wireline and wireless segment of the network and their integration into an isomorphic logical time system.     

On architectures for broadband wireless systems

The growing popularity of portable and mobile computing and communication devices, along with the introduction of wireline broadband networks, is fueling demand for wireless broadband networks. Since ATM has been accepted as the standard for broadband integrated service networks, the authors consider the problem of providing “ATM-like services” to mobile devices. The fundamental issues that have to be tackled in order to provide broadband services which are currently available (or will be very shortly) to wireline hosts are discussed. The authors compare and contrast the architectures that have been proposed for extending the broadband wireline network infrastructure to the wireless environment. It is argued that transporting small ATM cells over the air leads to inefficient utilization of the already scarce transmission capacity. Subsequently, the authors propose an architecture for integrated wireless and wireline broadband networks which allows the wireline and wireless parts of the network to be designed independently, therefore allowing each to be optimized for the environment in which it operates. At the same time, the proposed architecture also permits simple and efficient interconnection between the wireline and wireless infrastructures     

An efficient algorithm for the link allocation problem on ATM-basedpersonal communication networks

The personal communication network (PCN) is an emerging wireless network that promises many new services for the telecommunication industry. The proliferation of demands for extending wireless services to integrated services which supports the transmission of data and multimedia information has resulted in the need for broadband wireless systems that are able to provide service capabilities similar to those of wireline networks. The ATM cell-relay paradigm is one possible approach to provide broadband wireless transmission with PCNs using the ATM switching networks for interconnection of PCN cells. In an ATM-based PCN, the communication path between a pair of mobile terminals might be elongated due to the mobility of the terminals. The link allocation problem is that of allocating backbone links among ATM switches to reduce the effects of terminal mobility on the performance of ATM-based PCNs. Huang and Wang (1997) have shown that this problem is NP-complete. In this paper, we propose a new efficient heuristic algorithm for the link allocation problem. One novel feature of our algorithm is that we are able to derive sufficient conditions under which our algorithm is able to guarantee optimal solutions. Our empirical study shows that the average lengths of communication paths obtained by our algorithm are shorter than those obtained by Huang and Wang's algorithm. In addition, the number of successfully established paths obtained by our algorithm is significantly more than that obtained by the aforementioned     

Low-tier wireless local loop radio systems. I. Introduction

The article provides the results of a set of analyses conducted to compare two major radio technologies, DECT/PWT-E and PACS, for their suitability in the local loop in the United States to provide voice and data services. DECT, digital enhanced cordless telecommunications, is a radio interface standard developed in Europe mainly for indoor wireless applications and being promoted lately for wireless local loop applications as well. PWT, personal wireless telecommunications, is a DECT-based standard developed by the TIA in the United States for the unlicensed PCS applications. PWT-E, enhanced, is the version that is suitable for the licensed PCS applications. PACS, personal access communications systems, is a total system standard (i.e. radio interface and associated network infrastructures) developed in the United States for licensed PCS applications. (PACS-UA and PACS-UB are the standards for the unlicensed PCS applications.) For the wireless local loop (WLL), we make an assumption that the radio technologies operating in the licensed PCS spectrum are more suitable to provide a quality of service that is expected traditionally from a local exchange company (LEC). Therefore, this article focuses on the PACS and PWT-E, rather than PACS-UB and PWT. Also note that the article focuses on the North American version, PWT-E, rather than the European version, DECT. It provides an introduction to the PACS and PWT technologies     

WiMAX应用潜力分析

文章分析了WiMAX在固定宽带无线接入场合和便携、移动通信场合的应用前景.文章认为:在固定宽带无线通信中,WiMAX会广泛应用于家庭用户、IP语音用户、传输承载用户和集团客户,为他们提供宽带无线接入;在便携、移动通信中,IEEE802.16即将集成到笔记本电脑和个人数字助理(PDA)等便携式电子设备中,实现在城域网范围内的可移动的宽带无线数据服务;用户需求加上WiMAX设备的批量上市及终端成本的下降,WiMAX的应用潜力巨大,市场将呈几何级增长.     

