一种面向会展中心的无线自组网MAC层协议的设计

文中研究了无线令牌环协议,将MAC层的WTRP协议应用于无线自组网中,采用WTRP协议优化了会展企业中心无线自组织网络.重点介绍了WTRP协议的状态机以及控制机制,模型中的节点通过令牌获得网络的使用权,而令牌在节点之间传递,并以公平和效率为原则.网络仅需要时令牌进行管理和维护,而不需要对网络中的数据进行管理,使得数据在网络中进行透明的传输,增加了网络的保密性.通过仿真验证了模型的正确性,减少了数据包在网络节点中的等待时间,使得会展企业活动越来越便捷.     

分布式无线令牌环接入技术在无线自组网中的应用研究

本文在无线令牌环协议(WTRP)的基础上,提出了一种在无线自组网中无竞争的分布式无线令牌环协议(DWTRP),仿真实验表明该协议的排队等待延迟和等待队列长度均比WTRP有很大降低,稳定性大大增强。     

采用动态令牌的MANET多址接入协议

本文设计了一种采用动态令牌算法的MANET多址接入协议,解决了隐藏终端和入侵终端问题.利用这种算法,不再需要为令牌的传递预先建立虚拟的令牌逻辑环路,而是根据当前的网络拓扑结构自动地形成令牌的传递路由,使得令牌的传递能够适应网络拓扑结构动态的动态变化.同时,通过周期性地产生令牌并严格地限制每个令牌的生存时间,简化了令牌的维护过程,并为时延敏感的业务提供良好的QoS保障.另外,该协议采用一种互同步技术,具有成本低廉、运行可靠的特点,可完全独立于其它系统(如GPS等),且已应用于实际的MANET网络.     

移动Ad hoc网络轮询接入控制协议

该文对Ad hoc网络的MAC层协议进行了研究,通过对无线令牌环协议(WTRP)进行改进,提出了一种新的具有QoS保障的无竞争的分布式并行无线轮询访问协议(DPWPAP),并采用嵌入Markov链和概率母函数的分析方法,用限定服务规则进行了系统建模,在系统模型的基础上得到了系统的平均排队队长以及平均等待时间的解析结果.理论分析和仿真结果是一致的,表明该协议的排队等待延迟和平均等待队列长度均比WTRP有很大降低,稳定性大大增强,更加适用于对时延要求较高的业务.     

高动态Ad Hoc路由协议性能分析

Ad Hoc网络是一种没有固定设施的无线移动自组织网络,动态变化的拓扑结构对路由协议的性能有着重要影响。研究了动态源路由(DSR)协议、Ad Hoc按需距离矢量(AODV)路由协议和最优链路状态路由(OLSR)协议3种传统路由协议,利用OPNET软件作为仿真工具,设计了2种不同网络规模条件下空中飞行平台网络拓扑结构背景的高动态仿真方案,通过比较网络时延、归一化网络吞吐量、路由负载和数据传送成功率,分析了它们的性能。仿真结果表明,OLSR协议的综合性能优于其它协议,更适合于节点高速移动且网络拓扑结构频繁变化的Ad hoc网络,并为下一步研究打下基础。     

一种基于收集树协议的工业无线传感器网络动态路由机制

无线HART(Highway Addressable Remote Transducer)是当前工业无线传感器网络中应用最为广泛的协议,但无线HART没有提供动态路由机制以满足对工业无线网络应用至关重要的稳定性和鲁棒性。该文在无线HART协议基础上,提出一个基于收集树协议的可应用于工业无线传感器网络的动态路由机制。它占用时分多址(TDMA)超帧中的前几个时间片来产生和维护网络拓扑。通过仿真实验从3个方面对该动态路由机制进行了评估:拓扑生成时间,链路质量及网络拓扑的稳定性。仿真和评估结果表明该动态路由机制可以在基于TDMA的工业无线传感器网络中应用。     

低WSN服务能耗的MAC协议实现

为解决WSN服务能耗和服务质量问题,提出了一种无线传感器网络介质访问控制协议WTRP-S,分析比较了WTRP-S,WTRP和IEEE802.15.4MAC的性能,建立了节点启动调度模型。仿真结果表明:在数据业务大的网络中,该协议既能保证服务质量,在节点关闭通信模块中能够节省更多能量,使得整体能耗降低,WTRP-S适用于能量受限的无线传感器网络。     

基于动态令牌轮询提供视频QoS 保证的无线ATM多址接入控制

本文提出了一种基于动态令牌轮询调度算法（DTSA）的无线多址接入控制（MAC）机制,该方案应用于无线ATM系统,为多媒体业务提供了服务质量（QoS）保证的无线接入.基站控制器为每个ATM连接建立令牌模型,根据模型进行时隙分配.为了适应诸如压缩视频流等实时VBR业务的动态特性和严格的QoS要求,定义了移动站用于通知基站其源帧率变化及队列情况的紧急消息.一旦收到紧急消息,基站将分配一定数目的令牌进入紧急令牌队列.根据结合紧急令牌队列的令牌轮询调度机制,基站可以进行灵活的时隙分配.通过仿真计算,我们发现该机制能较大地提高实时VBR业务的时延和丢失性能.本文还就影响该机制性能的设计参数进行了分析.     

