HIPERLAN/2与IEEE802.11a物理层比较

目前,支持宽带多媒体通信的无线局域网(WLAN)正在发展和标准化,其中两个标准是由ESTI BRAN定义的HIPERLAN／2和由IEEE定义的802.11a。它们都可以提供54Mbps的数据速率。其主要不同在于它们的媒体控制层(MAC)层,很多文章都时此进行了详细介绍。对两个标准的物理层进行比较,得出它们的异同之处。     

802.11p物理层OFDM基带调制器的FPGA实现

基于IEEE 802.11p标准的车辆无线通信系统作为智能交通系统的一部分,能极大地改善交通系统的安全性、有效性和实时性。该文详细描述了作者对车辆无线通讯系统关键技术进行的相关研究内容,并且在CycloneⅢEP3C120F平台上实现了一种基于IEEE 802.11p标准的物理层OFDM基带调制系统,效果理想,有很好的移植性。     

IEEE802.11ah物理层仿真平台与链路性能评估

通过对正在制定的IEEE802.11ah标准物理层进行理论调研,借助MATLAB软件搭建物理层仿真平台,并从传输误码率测试和链路预算等多角度对链路性能进行评估,验证了该技术在无线传感网、智能电网、仪器仪表等特种行业中的应用前景.     

无线局域网标准802.11b与802.11a的物理层比较

无线局域网(WLAN)已经存在10多年了,但由于原来一直把它单纯定位于有线LAN的延伸,加上无统一标准以及传输速率低,其应用难以推广.到上世纪末,随着自身技术的进步和标准的统一,WLAN被重新定位作为因特网高速无线接入技术,之后便开始被广泛应用于办公室、机场、酒店、商场、咖啡屋等公共热点场所(hotspots).因此,2000年WLAN被评为美国通信技术十大发展趋势之一.     

Efficient encoding of IEEE 802.11n LDPC codes

Addressed is the issue of LDPC coding for the emerging IEEE 802.11n standard. An efficient encoding algorithm is proposed. The algorithm is simple and easy to implement. The memory requirement is trivial     

一种基于IEEE802.11标准的SoftMAC实现方法

文章介绍IEEE802．11 MAC层的基本功能和MAC层实现的软硬件划分，对softMAC的单元模块、工作原理和验证过程进行了详细的说明。     

基于IEEE 802.11标准的WLAN的物理层方案

作为WLAN第一个成熟的标准，IEEE 802．11成功地解决了无线介质给WLAN造成的困难。本文详细地分析了WLAN在物理层上存在的困难，并给出了IEEE 802．11相应的解决方案。     

An Efficient Cross Layer Routing Protocol for Safety Message Dissemination in VANETS with Reduced Routing Cost and Delay Using IEEE 802.11p

Wireless Personal Communications - For successful message dissemination in urban vehicular ad hoc networks (VANETs) with reduced route cost and delay is challenging task due to high mobility of the...     

IEEE802.11协议中关联业务的实现

本文着重分绍了802.11协议中关联/再关联的定义,以及关联业务的实现和实现所采用的工具库ACE.     

Efficient IEEE 802.11 handoff based on a novel geographical fingerprint scheme

The effective coverage distance of wireless LAN (WLAN) being small, users may leave the coverage area of the specific access point (AP) from time to time while roaming. However, the wireless network is a shared medium. The air is open for everyone. In general there is collision if a few users attempt to transmit with the same channel that is more rigorous during handoff period because of active scan mode. The active scan will perform requests for searching available AP. Unfortunately, this function consumes too much resource in wireless communication, and also affect total performance. We will propose an advanced active scan to improve it. In our proposal, we convert RF signal distribution to a simple classification problem, like as XOR classifier with artificial neural network (ANN). We combine ANN with active scan to achieve our goal. And the weight, which trained by ANN presents the connection character of geography. Moreover, the weight could be stored in AP for reusing and is called geographical fingerprint. The average enhancement of reducing the active scan area is about 62%. Copyright © 2006 John Wiley & Sons, Ltd.     

