基于移动IP的组网方案探讨

下一代无线通信标准将能提供无缝、高QoS、高速率的基于IP的无线业务。IEEE802．16宽带无线接入技术WiMax的出现使得无线网络向4G过渡成为可能。WiMax技术将作为宽带无线接入应用。对比了WiMax和Wi-Fi的技术，提出一个融合Wi-Fi和WiMax的组网解决方案。     

基于WiMax的LDPC码性能研究

WiMax（全球微波互联接入）是一种基于IEEE 802.16标准的无线宽带接入城域网技术,它能提供面向互联网的高速连接,数据传输距离达50 km,具有QoS保障、传输速率高、业务丰富多样等优点。WiMax在信道编码方式中增加了LDPC（低密度奇偶校验）码。文中对WiMax中LDPC编码算法和译码算法进行了深入研究,用C语言实现了多种码长和码率的LDPC编译码仿真,其中编码采用IEEE 802.16e-2005提供的方法,译码采用BP（置信传播）译码算法。仿真结果显示WiMax的LDPC码具有优异的编译码性能。     

Design of the QoS framework for the IEEE 802.16 mesh networks

IEEE 802.16 (WiMax) technology is designed to support broadband speeds over wireless networks for the coming era of broadband wireless access (BWA). IEEE 802.16 is expected to provide transmission of high‐rate and high‐volume multimedia data streams for fixed and mobile applications. As an extension of point‐to‐multipoint (PMP) configuration, the IEEE 802.16 mesh mode provides a quicker and more flexible approach for network deployment. Multimedia networking requires quality‐of‐service (QoS) support, which demands elaborate mechanisms in addition to the four service types defined in the specification. By examining standard centralized and distributed scheduling/routing schemes in the mesh mode from QoS aspect, a BS‐controlled and delay‐sensitive scheduling/routing scheme is proposed in the paper. Associate mechanisms including admission control, flow setup and link state monitoring are also proposed. Integration of the proposed mechanisms is presented as a complete QoS framework. Simulation study has demonstrated that the average delay as well as the delay jitters per hop in the proposed scheme is smaller than that of the distributed scheme and much smaller than that of the centralized scheme. Furthermore, proposed mechanisms can also achieve higher throughput than the contrasts and generate much smaller signaling overhead, making the proposed framework a promising scheme for multimedia support in the IEEE 802.16 mesh network. Copyright © 2009 John Wiley & Sons, Ltd.     

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     

WiMax标准下3G技术在智能电网中的运用分析

智能电网要求实现信息的快速传递与高度共享,为达到此目的,研究了3G技术新标准——WiMax下的无线接入方法。首先,根据智能电网特性提出了智能电网基本通信体系架构;然后结合WiMax技术的特点提出了相应的WiMax电网通信方案,该方案通过无线接入方式以及分级分层管理模式可实现系统中信息的共享与即时传输,极大地提高了电网的信息化、互动化水平。最后对此项技术在电力系统中的运用进行了例证分析及前景展望,对可能存在的问题进行了分析与探讨。     

WiMax系统及其QoS机制研究

光纤技术的普遍应用使骨干网的承载能力大大提高，造成接入网成为业务的。瓶颈”。宽带无线接入系统WiMax具有带宽利用率高、覆盖范围大以及支持移动性等优点，是采用无线方式打破接入网。瓶颈。的重要一步。WiMax系统虽然给接入网增加了许多新的特性，但也带来了许多新问题，比如无线环境中的安全保证、动态资源管理、移动性管理等，特别是QoS机制，是复杂通信环境中提供可靠的端到端业务的重要保证。这些问题需要在实践中不断完善加以解决。     

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     

Feedback-based real-time streaming over WiMax

The IEEE 802.16 standard (commonly known as WiMax) has emerged as one of the strongest contenders for broadband wireless access technology. At the same time, with the steady growth of real-time services such as voice over IP and video on demand, supporting delay sensitive streaming data over WiMax is becoming crucial. In this article we use commonly used techniques such as forward error correction (FEC) and automatic repeat request (ARQ) to support streaming services over WiMax without violating what has already been standardized. In particular, we look at the flexible features provided by media access control (MAC) layer of WiMax and exploit them for providing better streaming performance. We use the channel state information to dynamically construct the MAC packet data units. The sizes of these units are thusly determined such that the packet dropping probability is minimized without compromising the goodput. The simulation results presented show the performance enhancements of the proposed ARQ-enabled adaptive algorithm for streaming data     

一种多频带印刷单极子天线的设计

提出了一种小型化的用于WLAN/WiMax通信系统的多频带印刷单极子天线。通过改进双“G”形的振子结构,使天线能在2.4 GHz,3.5 GHz和5.5 GHz谐振,实现2.4/5.2/5.8 GHz WLAN 和3.5/5.5 GHz WiMax频带的覆盖。对加工后的天线模型测试表明,天线在工作频带内具有较宽的阻抗带宽和较好的辐射特性。因此,该天线可以应用在多频带无线通信系统中。     

Where next for the handset? [multiple wireless services in single device]

There is a general belief that innovative wireless technologies are converging to meet a whole range of specific user demands, with new wireless standards transforming the capabilities of the ubiquitous mobile. This article examines some of the technologies which are going into the handset, which can then be seamlessly switched between. These include, wireless fidelity (Wi-Fi), UMTS (3G), GPRS (2.5G) or WiMax (IEEE 802.16d).     

