HiperLAN／2下一代的无线局域网技术

HPERLAN/2是欧洲ETSI为了满足未来的Internet访问和宽带多媒体数据业务的需求，开发的新一代的WLAN技术标准，它在5GHA的频段上运行，它采用OFDM作为物理层，因而可以有效地对抗多径干扰，提高数据速率。另外由于采用和802.11a相同的物理层，因此它们可以共享一些相同的部件，从而在较大的范围内降低系统成本，本对HiperLAN/2的特点和协议栈结构作了简单介绍。     

高速率无线个人域网(WPAN)

未来的无线通信系统大到覆盖全球的卫星网，小到个人域网。高速无线个人域网（WPAN）工作在不需许可证2.4GHz频段，最高速率可达55Mbit/s。本文阐述了WPAN的基本概念、目标应用以及媒体接入控制（MAC）层与物理层（PHY）的标准情况，还与无线局域网（WLAN）进行了比较。     

干扰受限环境下蓝芽系统的性能及自适应跳频共存机制

随着无线局域网(WLAN)的日益普及和无线个人局域网(WPAN)的飞速发展，由于共享同一频段而产生的系统间干扰不可避免。本文着重讨论基于IEEE802．1lb标准的WLAN对基于蓝芽(Bluetooth)的短距离无线通信系统的影响。在利用MATLAB和C 搭建的系统干扰模型的仿真平台上，实现了基于蓝芽物理层的自适应跳频(Adaptive Frequency Hopping-AFH)共存机制(Co—existence Mechanism)。仿真结果显示，通过简单的AFH信道选择模块，可以有效减轻WLAN对蓝芽的干扰影响。     

HiperLAN/2下一代的无线局域网技术

HiperLAN/2是欧洲ETSI为了满足未来的Internet访问和宽带多媒体数据业务的需求,开发的新一代的WLAN技术标准,它在5GHz的频段上运行,它采用OFDM作为物理层,因而可以有效对抗多径干扰,提高数据速率。另外由于采用和802.11a相同的物理层,因此它们可以共享一些相同的部件,从而在较大的范围内降低系统成本。对HiperLAN/2的特点和协议栈结构作了简单介绍。     

IEEE802．11无线局域网及其最新发展

无线局域网WLAN(Wireless Local Area Networks)是20世纪90年代计算机与无线通信技术相结合的产物,它使用无线信道来接入网络,为通信的移动化、个人化和多媒体应用提供了潜在的手段,并成为宽带接入的有效手段之一。802.11标准定义了单一的MAC层和多样的物理层,其物理层标准主要有802.11b/a/g。     

HiperLAN/2下一代的无线局域网技术

HiperLAN／2是欧洲ETSI为了满足未来的Internet访问和宽带多媒体数据业务的需求，开发新一代的WLAN技术标准，它在5CHz的频段上运行，它采用OFDM作为物理层，因而可以有效对抗多径干扰，提高数据速率。另外由于采用和802．11a相同的物理层，因此它们可以共享一些相同的部件，从而在较大的范围内降低系统成本。对HiperLAN／2的特点和协议栈结构作了简单介绍。     

无线局域网通信安全机制研究

随着无线局域网（WLAN）应用规模不断扩大,其通信安全问题备受业界关注。通过分析现有的WLAN在物理层、数据链路层和网络层三个层次的安全机制,从访问控制和数据加密两个方面指出了其局限性和缺陷,提出了运用隔离技术、升级加密方案和VPN技术等措施构建多层次的安全体系,确保WLAN通信安全。     

几种IEEE802.11无线局域网协议的比较

WLAN的出现，充分解决了有线网络先天性缺陷所带来的一系列问题。与有线网络相比，WLAN具备了很多特定优势。作为有线局域网的一种补充和扩展，WALN使计算机具有了可移动性，能快速、方便地解决有线网络不易实现的网络连通问题，成为今后网络发展的主导方向。IEEE802．11标准是IEEE制定的无线局域网标准，各厂商的产品在同一物理层上可以互相操作，这样就使得无线局域网的两种主要用途“多点接入”和“多网段互联”更易于低成本实现，从而为无线局域网的进一步普及打通了道路，文中介绍了几个常用标准的特点。     

WLAN网管系统的现状和发展

2001年以来，全球WLAN（无线局域网）市场应用的瓶颈被打破，中国也迎来了WLAN商业化运作和服务的春天，WLAN为我们带来了一种全新的、灵活的工作方式，同时也带来了新的挑战，本文将对WLAN网络管理的主要内容和具体指标进行阐述，并对各大厂商的WLAN网管产品进行简单介绍和比较。     

基于IEEE 802.11协议的WLAN无线资源管理浅析

本文研究了WLAN(无线局域网)中的无线资源管理问题.首先基于MAC分离的思想给出了一种新的WLAN框架结构,然后在此框架结构的基础上,分析了信道分配、功率控制以及负载均衡等无线资源管理问题,提出了相应的解决方案.在WLAN中引入无线资源管理技术,可以大幅度地提高WLAN的性能和容量.     

