宽带CDMA无线接入系统及基站设计

宽带固定无线接入指的是从交换节点到固定用户终端部分或全部采用了无线方式.这里仅讨论对核心数据网络的接入.与有线接入比较,固定无线接入有如下显著特点:对自然条件适应性强.用户只要在覆盖区内,不需要特别定位和精确规划.在地形地物不适于架线铺缆的环境中,FWA系统显得尤其适合,建设速度快.     

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…     

Multicarrier DS-CDMA: a multiple access scheme for ubiquitous broadband wireless communications

We identify some of the key problems that may be encountered when designing a broadband multiple access system with bandwidth on the order of tens or even hundreds of megahertz. We commence with a comparative discussion in terms of the characteristics of three typical code-division multiple access schemes: single-carrier direct-sequence CDMA (SC DS-CDMA), multicarrier CDMA (MC-CDMA), and multicarrier DS-CDMA (MC DS-CDMA). Specifically, their benefits and deficiencies are analyzed when aiming to support ubiquitous communications over a variety of channels encountered in indoor, open rural, suburban, and urban environments. It is shown that when communicating in such diverse environments, both SC DS-CDMA and MC-CDMA exhibit certain limitations that are hard to circumvent. By contrast, when appropriately selecting the system parameters and using transmit diversity, MC DS-CDMA becomes capable of adapting to such diverse propagation environments at a reasonable detection complexity.     

A novel random wireless packet multiple access method using CDMA

Random packet CDMA, a novel packet-based multiple access scheme for connectionless, uncoordinated random channel access is proposed. Random packet CDMA, or RP-CDMA, utilizes a novel packet format which consists of a short header and a data portion. Each header is spread with a unique spreading code which is identical for all users and packets, while the data portion of each packet is spread by a randomly chosen spreading sequence. The receiver operates in two stages: header detection and data detection. For header detection a conventional spread spectrum receiver is sufficient. Headers are spread with a large enough processing gain to allow detection even in severe interference. The data portion is decoded with a sophisticated receiver, such as a multiuser detector, which allows for successful decoding of overlapping active packets. It is shown that the RP-CDMA system is detector capability limited and that it can significantly outperform spread ALOHA systems whose performance is limited by the channel collision mechanism. RP-CDMA also experiences a much smaller packet retransmission rate than conventional or spread ALOHA, and provides better spectral efficiencies.     

Designing a mobile broadband wireless access network

In this paper, a new OFDM-based air interface technology for a mobile broadband wireless system is described. The technology leverages the standard Internet protocol (IP) network elements to build the system and deploys a new air interface technology based on OFDMA. Cross-layer optimization played a major role in the design where the choices made in the physical, MAC, and link layers are also driven by the goal of extending the Internet to the wireless space. A major physical layer benefit of this air interface comes from the orthogonality property that the results in the elimination of in-cell interference are averaged and a worst-case interferer does not limit the system performance. The physical layer features not only result in high capacity but also provide very fine granularity of allocating air link resources, which improves the MAC and link-layer efficiency. The MAC and link layer provide contention-free, fast control channels between the RAR and the WTs. These channels are used to ferry a variety of signaling such as assignments of traffic channel, acknowledgements, channel quality, and traffic request reports. This holistic approach allows for a scheduler that could not only achieve high spectral efficiency but also allow for a fine control over QoS attributes such as latency, reliability, and service differentiation.     

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.     

OFCDM: a promising broadband wireless access technique

Future mobile communication systems aim to provide extremely high-speed data transmission, especially in the downlink. The broadband orthogonal frequency- and code-division multiplexing system with two-dimensional spreading (time and frequency domain spreading) is becoming a very promising technique for highspeed wireless communications due to its advantages over OFDM. This article presents the basic structure and main functions of the OFCDM system. A nonsequential code assignment scheme is introduced. The novel detection method for the OFCDM, called hybrid multi-code interference cancellation and minimum mean square error detection, is described. The application of advanced techniques to the OFCDM, such as turbo coding and MIMO, is also discussed. It is shown in this article that OFCDM is superior to OFDM.     

