Fixed wireless access: a market and system overview

Amongst the many technological developments of the last few years, one in particular has been directly driven by the liberalisation of the telecommunication services sector and the entry of competition into once monopoly markets. That technology is fixed wireless access (FWA). While traditional telecommunication infrastructures have relied on the use of twisted pair copper wire to deliver services to subscribers-the local loop-FWA replaces this with point-to-multipoint digital wireless links. This paper examines the history of Nortel's involvement as market leader in this sector from its earliest days, the approaches the company has taken to the technologies involved and explores FWA's potential in the world's deregulating telecommunication services market     

固定无线宽带接入技术

1无线接入网概述 无线接入网又称为无线本地环路(WLL),由无线基站和用户单位组成.无线基站包括基站收发信机、基站控制器,它提供一个面向程控交换机的标准网络接口V5接口和面向用户侧的空中接口,并完成无线接口的认证和保密、无线资源管理、用户单位登记、路由选择、计费维护以及协议转换、语言与数字的代码转换等功能.用户单元包括收发信机,并提供一个面向基站的无线接口和而向用户的传统接口.传统接口实现协议转换、代码转换、认证、本地供电等功能.交换机与基站之间用数字传输系统相连.基站把网络侧进来的复合网络标准的数字信号,转换成数字空中接口信号.用户单元接收机站送来的无线信号,并将其转换成为模拟信号或者标准数字信号,再用有线手段与用户设备相连.     

Fixed wireless routes for Internet access

The author discusses the use of fixed radio access in urban and rural locations for Internet access. The costs involved are discussed and compared to wired access costs. The frequency bands available are considered as are the propagation conditions and antenna aspects     

An overview of MIMO-oriented channel access in wireless networks [medium access control protocols for wireless LANs]

The integration of MIMO technology in WLANs has recently been the locus of extensive research. The main objectives of this technology are to improve channel reuse and or reduce energy consumption. In this article, we give an overview of MIMO systems and their use in WLANs. We highlight the different types of gains that MIMO offers and then discuss some of the work that has been done on MAC design. We conclude by outlining several open issues thai must be addressed for MIMO-based systems.     

Fixed low-frequency broadband wireless access radio systems

This article provides an overview of a fixed low-frequency broadband wireless access system for point-to-multipoint voice and data applications. The operating frequency bands are from 2 to 11 GHz, and the base station can use multiple sectors and will be capable of supporting smart antenna technology. The product system requirements, design of the radio subsystem specification, as well as an analysis of microwave transmission related to current radio technologies are presented. Examples of BWA technology are provided courtesy of Harris Corporation     

宽带固定无线接入技术与未来发展

宽带固定无线接入被认为是新兴电信运营商解决“最后 一公里”接入问题的首选技术，本文综述了宽带固定无线 接入技术的发展现状、竞争环境以及几个主要的代表技术， 并分析了其未来获得良性发展的几个关键因素和策略。     

An overview of the standardisation in the area of the broadband fixed wireless access

The broadband fixed wireless access systems will be subject to an increasing development during the next years; these systems will allow to offer the subscriber a full set of services, from the conventional narrow band applications up to the emergent broadband services like Internet access, or leased lines. This rapid growth has carried several initiatives in the telecommunications standardisation bodies, like ETSI in Europe, IEEE in North America, or ITU at international level. These initiatives resulted in the creation of ad hoc groups, for instance the BRAN/Hiperaccess project of ETSI, the IEEE 802.16, or the jrg 8A-9B in ITU standards resulting from this activity are expected in 2000/2001. In parallel to this standardisation activity it appeared necessary to designate, or at least to recommend, dedicated frequency bands for fixed wireless access (fwa) or multimedia wireless systems (mws) applications. In order to satisfy this need the regulation authorities, especially the CEPT in Europe, are preparing decisions and recommendations which are expected to favour a certain level of harmonisation in the use of the spectrum by fwa or mws systems.     