下一代无线局域网标准--HiperLAN/2

文章介绍了HiperLAN/2这一无线局域网标准,列举了基于HiperLAN/2的网络的特点,详细描述了HiperLAN/2的协议栈结构,最后给出了基于HiperLAN/2的无线网络的功能。     

A New Air Interface Concept for Wireless Multimedia Communications beyond the 3rd Generation

This paper presents a new air interface concept for wireless multimedia communications beyond the 3rd generation. The proposed air interface uses the same physical layer as that ofETSI HiperLAN/2 and IEEE 802.11a supporting transmission rate up to 54 Mb/sto form a W-CHAMB (Wireless CHannel-oriented Ad-hoc Multihop Broadband)network. Unlike HiperLAN/2, that is based on a central control, W-CHAMB is a self-organizing network without any central control. The responsibilities of organizing andcontrolling of W-CHAMB are fully distributed among wireless stations themselves.A channel-oriented MAC protocol that is based on the dynamic channel reservation (DCR) is proposed for W-CHAMB.Energy signals (E-signals) are used to realize distributed access priorities of wireless stations, to solve the hidden station problemand to achieve a MAC level acknowledgment (ACK) for a fast ARQ.The multihop traffic performance of IEEE 802.11a and W-CHAMB is intensively evaluated stochastically based on a prototypical implementation of the protocols. The superiority of the multihop traffic performance withW-CHAMB can be seen in comparison withIEEE 802.11a.     

HiperLAN2: broadband wireless communications at 5 GHz

Solutions for high data rates and local coverage have been developed over a couple of years in the area of wireless local area networking. The quality of service, security, mobility, and high throughput are key components that drive the standards for broadband wireless multimedia communications presently being developed in Europe as well as in the United States and Japan for the 5 GHz band. These technologies are well suited to complement third-generation cellular networks. HiperLAN type 2 (HiperLAN2) is one of these systems, which is being specified by the ETSI project BRAN. The core parts of the specification were finalized at the end of 1999. Almost total harmonization has been achieved between the standardization bodies in Europe and Japan (ETSI and ARIB, respectively). HiperLAN2 will provide data rates up to 54 Mb/s, and is intended for local communications in indoor and outdoor environments. An overview of the HiperLAN2 standard is presented together with exemplary link and system performance results     

一种适用于宽带无线IP网络的分组调度算法

自适应调制技术在许多新型的无线分组网络如WCDMA HSDPA、HiperLAN/2中得到广泛采用.本文在充分考虑自适应调制系统链路带宽随时隙呈不平均分布特点的基础上,提出一种全新的调度算法,自适应区分补偿公平队列(ADCFQ).该算法采用了基于工作量的分析方法,设计了不同功能的多个子队列,可以为系统所有待发流提供基本的QoS保证,为各个流公平共享剩余带宽,并能够通过合理的补偿机制克服无线环境中突发错误影响.分析和仿真结果表明,这一算法可以满足目标要求.此外,仿真中,针对自适应链路的特点,本文还提出了一种基于多状态Markov链的信道建模方法.     

HiperLAN 5.4-GHz low-power CMOS synchronous oscillator

A 5.4-GHz 0.25-μm very-large-scale-integration CMOS synchronous oscillator (SO) is proposed in this paper, which is designed to act as a local oscillator for HiperLAN systems. The advantage of using such an oscillator in a double-loop frequency synthesizer is demonstrated. The design strategy leading to an optimized SO with regards to its synchronization range is described. A test chip is presented, which provides a 150-MHz synchronization range and a -97-dBc/Hz phase noise at 10-kHz offset from the 5-GHz carrier, while consuming only 5 mA from a 2.5-V supply     

An OFDM-TDMA/SA MAC Protocol with QoS Constraints for Broadband Wireless LANs

Orthogonal frequency division multiplexing (OFDM) is an important technique to support high speed transmission of broadband traffic in wireless networks, especially broadband wireless local area networks (LANs). Based on OFDM, a new multiple access scheme, called OFDM-TDMA with subcarrier allocation (OFDM-TDMA/SA), is proposed in this paper. It provides more flexibility in resource allocation than other multiple access schemes such as OFDM-TDMA, OFDM-frequency division multiple access (OFDM-FDMA), and orthogonal frequency division multiple access (OFDMA). With OFDM-TDMA/SA, a medium access control (MAC) is designed for broadband wireless LANs. It optimizes bit allocation in subcarriers so that maximum bits are transmitted in each OFDM symbol under a frequency selective fading environment. The OFDM-TDMA/SA MAC protocol also supports three classes of traffic such as guaranteed, controlled-load, and best effort services. Based on the optimum subcarrier bit-allocation algorithm and considering heterogeneous QoS constraints of multimedia traffic, a hierarchical scheduling scheme is proposed to determine the subcarriers and time slots in which a mobile terminal can transmit packets. In such a way, the OFDM-TDMA/SA MAC protocol significantly increases system throughput in a frequency selective fading environment and guarantees QoS of multimedia traffic. Computer simulation is carried out to evaluate the performance of the OFDM-TDMA/SA MAC protocol. Results show that the new MAC protocol outperforms other MAC protocols for OFDM-based wireless LANs. This work was supported by the State of Georgia Yamacraw Project (E21-105).     

Adaptive random access and resource allocation scheme based on traffic load in HiperLAN type2 system

The MAC protocol of HiperLAN type2 is based on TDMA/TDD and provides access control and resource allocation schemes. We propose a scheme that provides adaptive random access and efficient resource allocation according to the traffic load for HiperLAN type2, by using access probability. The analysis and simulation results show that the proposed scheme performs better than the conventional scheme and supports priority services easily.     

HiperLAN/2与GPRS/UMTS网络的互联--全新的高速广域无线接入业务模式

本在介绍无线局域网HiperLAN／2标准及GPRS／UMTS网络的体系结构的基础上，对HiperLAN／2与GPRS／UMTS网络的互联进行了讨论。有两种不同的互联方式：紧耦合互联方式和松耦合互联方式，由于松耦合互联方式对GPRS／UMTS网络的影响最小，本重点对其安全性、移动性和QoS问题进行了讨论。