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     

Distributed wireless communication system: a new architecture for future public wireless access

The distributed wireless communication system (DWCS) is a new architecture for a wireless access system with distributed antennas, distributed processors, and distributed control. With distributed antennas, the system capacity can be expanded through dense frequency reuse, and the transmission power can be greatly decreased. With distributed processors control, the system works like a software or network radio, so different standards can coexist, and the system capacity can be increased by coprocessing of signals to and from multiple antennas.     

宽带无线接入技术发展展望

根据目前的技术标准和将来的发展，主流的宽带无线接入技术可以分为：* 无线个域网(Wireless PersonalArea Networks, WPAN)技术，如蓝牙技术(Bluetooth)和IEEE 802.15;* 无线局域网(Wireless LANs,WLAN)技术，如IEEE 802.11b/a和ETSI HIPERLAN/2;* 固定宽带无线接入技术(FBWA)，如IEEE 802.16无线城域网(WMAN)技术。虽然宽带无线接入技术的标准化历史不长，但发展却非常迅速，在无线通信领域的地位越来越重要。因此，分析各种宽带无线接入技术的特点、应用前景和发展趋势具有非常重要的意义。无线局域网技术开发无线局…     

Broadband wireless access with WiMax/802.16: current performance benchmarks and future potential

The IEEE 802.16 family of standards and its associated industry consortium, WiMax, promise to deliver high data rates over large areas to a large number of users in the near future. This exciting addition to current broadband options such as DSL, cable, and WiFi promises to rapidly provide broadband access to locations in the world's rural and developing areas where broadband is currently unavailable, as well as competing for urban market share. WiMax's competitiveness in the marketplace largely depends on the actual data rates and ranges that are achieved, but this has been difficult to judge due to the large number of possible options and competing marketing claims. This article first provides a tutorial overview of 802.16. Then, based on extensive recent studies, this article presents the realistic attainable throughput and performance of expected WiMax compatible systems based on the 802.16d standard approved in June 2004 (now named 802.16-2004). We also suggest future enhancements to the standard that could at least quadruple the achievable data rate, while also increasing the robustness and coverage, with only moderate complexity increases     

面向未来无线通信系统的小蜂窝网络综述

为了满足人们日益增长的数据流量需求,未来无线通信系统将向更小的小区部署迁移.小蜂窝网络是下一代无线通信系统的关键技术,也是适应未来更加复杂通信环境的有效途径.首先介绍了小蜂窝网络的基本概念,论述了其主要的技术特点和独特的应用优势,分析了其在未来无线通信系统中与其他各种技术可能的融合场景并讨论了对应的特点和存在的难题;然...     

我国宽带无线接入应用前景广阔

宽带无线接入加快我国信息化过程宽带无线接入系统可以加快我国信息化进程,而且可以节省资金,解决现在的电信网解决不了的一些问题.作为个人用户用到56K或许就足够了,但是宽带接入主要用于大的企业、集团用户、小区或者政府机关,这些部门需要一个总的宽带出口.没有这个宽带出口,内部的计算机就联不起来,上不了互联网,而且一个一个上网费用也昂贵.……     

宽带无线通信的现状和展望

目前第二代移动通信系统的主要制式有ＧＳＭ、ＴＤＭＡ（Ｄ－ＡＭＰＳ）、ＰＤＣ、ｃｄｍａＯｎｅ等,它们提供的主要是语音业务。日本１９９８年引入了ｉ－Ｍｏｄｅ移动数据业务后,欧洲和中国也部署了２．５Ｇ的基于ＧＰＲＳ的数据业务,北美和韩国则是采用基于ｃｄｍａＯｎｅ的无线数据业务。 全球移动通信发展的速度非常迅速,１９９９年已经超过４亿用户。按照最新的估计,全球达到１０亿用户的记录将会在２００２年上半年载入史册。全球上网手机的数量超过ＰＣ机上网数量的时间将提前到２００２年。据预测,在２０００年,具有上网功…     

七大趋势勾勒美好明天--宽带无线接入技术发展及展望

全球通信发展的宽带化、无线化、个人化、分组化是大势所趋.同有线接入系统一样,无线接入系统经历了由窄带到宽带,由面向话音业务到面向数据、多媒体业务的转变.随着数据业务在电信总业务中的比例不断扩大,特别是随着Internet技术的迅猛发展,现有的有线接入系统远远不能满足人们的宽带业务需求;另一方面随着电信市场的不断开放,新运营商不断加入,形成了多方竞争的局面.运营商面临的问题是,采用何种技术才能快速而低成本地向用户快速、廉价地提供高质量的宽带电信业务.在这种背景下,宽带无线接入应运而生.     

Broadband wireless access solutions based on OFDM access in IEEE802.16

Broadband wireless access is the most challenging segment of the wireless revolution since it has to demonstrate a viable alternative to the cable modem and DSL technologies that are strongly entrenched in the last mile access environment. The Analysis, Research, and Consultancy (ARC) Group forecasts that the fixed wireless deployments in both homes and businesses will reach almost 28 million by 2005, with North America and Western Europe accounting for 24 percent and 27 percent of these, respectively. Whether the promise of BWA will materialize depends on its appeal to telecom operators from the perspective of deployment economics, where the critical factor is the ease of installation of broadband wireless subscriber units. This ultimately leads to nonprofessional installation of integrated all-indoor BWSUs. Consequently the physical layer (PHY) has to mitigate the very tough impairments that characterize these non-line-of-sight environments. In this context we overview the work of the one of the IEEE 802.16 standard subcommittee projects that deals with a BWA solution based on OFDM access (OFDMA) aiming at the most challenging NLOS scenarios     

Cooperative communication in wireless networks

Transmit diversity generally requires more than one antenna at the transmitter. However, many wireless devices are limited by size or hardware complexity to one antenna. Recently, a new class of methods called cooperative communication has been proposed that enables single-antenna mobiles in a multi-user environment to share their antennas and generate a virtual multiple-antenna transmitter that allows them to achieve transmit diversity. This article presents an overview of the developments in this burgeoning field.     