A survey on wireless ATM technologies and standardization

Growing emphasis on multimedia traffic has underlined the importance of broadband asynchronous transfer mode (ATM) networks which are capable of supporting demanding applications such as audio/video playback, image browsing, real-time voice/video transmission and interactive data exchange in a unified manner. However, the extension of ATM from wireline to wireless creates a new set of challenging issues. ATM standards are developed based on high data rates and reliable transmission links. This is in contrast to wireless channels where bandwidth is limited and error rates are high. Furthermore, existing ATM specifications are designed primarily to provide services to fixed end-terminals with little ability to adapt to mobile connections and the highly time-varying conditions associated with wireless networks. This paper surveys the major technical and service issues related to the deployment of ATM in third-generation wireless networks. It will also cover how international standards are progressing in this important area. This revised version was published online in August 2006 with corrections to the Cover Date.     

Location-Independent Access in Mobile Systems

In this paper, we report on the design of a protocol for transparent, location-independent access in mobile systems. The protocol, termed by us Mobile Client/Server Protocol (MCSP) is an implementation of a communication layer on a mobile host and a stationary machine within the wireline network, and provides middleware functionality. The MCSP supports communication services through the client/server paradigm to transaction-oriented applications distributed between the mobile and a set of service and information brokers. To support the mobile and the wireless environment, a surrogate process is created within the fixed network to perform operations on behalf of the mobile within the fixed network. The MCSP then loosely couples the communicating entities, thus reducing the overhead associated with handoffs and disconnects, so characteristic of the mobile environment. Of particular interest is the application of the MCSP to location-based services, for example, the Intelligent Vehicle Highway Systems [1].     

Aggregate History of User Mobility Pattern for QoS Provisioning in Multimedia Wireless Networks

Multimedia traffic is expected to be included in the next generation of wireless networks. As in wireline networks, the wireless network must also be capable of providing guaranteed quality-of-service (QoS) over the lifetime of mobile connections. In this paper, a bandwidth reservation scheme incorporating a user mobility prediction is proposed to manage the QoS of the networks. The mobility prediction scheme is developed based on the aggregate history of mobile users. Based on the mobility prediction, bandwidth is reserved to guarantee the uninterrupted handoff process. Simulation results demonstrate that the proposed scheme can guarantee the required QoS requirements in terms of handoff call dropping probability and new call blocking probability while maintaining efficient bandwidth utilization.     

TD-SCDMA和WiMAX技术融合实现宽带无线移动通信系统

本文主要论述了基于TD-SCDMA和WiMAX技术融合实现一种新型的宽带无线移动通信系统。在该系统中,TD-SCDMA接入网提供广域无线覆盖,支持高移动性,提供话音业务和中、低速数据业务;WiMAX接入网提供热点区域覆盖,支持游牧移动性,提供高带宽流媒体数据服务,两种接入技术在网络层实现汇聚,通过网络层移动性管理技术,共享核心网络和业务系统,实现两种接入网的统一的无线资源管理以及统一的用户管理和计费,移动终端可以在该系统下的两种网络之间实现无缝漫游和切换。该种新型的移动通信系统能够很好的满足用户对移动通信业务的使用要求,也能够有力支持TD-SCDMA大规模独立组网,增强TD-SCDMA的竞争力;同时,也为TD-SCDMA系统的演进和跨越式发展提出新的思路。     

A direct signaling system for flexible access and deployment oftelecommunication services

In current telecommunication networks, the value-added services available to subscribers are almost exclusively offered by the carrier providing local telephony service. This results from two factors: the processing for services is either based in or triggered from software executing on the access telecommunication switches, and signaling links over which subscribers request services are terminated on these access switches. In a direct signaling system, the signaling link from a subscriber does not necessarily terminate on an access switch, but rather on an intelligent server we call a call server. The call server invokes service functions and coordinates their interactions. This direct signaling system may be overlaid on various types of access networks, including circuit-switched telephony, packet telephony, wireless local loop, cable, etc. We discuss the design, implementation, and performance of a direct signaling system, including procedures that provide varying amounts of integration with current telecommunication systems. Our results show that a direct signaling system using a low-delay direct signaling link and in which no changes are made to existing telecommunicatione switches incurs approximately 100 ms higher postdial delay than a standard ISDN system. A direct signaling system in which telecommunication switches provide open interfaces and coordinate processing with direct signaling servers incurs approximately 100 ms lower postdial delay than a standard ISDN system     