A multiple access scheme for wireless access to a broadband ATM LANbased on polling and sectored antennas

An adaptive polling scheme for multiple access in a broadband wireless local area networks (LANs) is proposed. It is designed to accommodate asynchronous transfer mode (ATM) traffic with a large and variable range of bit rates. The radio architecture is microcellular, with switched sectored-beam antennas and a small frequency reuse factor. Features of the multiple access scheme include polling rate depending on a terminal's average bit rate, fixed-length frames divided into segments corresponding to base antenna sectors, and automatic-repeat-request (ARQ) for error control, combined with randomized sector segment ordering. The steady-state performance (cell loss, call blocking and dropping probabilities, waiting time, and buffer occupancy) are evaluated by simulation for an open indoor environment, and for handoff, ARQ, and simple power control enhancements; focusing mainly on the effects of the propagation and interference conditions     

Space-time processing for broadband wireless access

We present an overview of research activities on space-time coding for broadband wireless transmission performed at AT&T Shannon Laboratory over the past two years. The emphasis is on physical layer modem algorithms such as channel estimation, equalization, and interference cancellation. However, we also discuss the impact of space-time coding gains at the physical layer on throughput at or above the networking layer. Furthermore, we describe a flexible graphical user interface attached to our physical layer simulation engine in order to explore the performance of space-time codes under a variety of practical transmission scenarios. Simulation results for the EDGE cellular system and the 802.11 wireless LAN environment are presented     

下一代宽带无线接入技术

在介绍IEEE802．16的发展的基础之上，着重阐述了其协议栈模型、物理层特性和MAC特性，并总结了它的优势所在。相信802．16技术作为下一代理想的宽带无线接入技术，一定能够解决目前仍然存在的技术和应用问题，构建出理想的下一代宽带无线接入网。     

Engineering wireless broadband access to IPTV

IPTV is now extending to wireless broadband access. If broadband video streaming is to achieve competitive quality the video stream itself must be carefully engineered to cope with challenging wireless channel conditions. This paper presents a scheme for doing this for H.264/AVC codec streaming across a WiMAX link. Packetization is an effective tool to govern error rates and, in the paper, source-coded data-partitioning serves to allocate smaller packets to more important data. A packetization strategy is insufficient in itself, as temporal error propagation should also be addressed by insertion of intra-coded data. It may be necessary to include redundant packets when channel conditions worsen. The whole should be protected by application-layer rateless coding. Therefore, the contribution of the paper is a complete scheme comprised of various protection measures aimed at robust IPTV streaming. Due to computational overheads, the scheme is aimed at the new generation of smartphones with GHz CPUs.     

Adaptive radio resource allocation for multiple traffic OFDMA broadband wireless access system

1 Introduction Next-generation wireless communication systems (systems beyond 3G) will be required to provide flexible and easy deployment solution to high-speed communications and to support a variety of services utilizing advanced multiple access techni…     

Antenna systems for broadband wireless access

Broadband wireless access along with evolving mobile Internet and multimedia services are driving the surge of research and development activities for future wireless communication systems. We provide an overview of antenna systems for broadband wireless communications and introduce some of the important issues surrounding them. The approach we use is to first provide a general framework of how antenna systems may be utilized in wireless communication systems and then describe the antenna systems themselves. In particular, we consider antenna systems for the base station, mobile station, and then finally multiple-input multiple-output antenna systems where antenna systems are utilized at both the base and mobile stations     

浅谈宽带无线接入技术的应用

0 引言 随着通信技术的飞速发展及社会生活水平的不断提高，传统的、纯粹的话音业务已经不能满足人们的需求，特别是随着互联网的迅猛发展，人们更希望享受到多媒体化、多样化、个性化的电信业务，数据业务量的猛增使人们对通信带宽的需求日益高涨。光纤接入虽然代表了未来宽带接入的方向，但其庞大的工程量和巨额的资金投入使其难以在近期一蹴而就。应运而生的宽带无线接入技术，以其建网的快速灵活和经济特性受到了广泛关注，新老运营商均对其表现出浓厚的兴趣。     

基于IEEE 802.16a的宽带无线接入系统

IEEE802.16a是固定宽带无线接入系统最新国际标准,基于该标准的宽带无线接入系统在无线传输方面具有调制方式动态选择的特点,可支持多业务;介绍的宽带无线接入系统具备IEEE802.16a建议的物理层、MAC子层、业务汇聚子层、及加密子层等实体,同时描述了一个实际的宽带无线接入系统必须具备的业务接口处理及系统管理等实体,并给出了各实体间的关系。     

Traffic characterization of a residential wireless Internet access

Traffic characterization is an important means for Internet Service Providers (ISPs) to adapt and to optimize their networks to the requirements of the customers. Most network measurements are performed in the backbone of these ISPs, showing both, residential and business Internet traffic. However, the traffic characteristics of business and home users differ significantly. Therefore, we have performed measurements of home users at a broadband wireless access service provider in order to reflect only home user traffic characteristics. In this paper, we present the results of these measurements, showing daily traffic fluctuations, flow statistics as well as application distributions. The results show a difference to backbone traffic characteristics. Furthermore, we observed a shift from web and Peer-to-Peer (P2P) file sharing traffic to streaming applications.     