IEEE802.11a的OFDM基带调制的FPGA实现

针对802.11无线局域网设计当中OFDM调制端基带部分的成形,提出了FPGA的具体实现方法。在数据的突发方式和连续方式下采取基于流量控制的缓冲机制,并在导频插入以及频谱安排的实现上采用FIFO加RAM的方式,对于PLCP前导训练序列直接从ROM中查表截入。采用BPSK和16QAM两种调制方式,设计中在一定程度上采用争取硬件资源换取延迟的做法。经验证,系统的频谱结构以及时域帧结构都满足设计要求,并且时延较小。     

An Efficient IEEE 802.11 ESS Mesh Network Supporting Quality-of-Service

IEEE 802.11 infrastructure basic service set (BSS) wireless local area networks (WLANs) are widely used, each comprising an access point (AP) and its associated stations. There is a need to interconnect BSSs wirelessly to create an extended service set (ESS) mesh network. We propose a solution for the architecture and protocols of a mesh distributed coordination function (MDCF) to interconnect a large number of APs in order to form an efficient ESS mesh network under distributed control. MDCF applies time-division multiple access to share the radio medium and is able to run on a single frequency channel on top of the IEEE 802.11a/b/g physical layers, concurrently to legacy stations. MDCF is capable to efficiently exploit channel capacity, fairly distribute bandwidth among the mesh points and support multihop relaying of a large number of concurrent traffic flows strictly observing specific quality-of-service requirements. Example simulation results proof the outstanding performance of the new concept proposed     

Enhancing IEEE 802.11p/WAVE to provide infotainment applications in VANETs

IEEE 802.11p/WAVE (Wireless Access for Vehicular Environment) is the emerging standard to enable wireless access in the vehicular environment. Most of the research contributions in this area has focused on safety-related applications, while comfort and information/entertainment applications (such as on board Internet access, point-of-interest notification, e-map download) have been considered only recently. Notwithstanding, the user interest in this kind of applications is expected to become a big market driver in a near future. In this paper, an extension to IEEE 802.11p is proposed that is compliant with the multi-channel operation of the WAVE architecture and targets at the support of non-safety applications, while preserving the delivery of safety services. The proposed W-HCF (WAVE-based Hybrid Coordination Function) protocol leverages controlled access capabilities on top of the basic contention-based access of the IEEE 802.11p; it exploits vehicles’ position information and coordination among WAVE providers in order to improve performances of delay-constrained and loss-sensitive non-safety applications.     

Efficient multi-Gb/s multi-mode LDPC decoder architecture for IEEE 802.11ad applications

This paper presents a novel multi-Gb/s multi-mode LDPC decoder architecture and efficient design techniques for gigabit wireless communications. An efficient dynamic and fixed column-shifting scheme is presented for multi-mode architectures. A novel low-complexity local switch is proposed to implement the dynamic and fixed column-shifting scheme. Furthermore, an efficient quantization method and the usage of a one׳s-complement scheme instead of a two׳s-complement scheme are explored. The proposed decoder achieves very high throughput with minimal area overhead. Post layout results using TSMC 65-nm CMOS technology shows much better throughput, as well as better area- and energy-efficiency, compared to other multi-mode LDPC decoders.     

Interference Analysis and Transmit Power Control in IEEE 802.11a/h Wireless LANs

Reducing the energy consumption by wireless communication devices is perhaps the most important issue in the widely deployed and dramatically growing IEEE 802.11 WLANs (wireless local area networks). TPC (transmit power control) has been recognized as one of the effective ways to achieve this goal. In this paper, we study the emerging 802.11a/h systems that provide a structured means to support intelligent TPC. Based on a rigorous analysis of the relationship among different radio ranges and TPC's effects on the interference, we present an optimal low-energy transmission strategy, called MiSer, which is deployed in the format of RTS-CTS(strong)-Data(MiSer)-Ack. The key idea of MiSer is to combine TPC with PHY (physical layer) rate adaptation and compute offline an optimal rate-power combination table, then at runtime, a wireless station determines the most energy-efficient transmission strategy for each data frame transmission by a simple table lookup. Simulation results show MiSer's clear superiority to other two-way or four-way frame exchange mechanisms in terms of energy conservation.     