Multiple access in wireless digital networks

General principles for the design of a multiple-access system for large numbers of terminals transmitting to a single hub station are discussed. The importance of understanding the nature of the traffic to be carried by the network is emphasized. After some discussion of multiple access options for steady traffic and for slowly varying traffic, the use of random-access protocols for rapidly varying traffic is explained. Two general random-access protocols have been used in a variety of data networks, ALOHA and CDMA. Although these two techniques have different origins and are generally thought of as separate, they are in fact but different ways of looking at the same basic signals. The author shows that the use of multiple spreading codes in a CDMA network is not necessary in order to achieve multiple access capability. A single code can greatly reduce the complexity of a CDMA system. He introduces a spread-spectrum version of an ALOHA channel (spread ALOHA) which is equivalent to a CDMA channel with a common spreading code for all users. The equivalence the author demonstrates opens the door to a variety of techniques commonly used in ALOHA channels which can significantly increase both the throughput and the efficiency of the spread-spectrum channel     

Broadband access in Korea: experience and future perspective

With the growing popularity of the Internet, Korea has been successful in providing broadband Internet services to the level of universal service. More than 70 percent of households have high-speed Internet connection, and their lives have been changed dramatically. The cutting edge technology of broadband Internet has a profound impact on many aspects of the economy, education, entertainment, and social culture. This article addresses the experiences and future perspectives of KT (formerly Korea Telecom) in providing the broadband network and services in Korea. We present our experiences in the deployment of the world's largest ADSL network, and our ongoing deployment of VDSL and WLAN. Based on the accomplishment in broadband access, we also provide a forecast on the next generation of broadband services and the corresponding technologies required to support these services.     

Cache access and replacement for future wireless Internet

In the last two decades we have witnessed the tremendous success of the Internet and its technologies. Wireless Internet access becomes important to continue this success. However, wireless Internet access suffers from limited battery power, limited bandwidth, high mobility, and an increasing degree of heterogeneity. Cache mechanisms have been proposed to improve access latency, reduce battery power consumption, and reduce bandwidth usage in the wireless Internet. In this article we discuss issues in wireless Internet caching. In particular, we classify and survey cache access mechanisms and replacement algorithms, which should be designed considering both the limitations of wireless networks/devices and heterogeneity of the future wireless Internet.     

Quantum communication for wireless wide-area networks

In this paper, a quantum routing mechanism is proposed to teleport a quantum state from one quantum device to another wirelessly even though these two devices do not share EPR pairs mutually. This results in the proposed quantum routing mechanism that can be used to construct the quantum wireless networks. In terms of time complexity, the proposed mechanism transports a quantum bit in time almost the same as the quantum teleportation does regardless of the number of hops between the source and destination. From this point of view, the quantum routing mechanism is close to optimal in data transmission time. In addition, in order to realize the wireless communication in the quantum domain, a hierarchical network architecture and its corresponding communication protocol are developed. Based on these network components, a scalable quantum wireless communication can be achieved.     

Traffic models for wireless communication networks

Introduces a deterministic fluid model and two stochastic traffic models for wireless networks. The setting is a highway with multiple entrances and exits. Vehicles are classified as calling or noncalling, depending upon whether or not they have calls in progress. The main interest is in the calling vehicles; but noncalling vehicles are important because they can become calling vehicles if they initiate (place or receive) a call. The deterministic model ignores the behavior of individual vehicles and treats them as a continuous fluid, whereas the stochastic traffic models consider the random behavior of each vehicle. However, all three models use the same two coupled partial differential equations (PDEs) or ordinary differential equations (ODEs) to describe the evolution of the system. The call density and call handoff rate (or their expected values in the stochastic models) are readily computable by solving these equations. Since no capacity constraints are imposed in the models, these computed quantities can be regarded as offered traffic loads. The models complement each other, because the fluid model can be extended to include additional features such as capacity constraints and the interdependence between velocity and vehicular density, while the stochastic traffic model can provide probability distributions. Numerical examples are presented to illustrate how the models can be used to investigate various aspects of time and space dynamics in wireless networks     

Multimedia communication in wireless sensor networks

The technological advances in Micro ElectroMechanical Systems (Mems) and wireless communications have enabled the realization of wireless sensor networks (Wsn) comprised of large number of low-cost, low-power, multifunctional sensor nodes. These tiny sensor nodes communicate in short distances and collaboratively work toward fulfilling the application specific objectives ofWsn. However, realization of wide range of envisionedWsn applications necessitates effective communication protocols which can address the unique challenges posed by theWsn paradigm. Since many of these envisioned applications may also involve in collecting information in the form of multimedia such as audio, image, and video; additional challenges due to the unique requirements of multimedia delivery overWsn, e.g., diverse reliability requirements, time constraints, high bandwidth demands, must be addressed as well. Thus far, vast majority of the research efforts has been focused on addressing the problems of conventional data communication inWsn. Therefore, there exists an urgent need for research on the problems of multimedia communication inWsn. In this paper, a survey of the research challenges and the current status of the literature on the multimedia communication inWsn is presented. More specifically, the multimediaWsn applications, factors influencing multimedia delivery overWsn, currently proposed solutions in application, transport, and network layers, are pointed out along with their shortcomings and open research issues.