RSVP extensions for real-time services in wireless mobile networks

Currently, the RSVP model, which is efficient resource reservation in the fixed endpoints, becomes invalid under host mobility. We investigate the problems of standard RSVP in providing real-time services in wireless mobile networks. We also observe carefully how to interoperate IntServ services over DiffServ networks, and how to map IntServ QoS parameters into a wireless link. We then identify the advantages and drawbacks of the existing RSVP proposals to support QoS under both micromobility and macromobility. We finally propose a dynamic resource allocation scheme for reducing service disruption of real-time applications due to frequent mobility of a host     

Full-Duplex DOCSIS/WirelessDOCSIS Fiber–Radio Network Employing Packaged AFPMs as Optical/Electrical Transducers

A hybrid fiber-radio access network architecture for simultaneous wireline and wireless transmissions of data-over-cable service interface specification (DOCSIS) signals is presented. An all-optical harmonic up-conversion technique using a dual-drive Mach-Zehnder modulator provides the downstream optical signal modulated not only at the intermediate frequency in the 600- to 900-MHz band for wireline transmission but also at the up-converted frequency in the 5.45- to 5.75-GHz band for wireless transmission. An InGaAsP/InGaAsP multiple-quantum-well asymmetric Fabry-Perot modulator/detector has been designed, fabricated, and packaged and has been employed in the base station (BS) as an optical/electrical transducer, simultaneously providing the functions of optical intensity modulation and photodetection. At the BS, the DOCSIS signals are recovered at the wireline and wireless frequencies for the respective feeding of a cable access network or a fixed wireless access network in a highly flexible approach. Full-duplex operation has been demonstrated for both access types in an indoor laboratory environment. In a subsequent small-scale field trial, real-life Internet traffic provided by a local community antenna television system operator has been transported over the present hybrid fiber-radio access network architecture, and simultaneous transmission of both DOCSIS and digital television signals has also been performed.     

无线本地环路技术的发展与市场展望

随着我国电信事业的迅速发展，用户接入已成为人们所关注的问题。无线本地环路技术结合了移动通信和数字通信技术，可快速、经济、灵活地提供业务，是有线通信网的补充和延伸。此项技术正日益引起人们的兴趣。     

Wireless Andrew: Building a High Speed, Campus-Wide Wireless Data Network

Carnegie Mellon University (CMU) has a major program to create a high speed wireless network, known as Wireless Andrew. The first Phase of this network has been operational for over a year and the second Phase, to upgrade this to IEEE 802.11 standard technology, has begun. The Wireless Andrew network uses wireless local area network technology, utilizing spread spectrum in the ISM band. The purpose is not only to support wireless research but also to create a campus-wide mobile computing laboratory.The paper shows the challenge of designing and managing large scale wireless networks. The examples show the differences experienced in wireless versus wireline networks due to the nature of mobility versus static components, the nature of RF propagation versus wireline connection, and the difference in sophistication of tools because of the different place in the product development cycle. The paper describes the lessons learned at completion of the first phase including: installation design issues, issues of RF interference and data throughput, the unique problems of wireless network management, and the release of the system. The paper goes on to describe lessons learned during the first year of operation of the research network. It then discusses experience so far in Phase Two, to create an operational utility for use of all students, faculty, and staff for educational, research, and administrative applications.     

Managing IP services over a PACS Packet Network

We have developed a system and network architecture to provide IP services in the Personal Access Communications System (PACS). IP datagrams are delivered to PACS users through the PACS packet-mode data service, achieving more efficient usage of wireless resources and supporting multimedia applications such as MBone audio and video. The architecture presented in this article augments the PACS voice network with IP routers and backbone links, called the PACS Packet Network (PPN), and is connected to the global Internet via gateways. Compared to the cellular digital packet data (CDPD) network, which employs its own network-layer mobility protocol and thus supports roaming within the CDPD network only, we have incorporated Mobile IP into the PACS handoff mechanism to further achieve global IP mobility. We have also developed native PACS multicast and a group management scheme to efficiently handle dynamic IP multicast and MBone connectivity. These features seamlessly integrate PACS into the global Internet and provide standard-conforming IP services with global mobility     

无线移动网络的综合服务模型与资源预留研究

本文讨论了无线移动网络的综合服务模型,提出应按照服务承诺是否移动相关以及资源是否独占来对实时服务进行分类,并定义了组成该综合服务模型的五种服务承诺.本文同时还讨论了移动无关与移动相关服务的资源预留解决方案,提出在移动无关服务中用移动代理技术建立端-端的主动预留与被动预留,而在移动相关服务中只建立主动的端-端预留并在相关的无线链路上被动预留资源.