An overview of wireless broadband communications

A brief overview of wireless broadband communication systems, those providing a data rate higher than 2 Mb/s and up to 155 Mb/s, is done by addressing some of the applications and services that are foreseen, as well as some of the technical challenges that need to be solved, and by referring to some safety considerations. After an introduction, the need for high data rates is justified, and possible applications are listed and compared, concerning user mobility and bandwidth. Then an analysis of the propagation aspects at the bands foreseen for these systems-microwaves, millimeter waves and infrared-is presented, also addressing the issue of the antennas and batteries for these systems     

An overview of broad-band access technologies

The provision of broad-band services based on either the Internet or the asynchronous transfer mode (ATM) technique requires a new generation of access networks. In the short term, solutions such as x-digital subscriber line (DSL) and hybrid fiber coaxial (HFC), allowing the reuse of existing infrastructures look very promising. For the longer term, new infrastructures based either on radio or on optical access links seem preferable. Three x-DSL techniques aiming at high-bit-rate transmission over twisted pairs are presented: high-bit-rate DSL, asymmetrical DSL, and very-high-bit-rate DSL. An extension of existing cable television networks known as HFC is also described. Two other prospective approaches, wireless in the loop (WITL) and fiber in the loop (FITL), are then presented. Several techniques are considered for WITL: digital enhanced cordless telecommunication local multipoint distribution service, wireless ATM, and low Earth orbit satellite constellations. The various architectural alternatives for the FITL approach are discussed, a special interest being dedicated to the synchronous digital hierarchy self-healing loop and the ATM over a passive optical network. We mention the main experiments and the standardization activities inherent to the domain     

Fixed broadband wireless access: state of the art, challenges, andfuture directions

This article provides an overview of fixed broadband wireless access technology. Focusing on the band below 3 GHz, we describe BWA service and carrier needs, deployment scenarios, architectural requirements, physical layer, medium access control, and radio link protocol requirements. We characterize fixed BWA channels, outline the major challenges of fixed BWA, and study requirements for future BWA systems. Finally, we show that the use of multiple antennas at both ends of a fixed wireless link provides significant leverages     

An overview of the Bluetooth wireless technology

The Bluetooth^TM wireless technology is designed as a short-range connectivity solution for personal, portable, and handheld electronic devices. Since May 1998 the Bluetooth SIG has steered the development of the technology through the development of an open industry specification, including both protocols and application scenarios, and a qualification program designed to assure end-user value for Bluetooth products. This article highlights the Bluetooth wireless technology     

An overview of local capacity in wireless networks

This article introduces a metric for performance evaluation of medium access schemes in wireless ad hoc networks known as local capacity. Although deriving the end-to-end capacity of wireless ad hoc networks is a difficult problem, the local capacity framework allows us to quantify the average information rate received by a receiver node randomly located in the network. In this article, the basic network model and analytical tools are first discussed and applied to a simple network to derive the local capacity of various medium access schemes. Our goal is to identify the most optimal scheme and also to see how does it compare with more practical medium access schemes. We analyzed grid pattern schemes where simultaneous transmitters are positioned in a regular grid pattern, ALOHA schemes where simultaneous transmitters are dispatched according to a uniform Poisson distribution and exclusion schemes where simultaneous transmitters are dispatched according to an exclusion rule such as node coloring and carrier sense schemes. Our analysis shows that local capacity is optimal when simultaneous transmitters are positioned in a grid pattern based on equilateral triangles and our results show that this optimal local capacity is at most double the local capacity of ALOHA based scheme. Our results also show that node coloring and carrier sense schemes approach the optimal local capacity by an almost negligible difference. At the end, we also discuss the shortcomings in our model as well as future research directions.     

Wideband local access: wireless LAN and wireless ATM

An overview of the status of wideband wireless local access technologies is provided. Service scenarios and availability of the market and products for wireless LAN and wireless ATM technologies are discussed. Similarities among IEEE 802.11 and HIPERLAN standards for wireless LANs and the developing prototypes for wireless ATM are evaluated. An update on the status of the available unlicensed bands in the United States as well as the status of the wideband wireless projects in the European Community and Japan are presented     

An overview of limited feedback in wireless communication systems

It is now well known that employing channel adaptive signaling in wireless communication systems can yield large improvements in almost any performance metric. Unfortunately, many kinds of channel adaptive techniques have been deemed impractical in the past because of the problem of obtaining channel knowledge at the transmitter. The transmitter in many systems (such as those using frequency division duplexing) can not leverage techniques such as training to obtain channel state information. Over the last few years, research has repeatedly shown that allowing the receiver to send a small number of information bits about the channel conditions to the transmitter can allow near optimal channel adaptation. These practical systems, which are commonly referred to as limited or finite-rate feedback systems, supply benefits nearly identical to unrealizable perfect transmitter channel knowledge systems when they are judiciously designed. In this tutorial, we provide a broad look at the field of limited feedback wireless communications. We review work in systems using various combinations of single antenna, multiple antenna, narrowband, broadband, single-user, and multiuser technology. We also provide a synopsis of the role of limited feedback in the standardization of next generation wireless systems.     