一种多信道的分簇式短波令牌协议

传统的短波令牌协议( HFTP)调度方式单一,在没有数据传送时,信道资源会被各节点间的令牌传递所占用,且令牌在通信质量较差时易丢失。基于此,提出一种多信道的分簇式短波令牌协议( CHFTP),通过以通信质量评估为标准的分簇算法和基于预约的动态令牌调度,减小了令牌丢失的概率和令牌传递、处理的开销,并给出了仿真分析。仿真结果表明,该协议的端到端平均时延和网络吞吐量明显优于短波令牌协议, CHFTP 的平均时延最多可减少75%,网络吞吐量最多可增加66.7%,适合在短波通信网络中使用。     

基于ZigBee的认知路由协议研究

本文针对传统无线传感器路由协议在某个节点能量消耗大,路由效率低的问题提出一种基于Q学习算法的认知路由协议模型。本文使用OPNET网络仿真软件作为仿真平台,与原协议的路由状况进行对比,改进后的路由协议提高网络对节点动态能量消耗的适应能力,从而改善整个网络能耗和网络时延问题。     

IWTRP: Spatial-reuse Enhancement of the Wireless Token Ring Protocol

This work presents an improved wireless token ring protocol (IWTRP) for wireless metropolitan area networks (W-MANs) adopting a ring topology. Opposed to the single token and transmission permitted in WTRP, IWTRP provides a novel method to allow for multiple tokens, and thus multiple simultaneous transmissions in the ring. IWTRP employs both the request-to-send/clear-to-send (RTS/CTS) handshaking and the network allocation vector (NAV) updating techniques to resolve collision-resolution and token-elimination problems resulted from multiple tokens. The normalized saturation throughput of IWTRP is analytically characterized and verified through simulations.     

WTRP - wireless token ring protocol

The wireless token ring protocol (WTRP) is a novel medium access control (MAC) protocol for wireless local area networks (WLANs). In contrast with IEEE 802.11 networks, WTRP guarantees quality of service (QoS) in terms of bounded latency and reserved bandwidth, which are critical in many real-time applications. Compared to 802.11, WTRP improves efficiency by reducing the number of retransmissions due to collisions, and it is more fair as all stations use the channel for the same amount of time. Stations take turns transmitting and give up the right to transmit after a specified amount of time. WTRP is a distributed protocol that supports many topologies, as not all stations need to be connected to each other or to a central station. WTRP is robust against single node failures, and recovers gracefully from multiple simultaneous faults. WTRP is suitable for interaccess point coordination in ITS DSRC, safety-critical vehicle-to-vehicle communications, and home networking, and provides extensions to other networks and Mobile IP.     

Security Attack Safe Mobile and Cloud-based One-time Password Tokens Using Rubbing Encryption Algorithm

One-time Password (OTP) Token has become one of the main stream security products during the past few years. OTP Token can automatically generate a random password. It is especially popular to be used with the Two-factor Authentication (2FA) system. OTP Token has proliferated into many different form factors such as standalone token, PC, PDA, cellular phone and Cloud-based token. But most of the implementation has their short comings with high token cost, not easy to carry and high supporting or deployment cost. Certain implementations may also compromise the network security when the token is lost or stolen. Moreover, most of the tokens can be broken-in by Man-in-the-Middle Seed-tracing and Shoulder-surfing security attacks. To overcome such aforementioned issues, we propose a secure encryption algorithm – Rubbing Encryption Algorithm (REAL). We use REAL to implement a Mobile-based and a Cloud-based OTP Token as design examples. Both of them are of high security level, lower total token cost and can resist the aforementioned security attacks as well.     

ISO 8802/5 token ring local-area networks

Token ring networks are the second most commonly used type of local-area network (LAN). The second version of the formal token ring multiple access mechanism, ISO 8802/5, was released in late 1995 and this rationalised many of the new developments, e.g. the 16 Mbit/s solutions. The latest innovations are the full duplex dedicated token ring and the development of a 100 Mbit/s high-speed token ring solution. To many people's surprise there is an extensive legacy of token ring installations and the latest innovations, such as token ring switching, are an attempt to maintain and support this significant market presence. Token ring is designed to provide high throughput under heavy loads (something which is normally impossible for Ethernet to sustain) but in most cases it is used in typical office environments where there is infrequent occurrence of heavy loads     

A novel fault tolerant token ring network

Token Ring Networks have gained popularity due to their simplicity and ease of maintenance. However, the functioning of the entire network is dependent on the well being of an entity called “token”. The network ceases to function if the token is lost. There are algorithms suggested for improving the fault tolerant capabilities of the network with respect to the token.This paper proposes an algorithm to achieve fault tolerance. The algorithm is implemented on a simulated token ring network.     

A scalable and energy‐efficient MAC protocol for sensor and actor networks

A scalable energy‐efficient MAC protocol is proposed for wireless sensor and actor networks (WSAN) to improve the network performance. Actor's placement has computed using midpoint K‐mean technique. These actors perform as the cluster heads and collect the information from its members. Cluster head computes the shortest path to all of its cluster members. Further, it divides the cluster into multiple subtrees and assigns a noninterference channel to every subtree. A token is assigned to each subtree for intracluster communication. Token handling and token processing mechanisms are proposed to transfer token from one node to next eligible node. Finally, a throughput‐based channel selection mechanism has proposed for actor‐actor communication. The proposed protocol is simulated in NS2 and compared with its competitive MAC protocols. The results describe that the existing protocols are out beaten by the proposed mechanism.