基于IEEE802.11a OFDM同步算法的FPGA实现

同步是OFDM系统中至关重要的一个环节,目前已有很多针对OFDM系统的同步算法,大致可以分为3类:基于嵌入符号中的导频、基于前导序列和基于循环前缀。提出了具体针对IEEE802.11a帧结构的同步算法(包括时间定时和频偏估计及纠正)。详细阐述了该算法各个模块FPGA的具体实现,具有复杂度低,便于工程实现的特点。     

Design of a lightweight authentication scheme for IEEE 802.11p vehicular networks

With the growing popularity of vehicle-based mobile devices, vehicular networks are becoming an essential part of wireless heterogeneous networks. Therefore, vehicular networks have been widely studied in recent years. Because of limited transmission range of wireless antennas, mobile vehicles should also switch their access points to maintain the connections as conventional mobile nodes. Considering the inherent characteristics of vehicular networks such as dynamic topology and high speed, the question of how to implement handoff protocol under real-time scenarios is very important. IEEE 802.11p protocol is designed for vehicular networks for the long distance transmission. To reduce handoff latency for 802.11p protocol, the authentication phase is waived during the handoff. However, security is also very important for wireless communications, and authentication can forbid access from malicious nodes and prevent wireless communications from potential attacks. Thus, in this paper, a lightweight authentication scheme is introduced to balance the security requirements and the handoff performance for 802.11p vehicular networks. In our scheme, the access points are divided into different trust groups, and the authentication process is completed in a group-based method. Once a vehicle is authenticated by an access point group, during the handoff within the same group, few extra authentication operations are needed. As a result, there is no extra overhead introduced to the authentication servers. Simulation results demonstrate that our authentication scheme only introduces small handoff latency and it is ideal for vehicular networks.     

IEEE802．11P：车载环境下的无线局域网

汽车在能够与路上相遇的汽车通信前,不能容忍长时间的建立连接而产生的延时,加上飞速行驶的汽车和复杂的道路状况给物理层带来了很大的挑战。IEEE802．11P的研究是基于IEEE802．11解决汽车网络的方案。由于设计的IEEE802．11标准在灵活性上很差,所以IEEE802．11p标准主要是解决快速连接高频率切换问题和新的安全问题。     

Efficient MAC strategies for the IEEE 802.11n wireless LANs

Current IEEE 802.11 wireless local area network (WLAN) standard products can provide up to 54 Mbps raw transmission rate, while non‐standard WLAN products with 108 Mbps have already appeared in the market, and the next generation WLAN will provide much higher transmission rates. However, the medium access control (MAC) was designed for lower data rates, such as 1–2 Mbps, and it is not an efficient MAC. Furthermore, a theoretical throughput limit exists due to overhead and limitations of physical implementations, and therefore increasing transmission rate cannot help a lot. Designing efficient MAC strategies becomes critical and important. In this paper, we introduce and propose a series of efficient MAC strategies to overcome the fundamental overhead, and to improve performance. The protocols and mechanisms include Direct Link Protocol, Without Acknowledgement, Without Retransmissions, Block Acknowledgement Protocol, Concatenation, Packing, Multiple Frame Transmission (versions 1 and 2) and Piggyback. The aim of this paper is to introduce and propose these efficient new MACs not only for current IEEE 802.11 standards (.11a/.11b/.11g), but also for the next generation WLAN with higher speed and higher throughput, especially for IEEE 802.11n. Copyright © 2006 John Wiley & Sons, Ltd.     

A Collision Alleviation Scheme for IEEE 802.11p VANETs

IEEE 802.11p protocol, also known as Wireless Access for the Vehicular Environment provides dedicated short range communication for future Vehicular Ad Hoc Networks (VANETs). According to the IEEE 802.11p standard, the highest priority traffic transmission often suffers from the consecutive collisions in bursty arrival or congested scenarios because of the naive pre-assumption of a low level of congestion in the system, and thus results in emergent messages delayed. In this paper, we propose a simple, but yet well performing collision alleviation scheme to alleviate intensive collisions between highest priority access categories which usually used to schedule emergency message since safety is the most critical and promising issue in VANET. In addition to theoretical analysis, simulations are conducted to evaluate its performance. The simulation results show that the proposed scheme can not only increase the achievable channel throughput of the legacy protocol at most 15%, but also reduce the average packet access delay of the legacy protocol at least 5% and the packet collision probability at most 60% in congested VANET environments.