无限生机的无线接入网

本简要介绍ＷＣＤＭＡ、ＷＬＬ、ＬＤＭＳ（ＷＡＴＭ）和Ｏ／Ｗ ＷＬＬ等几种前沿ＷＬＬ技术。     

WATM-PRN互联网关缓冲容量对数据传输的影响

由于WATM沿用了ATM中部分流量控制机制,造成与一般非连接网络互联过程中,网关上两种不同网络控制协议处理的不一致。本文通过信真的手段分析了在WATM－PRN互联网关中缓冲容量对TCP－ABR和TCP－UBR数据传输性能的影响,以及在应用中的权衡。     

Physical Layer Design Alternatives for High Speed Outdoor Packet Radio Local and Medium Area Networks

In the last few years, the development of wireless local area networks (WLANs) has become a major goal in the field of computer and wireless communications. The Network Technologies Research group at the Communications Research Center in Canada has been working on a project to develop a high speed outdoor WLAN. In contrast to many existing WLANs, the new WLAN supports multimedia traffic such as voice, data and video; and will be used mainly in an outdoor environment with a cell coverage range of approximately 20 km. In this paper the physical layer design alternatives for the outdoor WLAN with a speed of 10 to 20 Mbps are described. Simulation results for some of the techniques considered to be used for the WLAN system are presented. The study is concluded by proposing two possible systems that one may consider for the implementation of a high speed outdoor WLAN. Although this study was primarily focused on WLAN applications, the results presented in this paper are applicable to several high speed wireless networks.     

用WATM技术增强GPRS网络系统

用WATM技术增强GPRS网络系统是为了让ATM先进的技术无缝地扩展到移动通信领域。通过对WATM技术的阐述,总结了在GPRS系统中引入WATM的主要办法,对GPRS系统的进一步深层次开发提供了新的思路。     

A Bandwidth Reservation Multiple Access Protocol for Wireless ATM Local Networks

A bandwidth reservation multiple access scheme(BRMA) is proposed to resolve contention and assignbandwidth among multiple users trying to gain access toa common channel such as in mobile users contending for resources in an ATM-based cellular networkor a wireless local area network (LAN) with shortpropagation delays. The protocol is best suited tosupport variable-bit-rate (VBR) traffic that exhibits high temporal fluctuations. Each mobile user isconnected end-to-end to another user over virtualchannels via the base station that is connected to thewired ATM B-ISDN network. The channel capacity is modeled as a time frame with a fixed duration.Each frame starts with minislots, to resolve contentionand reserve bandwidth, followed by data-transmissionslots. Every contending user places a request for data slots in one of the minislots. If therequest is granted by the base station through adownlink broadcast channel, the user then startstransmission in the assigned slot(s). The number ofassigned slots varies according to the required qualityof service (QoS), such as delay and packet lossprobability. A speech activity detector is utilized inorder to indicate the talkspurts to avoid wastingbandwidth. Due to its asynchronous nature, BRMA is ratherinsensitive to the burstiness of the traffic. Since theassignment of the minislots is deterministic, therequest channels are contention-free and the data channels are collision-free. Hence, in spite ofthe overhead (minislots) in each frame, BRMA provideshigher throughput than Packet Reservation MultipleAccess (PRMA) for the same QoS, especially for high-speed systems. A better delay performance is alsoachieved for data traffic compared to Slotted Alohareservation-type protocol PRMA. In addition, BRMAperforms better in terms of bandwidth efficiency thanthe conventional TDMA or the Dynamic TDMA, wherespeech activity detectors are very difficult toimplement.     

在WCDMA系统中实现ATM技术

WATM技术是为了让ATM先进的技术无缝地扩展到移动通信领域。通过对WATM技术的一定阐述 ,尤其是WATM对移动通信系统的支持 ,总结了在目前第三代移动通信WCDMA系统中引入WATM的主要办法。     

WATM资源分配调度和切换策略研究

近年来，ATM和无线通信两种技术得到了极为快速的发展。WATM（Wireless ATM）作为ATM网络的无线延伸的一种解决方案吸引了学术界和工业界广泛的兴趣。重点分析了WATM资源分配调度和对切换策略的研究。     

A New Transport Protocol for Broadcasting/Multicasting MPEG-2 Video Over Wireless ATM Access Networks

Because of the telecommunications de-regulation act and progress in wireless technologies, we will see the co-existence of heterogeneous broadband access infrastructures in the broadband video service industry in the near future. In this paper, we addressed the error control issue when transmitting MPEG-2 video streams over wireless access networks for broadband video broadcast or multicast services. An end-to-end transport protocol based on ATM and wireless ATM technologies is proposed. For video services, the underlying transport network should be transparent and quality should be maintained uniformly over all the segments whether wireline or wireless links. For network resources to be used efficiently, error control should be applied locally on the wireless segments so as to avoid the excessive overhead over the reliable wireline portions. Because a broadband video broadcast or multicast service is a one-to-multiple point service, FEC is the most prevalent error control mechanism. Due to the important role of MPEG-2 control information in the decoding process, priority MPEG-2 control information has to be differentiated from MPEG-2 data information, and excess error protection has to be allocated to it in order to achieve satisfactory QoS. Therefore, a header redundancy FEC (HRFEC) scheme for error control is applied at the local distribution centers before the MPEG-2 encoded video streams are transmitted over the wireless channels. HRFEC is an FEC-based selective protection scheme, which allocates extra error protection to important control information. Simulation results show that the quality of the reconstructed video sequence is vastly improved by using HRFEC, when the channel condition is poor.     

无线ATM网介质访问控制协议的研究

近年来无线ATM网络得到广泛研究,扩展ATM网络的宽带业务至无线环境面临许多方面的问题。介质访问控制(MAC)方法是无线ATM网的关键技术之一。MAC层协议的好坏直接影响系统性能和移动终端的复杂性。文中综合分析目前已有的无线ATM介质访问控制协议及方法,指出设计无线ATM网MAC层协议的三条原则,提出下一步研究方向。     

ATM战术网研究与发展

下一代的战术网（Ｔａｃｔｉｃａｌ Ｎｅｔｗｏｒｋｓ）是基于ＡＴＭ技术的。本文指出了把ＡＴＭ技术应用到战术环境中面临的主要问题;介绍了ＡＴＭ战术网及其典型范例ＰＯＳＴ－２０００;分析了无线ＡＴＭ协议体系,把ＡＴＭ战术网与无线ＡＴＭ进行比较;通过ＡＴＮＥＴ工程分析了未解决的问题和研究方向;展望了ＡＴＭ战术网的发展。