无线宽带接入技术浅析

在无线数据通信系统中,宽带无线接入获得了广泛的关注,对于宽带无线接入技术的选择将会影响未来通信市场的走向。本文对比研究了WiMAX,Wi-Fi,LTE三种无线接入技术遵循的标准和优缺点,对以上三种无线接入技术进行总体性的比较研究,并对未来无线宽带接入技术的发展进行了展望。     

WiMax与3G LTE网络互联与融合技术研究

本文先分析WiMax与3GPP长期演进项目(LTE)两种无线接入技术融合的可能性.基于通用链路层(GLL)和协同无线资源管理(CRRM)机制的引入.提出了两种不同的协作程度的百联融合技术的网络架构.引入GLL的目的是为不同的无线接入机制提供统-的链路层数据处理.同时带来两个新的研究子课题:异构发送分集与异构多跳技术.CRRM完成网络间无线资源的协调管理,以达到最优化无线资源利用率和最大化系统容量的目的.几种关键的协同无线资源管理机制包括:接人选择、负载均衡、动态频谱控制技术在文中进行了详细分析及讨论.     

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     

宽带无线接入系统的网络架构发展

本文介绍了宽带无线接入系统网络架构的发展背景和目标,并分析了不同宽带无线接入系统网络架构发展状况和技术特点以及进一步发展演进的方向.     

Delay constrained uplink scheduling policy for rtPS/ertPS service in IEEE 802.16e BWA systems

WiMAX is a promising broadband wireless networking technology and is expected to take the place of broadband access solutions such as DSL and cable. Owing to its superior support in mobility, it is expected to provide integrated voice and data service to realize broadband mobile computing. In order to reach better quality‐of‐service (QoS) requirements for real‐time applications, the IEEE 802.16e standard defines five different services among traffic categories with different multimedia requirements. However, the problem of choosing the right set of medium access control parameters and packet scheduling policy to provide strict QoS guaranteed in IEEE 802.16e Broadband Wireless Access (BWA) systems remains unsolved and left as an open issue. In this paper, we propose a novel polling‐based uplink packet scheduling policy for real‐time Polling Service and extended real‐time Polling Service (rtPS/ertPS) traffic to support real‐time applications, with strict delay requirements, such as variable bit rate (VBR) traffic in IEEE 802.16e BWA systems. The proposed transmit‐permission policy can derive sufficient conditions such that all the rtPS/ertPS sources satisfy their time constraints to provide deterministic QoS guarantees. In addition to theoretical analysis, simulations are conducted to evaluate the performance of the proposed scheme. As it turns out, our design provides a good quality performance in the IEEE 802.16e BWA systems. Copyright © 2008 John Wiley & Sons, Ltd.     

COFDM技术在无线视频传输中的应用

编码正交频分复用（Coded orthogonal frequency division multiplexing, COFDM）是一种多载波数字通信调制技术,它具有频谱利用率高和可对抗多径时延扩展等特点。文章介绍了COFDM技术的基本原理,对基于该技术的无线视频传输系统在海上视频传输的实际应用进行了分析论述。     

Wi-Fi based broadband wireless access for users on the road

This paper considers the provision of broadband wireless access (BWA) for users on the road. A Wi-Fi based system, which utilises a three-tier network architecture, is suggested as a readily available way of achieving BWA for road vehicles. However, the use of this approach and technology still poses a number of specific challenges. We identify and examine in greater depth a number of the challenges, and propose possible solutions to overcome them.     

MIMO systems for broadband wireless communications

The emergence of broadband wireless access (BWA) and mobility poses significant challenges to the future telecommunications landscape. Multiple input multiple output (MIMO) is a potential technology that can be used to improve system performances such as coverage, capacity and data rates for broadband wireless networks. Although this technology has proved to be beneficial for both current and future services by many research results, it is not clear how these benefits can be practically achieved with a MIMO system. Fundamental issues on capacity enhancement and performance limits need to be addressed before operators will be willing to deploy MIMO systems in their networks. This paper addresses some of the key issues that remain open regarding MIMO technology for BWA. The paper focuses on MIMO channel modelling and capacity analysis.     

Optimal Radio Resource Partition for Joint Contention- and Connection-Oriented Multichannel Access in OFDMA Systems

The IEEE 802.16e world interoperability for microwave access (WiMax) system plays an important role in the future wireless metropolitan area network (WMAN). Orthogonal frequency division multiple access (OFDMA), adopted in the IEEE 802.16 e WiMax system, has many advantages in the physical layer, but also poses many challenges for radio resource allocation. One of interesting radio resource allocation issue in the OFDMA system is to partition the overall radio resource (bandwidth and time duration) into two portions: one for random access and the other for connection-oriented access. In the IEEE 802.16 e WiMax system, a truncated binary backoff algorithm is adopted to resolve the contention in random access, while the time-division OFDMA is used for the connection-oriented access. The main contribution of this paper is to design an analytical approach to determine the optimal amount of reserved radio resource in both time and frequency domains for random access, with the objective of maximizing the overall efficiency of radio resource while satisfying the delay requirements for supporting real-time services. Furthermore, an analytical model for calculating the access latency and the efficiency of the reserved radio resources is developed.     

The IEEE 802.16 Working Group on broadband wireless

This article describes the new initiative on broadband wireless access (BWA) that has formed Working Group 802.16 in the IEEE 802 LAN/MAN Standards Committee. The aim is to provide the reader with highlights of the IEEE 802 activities in order to enable better dissemination of these standards into marketable products as well as seek new ideas to be brought into the IEEE 802 arena. BWA systems, utilizing base stations to provide broadband data to business or homes, offer an alternative to wired “last-mile” access links using fiber, cable, or telephone lines. As illustrated, the base stations may be either terrestrial, in orbit, or mounted on airplanes or dirigibles in the stratosphere. The customer terminals can carry two-way communications for Internet access, digital video, telephony, and other services