An overview of scheduling algorithms in wireless multimedia networks

Scheduling algorithms are important components in the provision of guaranteed quality of service parameters such as delay, delay jitter, packet loss rate, or throughput. The design of scheduling algorithms for mobile communication networks is especially challenging given the highly variable link error rates and capacities, and the. changing mobile station connectivity typically encountered in such networks. This article provides a survey of scheduling techniques for several types of wireless networks. Some of the challenges in designing such schedulers are first discussed. Desirable features and classifications of schedulers are then reviewed. This is followed by a discussion of several, scheduling algorithms which have been proposed for TDMA, CDMA, and multihop packet networks.     

Broadband wireless access

This article reviews the technologies and potential markets, applications, and architectures for broadband wireless access. The emergence of wireless communications for cellular systems is presented, together with its projected future evolution to mobile wideband systems. The field of broadband access systems, services, and network architectures is also covered, and then systems for broadband wireless communications for indoor local area networks and outdoor public fixed access networks are discussed. Broadband wireless access systems are emerging as a new and growing area of telecommunications, since the ability to provide access without extensive installation of copper or fiber infrastructures make wireless technology well suited for broadband services. Finally, some of the key enabling technologies, such as adaptive antennas and video compression, and the future architectural directions of broadband wireless networks are presented     

An assessment of alternative wireless access technologies for PCSapplications

The results of studies on three important wireless access technology issues in the personal communications services (PCS) arena are described. They are signal duplexing, multiplexing on the downlink, and channel frequency assignment. Each of these issues was addressed through the comparison of two competing technologies. In the area of duplexing, frequency division duplexing (FDD) was compared to time division duplexing (TDD) with the result that FDD is preferred if appropriate spectrum is available. Multiplexing on the downlink examined time division multiplexing (TDM) versus a burst downlink (TDMA). TDM is preferred for the wide-area local-exchange environment, but in certain indoor, office applications, TDMA may prove advantageous. The two methods of frequency channel assignment investigated are quasi-state autonomous frequency assignment (QSAFA) and dynamic channel assignment (DCA). QSFA is generally preferred, although indoor, multitenent environments with low port loading may benefit from the use of DCA. These analyses assume that the system uses time-division multiple access (TDMA)     

Fixed access network technologies

Telecommunications operators around the world are facing flat or declining revenues in their traditional services and expanding commercial and political demand for ubiquitous broadband access. This creates two opposing pressures — to cut costs radically and to invest heavily in new technology. The traditional fixed access network is central to both of these issues and this paper describes the technology that is being developed to meet these challenges.     

An overview of scheduling algorithms in MIMO-based fourth-generation wireless systems

In this article an overview of the scheduling algorithms proposed for fourth-generation multiuser wireless networks based on multiple-input multiple-output technology is presented. In MIMO systems a multi-user diversity gain can be extracted by tracking the channel fluctuations between each user and the base station, and scheduling transmission for the "best" user. Based on this idea, several opportunistic scheduling schemes that attempt to improve global capacity or satisfy users with different QoS requirements have been proposed. Transmit beamforming procedures aimed at increasing the channel fluctuations have been proposed. The simultaneous exploitation of both spatial and multi-user diversity is not straightforward; however, it may be achieved by a refined selection of the "best" user. In addition, a multiple access gain can be obtained from a simple SDMA/TOMA system. Finally, several resource allocation schemes are discussed for this hybrid multiple access system.     

LMDS宽带无线接入

LMDS系统在网络侧一般通过ATM或E1链路与骨干网相连，空中接口大多数采用基于ATM的信元结构进行无线传输；在用户端提供丰富的业务接口用于各类电信终端用户的接入，接口类型包括：POTS、ISDN业务；E1、部分E1、帧中继等租用线业务；10/100BaseT、ATM等突发数据业务，并可以增加其他网络设备，如VoIP网关提供分组电话业务等。鉴于LMDS丰富的业务类型，广泛应用于中小企业、宾馆酒店、高档写字楼、网络服务场所以及SOHO的综合业务接入；另外，对移动通信运营商而言，LMDS还可以用来实现移动基站与基站控制器的互联。与有线…