IEEE 802.20: mobile broadband wireless access

This article provides a survey of the emerging IEEE 802.20 standard, also known as mobile broadband wireless access. It provides an introduction to the activities with regard to this standard, including purpose and scope that the specification defines. The relationship with other similar standards such as IEEE 802.16e and 3G are discussed as well. Various technical details of the standard are presented, including quality of service parameters, data rates available to end users, application support, and security. Characteristics that the air interface should provide, specifically in regard to the physical and medium access control layers, are detailed as well     

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     

Smart antennas for broadband wireless access networks

This article is an overview of smart antenna applications in fixed broadband wireless access networks. Different smart antenna techniques are described including advances such as “spatial multiplexing” that can dramatically increase the performance of BWA networks. The impact of SA techniques on capacity and throughput of BWA networks is discussed     

Performance analysis of a multiple access protocol for voice and data support in multiuser broadband wireless LANs

Wireless Local Area Networks (WLANs) is one of the most promising access technologies for the upcoming fourth-generation wireless communication systems. In the last few years, several research efforts have been devoted to investigate possible multiple access schemes capable of supporting real-time traffic as well as best-effort data transmissions. In particular, the use of suitable transmission schemes allows not only to achieve higher data-rates, but also to perform resource allocation in order to guarantee specific service requirements. In this paper we propose a medium access control (MAC) scheme for a WLAN supporting real-time (voice) and best-effort (data) services, based on Orthogonal Frequency Division Multiplexing (OFDM) technique. A suitable analytical approach is proposed in order to derive the performance of the proposed MAC scheme. In particular, it is shown in the paper that a high overall network capacity in terms of simultaneously active users is achieved by effectively exploiting the multiuser capabilities offered by OFDM, together with a proper service differentiation. Work partially supported by MIUR within the WOMEN project. Romano Fantacci, (M’87,SM’91, F’05) born in Pistoia, Italy, graduated from the Engineering School of the Universit di Firenze, Florence, Italy, with a degree in electronics in 1982. He received his Ph.D. degree in telecommunications in 1987. After joining the Dipartimento di Elettronica e Telecomunicazioni as an assistant professor, he was appointed associate professor in 1991 and full professor in 1999. His current research interests are digital communications, computer communications, queuing theory, satellite communication systems, wireless broadband communication networks, ad-hoc and sensor networks. He has been involved in several European Space Agency (ESA) and INTELSAT advanced research projects. He is the author of numerous articles published in prestigious communication science journals. He guest edited special issues in IEEE Journals and magazines and served as symposium chair of several IEEE conferences, including VTC, ICC and Globecom. Professor Fantacci received the IEE IERE Benefactor premium in 1990 and IEEE COMSOC Award Distinguished Contributions to Satellite Communications in 2002. He is currently serving as Editor for Telecommunication Systems, IEEE Trans. Commun. and IEEE Transactions on Wireless Communications. Gianluca Vannuccini born in Florence, Italy, graduated in Electronics Engineering in 1999. He received his Ph.D. degree in Telematics and Information Society in 2003 from the Electronics and Telecommunications Department of the University of Florence. During 2002 he was for six months in IBM Zurich Research Laboratory, Zurich, Switzerland, working in a research project on IEEE 802.11e performance evaluation. During the Ph.D. course, he has published on several IEEE conferences and served as reviewer for several journals on the telecommunications and telematics research area. He has been IEEE student member since 1999 and IEEE member since 2004. He is now with the IT department of the Florence local government organization, where he works as a program manager on data quality and integration and e-government IT projects. Gabriele Vestri was born in Florence (Italy) in November 1976. He received his degree in telecommunications from the Universit di Firenze, Florence, Italy, in March 2002. He has been research scientist for CSO Ophthalmic (Florence) since September 2002. His current research interests include ophthalmic instruments, contact lens design, image processing, the effects of optical aberrations and of retinal architecture of the eye on visual performance.