激光无线技术在Internet接入中的应用

介绍了激光无线技术在Internet接入中的优势，网络拓扑结构，调制和编码的方式以及传输波长的选择。     

Fixed wireless routes for Internet access

The author discusses the use of fixed radio access in urban and rural locations for Internet access. The costs involved are discussed and compared to wired access costs. The frequency bands available are considered as are the propagation conditions and antenna aspects     

Traffic handling capability of a broadband indoor wireless networkusing CDMA multiple access

CDMA (code division multiple access) may be an attractive technique for wireless access to broadband services because of its multiple access simplicity and other appealing features. In order to investigate the traffic handling capabilities of a future network providing a variety of integrated services, this paper presents a study of a broadband indoor wireless network supporting high-speed traffic using CDMA multiple access. The results are obtained through the simulation of an indoor environment and the traffic capabilities of the wireless access to broadband 155.5 MHz ATM-SONET networks using the mm-wave band. A distributed system architecture is employed and the system performance is measured in terms of call blocking probability and dropping probability, the impacts of the base station density, traffic load, average holding time, and variable traffic sources on the system performance are examined. The improvement of system performance by implementing various techniques such as handoff, admission control, power control and sectorization are also investigated     

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.     

Steady-State analysis of a split-connection scheme for Internet access through a wireless terminal

TCP does not perform well in a connection that includes a lossy wireless link. Techniques intended to improve the performance of TCP for such connections can be grouped into three categories: end-to-end, link layer and split-connection approaches. Some simulations and experimental results indicate that split-connection protocols yield better performance than the other two approaches. Although analytical modeling of the end-to-end and link-layer approaches has been presented, no comparable performance analysis for split-connection protocols has been reported previously. In this paper, a stochastic model is developed and used to analyze the performance of a class of split-connection protocols which deploy TCP on the wire-line network and a light-weight transport protocol on the wireless final hop. The final hop is provided by a digital TDMA cellular system. The condition of heavy source traffic to the wireless terminal is considered. The model relates the throughput and some useful auxiliary performance measures to key system parameters such as propagation delays, the base-station buffer size, the ARQ protocol and channel-error process of the wireless link. The usefulness of the analysis is illustrated by its application to the problem of sizing the TCP receiving buffer in a base station.     

移动无线互联网接入中视频编码率控制策略

建立了用于移动无线互联网接入的视频编码转换模型,提出了自适应运动矢量估值方法.将编码转换码率控制分为图像层控制和宏块层两级,首先在总体上对每帧图像的编码比特数进行预分配,然后采用小波变换系数来表征图像特征,为帧内不同特征的宏块选用不同的量化因子,提出了一种新的码率控制策略.模拟实验表明:该方法在视频图像质量没有明显失真的前提下,提高了视频编码转换速度;编码转换输出码流和编码转换缓冲区占用量较稳定,重建图像的信噪比得到了明显的改善.     

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     

Spectrum resource allocation for wireless packet access withapplication to advanced cellular Internet service

The advanced cellular Internet service (ACIS) is targeted for applications such as Web browsing with a peak downlink transmission rate on the order of 1-2 Mbits/s using a wide-area cellular infrastructure. In order to provide bandwidth on demand using scarce radio spectrum, the medium-access control (MAC) protocol must: 1) handle dynamic and diverse traffic with high throughput, and 2) efficiently reuse limited spectrum with high peak rates and good quality. Most of the existing approaches do not sufficiently address the second aspect. This paper proposes a dynamic packet assignment (DPA) scheme which, without coordinating base stations, allocates spectrum on demand with no collisions and low interference to provide high downlink throughput. Interference sensing and priority ordering are employed to reduce interference probability. A staggered frame assignment schedule is also proposed to prevent adjacent base stations from allocating the same channel to multiple mobiles at the same time. Simulation results based on a packet data traffic model derived from wide-area network traffic statistics, which exhibit a “self-similar” property when aggregating multiple sources, confirm that this method is able to reuse spectrum efficiently in a large cellular system having many users with short active periods. Distributed iterative power control further enhances spectrum efficiency such that the same channel can be simultaneously reused in every base station     

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.     

ZigBee无线局域网与Internet的接入设计

为了实现对ZigBee网络远程监控,讨论了在ZigBee网络中采集的物品信息如何用GPRS接入Internet的方式,从而实现远程对ZigBee无线局域网络的信息监测与控制。     

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…     

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.     

Multiple access protocol for power-controlled wireless access nets

We consider ad hoc wireless networks that are configured as Mobile Backbone Networks. A hierarchical network architecture is synthesized, consisting of Access Nets (ANets) and Backbone Nets (BNets). Each ANet is managed by a (dynamically elected) Backbone Node (BN) that is equipped with higher capability (transmission and processing) modules. The BNs are chosen from currently active mobile backbone-capable nodes or are represented by (ground and/or airborne) unmanned vehicles (UVs) that are guided into selected positions. We develop and investigate a new joint power controlled medium access control (MAC) algorithm for wireless access nets (ANets). Under our new protocol, the net backbone node instructs the ANet nodes to make power control adjustments while simultaneously allocating to them slots for the requested transmissions of their packets. This algorithm, in contrast to other employed conventional graph-based scheduling algorithms, satisfies the requirement that a minimum signal-to-interference and noise ratio (SINR) is met at all intended receivers. We show our algorithm to lead to a significant increase in the net throughput level by attaining high spatial reuse.     

TDMA multiplexing of ATM cells in a residential access SuperPON

Time division multiple access (TDMA) multiplexing of ATM cells from thousands of residential customers toward the common feeder of a passive optical network (SuperPON) tree obviates the need for an equal number of optical line terminations (OLTs). All upstream transmissions converge by means of the passive splitters/combiners to just one OLT unit which serves all by time sharing. The ability to reach such a high splitting ratio became possible by the development of bursty mode optical amplifiers (OAs). In addition, OAs make possible a 100-km-long feeder which can bypass the local exchange into the first core switch, bringing further savings to both initial and running costs. These techniques allow SuperPONs to lower the access cost per customer, holding for the promise of ushering into domestic local loops the photonics revolution which has already transformed the transmission plant. These savings, however, can only be realized under the assumption that the system can accept high loading before exceeding the limits of quality of service (QoS) requirements and without distorting the egress traffic in a way that jeopardizes the statistical estimates on which ATM connection acceptance was based. Solutions to the problem of traffic arbitration, respecting the idiosyncrasies of each traffic class and suitable for fast implementation, are offered     

A millimeter wave broadband wireless access technology demonstratorfor the next generation Internet network reach extension

We report design and implementation scenarios for a gigabit-capacity and high-data-rate fixed wireless access technology demonstrator. The system is based on a broadband wireless access concept and implementation techniques utilizing millimeter-wave and newly introduced free-space optical wireless high-speed links. The demonstration platform is to provide broadband “last mile” access and networking solutions to Internet users in densely populated areas with homes and businesses (e.g., building-centric and inner city environments) in need of high bandwidth not served by the fiber infrastructure. The investigation focuses on the radio link design, network architecture, system integration, and a compatible interface to the existing ATM fiber and satellite core networks in support of the next-generation Internet (NGI) reach network extension by the wireless technology     

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.     

Building the wireless Internet

Everybody's talking about the wireless Internet, but what on earth is it? And who's building it? The trade press is adrift in a bewildering jumble of acronyms from the cellular telephony industry that claim to point the way. Or maybe dozens of LEOS (low-earth-orbiting satellites) will furnish the wireless Internet. Or perhaps it's really two way pagers on steroids-powered by WAP (the wireless access protocol). Proceeding from first principles, the author believes that none of the well-known technologies will, in the end, provide the wireless Internet. Instead a dark-horse technology-a “pure Internet” system based on technology familiar from a multitude of wireless local-area networks (LANs)-has good grounds to prevail. The author discusses which RF frequency bands should be used for the Internet, the use of nanocells to build the network, and gives a brief outline of the economics involved     

Internet of Things-based wireless sensor networks for monitoring access constraint security measures in liable data aggregation

A wireless sensor network (WSN) is a network of autonomous, small sensors that can detect, collect, and send data about their surrounding environment. In the Internet of Things (IoT) infrastructure, WSNs are the smart devices that provide the platform with resource input. Security breaches and insider attacks are possible due to the WSN's resource-constrained design. However, the IoT platform's intelligence may be extended to WSN nodes for managing device and data-level security. This paper proposes Monitored Access Constraint Security (MACS) to ensure the privacy of data collected via the ubiquitous processing enabled by the Internet of Things. The IoT platform performs frequent checks on the quality of the interactions between the various nodes to ensure that they are functioning properly and that the sensor aggregation instances are accountable. Node liability is considered while adjusting the aggregate level and the continuity. The method guarantees secure information from the environment and the data sources. The quality of the data gathered in the suggested technique is evaluated based on node liability and information extraction feature. Accordingly, security measures are implemented at data gathering and filtering levels and then assessed using a recurrent learning process. Since there are fewer security breaches overall, the rate of aggregation increases. Aggregation loss, delay time, false rate, throughput, and verification time are used to evaluate the performance.     

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.     

Fixed wireless access: a market and system overview

Amongst the many technological developments of the last few years, one in particular has been directly driven by the liberalisation of the telecommunication services sector and the entry of competition into once monopoly markets. That technology is fixed wireless access (FWA). While traditional telecommunication infrastructures have relied on the use of twisted pair copper wire to deliver services to subscribers-the local loop-FWA replaces this with point-to-multipoint digital wireless links. This paper examines the history of Nortel's involvement as market leader in this sector from its earliest days, the approaches the company has taken to the technologies involved and explores FWA's potential in the world's deregulating telecommunication services market