分布式无线网络中依据用户妥善安排的多址接入协议

基于有效竞争预约接入、无冲突轮询传输的思想，提出了支持节点移动性和多跳网络结构的UPMA(User—dependent Perfect—scheduling Multiple Access)协议．其指导思想是仅有发送分组的节点才竞争接入使用信道资源，无业务发送的节点将立即被取消占用信道的资格，因此它极大地提高了信道的使用效率；同时，提出了一种冲突避免和分解协议来保证节点能快速接入信道；最后，以星型拓扑结构的网络为例考察了它对Internet数据业务的支持性能，并且给出了相关的结论．     

Ad Hoc网络中基于信誉机制的介质访问控制协议

分析802.11协议存在的主要安全隐患,对协议进行必要的改进,提出基于信誉的多令牌介质访问控制协议,通过攻击检测和通信行为监测建立网络节点的信誉机制。以此为依据进行多令牌管理,规定只有持有令牌的节点才能访问信道,从而实现具有安全性保障的介质访问控制。利用NS进行仿真,结果表明该协议能够检测到网络中节点的恶意行为并迅速做出反应,较好地保证了网络性能。     

过程TPN模拟方法用于两种现场总线网络的性能比较研究

以具有过程说明的TPN为工具,对两种不同类型的Fieldbus网络性能进行了研究、分析 和比较.在轮询协议中,采用了P/C通信模型,由主节点管理轮询队列;在令牌协议中,分别 采用循环令牌和授权令牌来满足周期性和突发性通信需要,其中对网络响应时间、吞吐量和振 颤等性能进行了重点讨论,给出了它们的性能差异和响应界限.     

Internet无线接入网络中应用智能天线的多址协议及性能分析

该文研究将智能天线应用于Internet无线接入网络的中心接入点(CAP)。提出了基于轮询的自适应波束形成多址接入协议(PB-ABFMA)．该协议中,CAP接收或发送数据分组前,由CAP引导用户节点发送训练序列,CAP的智能天线据此计算出与用户节点对应的权矢量．CAP以轮询及动态TDMA方式为各节点安排发送时隙。采用微时隙为处于空闲状态的节点保持连接以降低时延．设计了一种简单有效的竞争接入算法,保证新用户能快速接入信道．针对Internet中主要的“请求一回应”(request-reply)式业务,分析了协议的信道利用率与平均“请求一回应”时延．结果表明,PB-ABFMA协议能有效支持智能天线应用并具有较高的信道利用率与良好的时延性能。     

短波地空IP网络的MAC协议设计与仿真

合适的多址接入MAC(multiple access)协议是提升网络性能的关键。根据短波地空IP网络通信覆盖范围广、难同步,空中节点信息可能丢失的特点,设计出该网络一种新型的带预约短波令牌协议HFTP-R(High Frequency token protocol with reserve)。该协议在初始化时由空中节点随机加入地面节点形成的簇,并通过预约信道向地面节点发送预约信息,从而获取令牌接入信道,地空之间不需要保持逻辑环的"封闭性"。最后,利用OPNET软件构建了HFTP-R的仿真框架,与其他MAC协议作了仿真比较。仿真结果表明,HFTP-R减少了短波令牌协议HFTP(High Frequency token protocol)的令牌丢失次数和传递开销,能提供较好的实时性、较高的网络吞吐量和业务传输成功率,在特定需求下较其他MAC协议更有优势,可满足网络需要。     

车载自组织网络中基于时分复用的异步多信道MAC协议

为解决车载自组织网络负载较重时控制信道拥塞和信道利用率低的问题,提出一种时分复用机制的异步车载自组织网多信道MAC(Media Access Control)协议-ATMP (Asynchronous TDMA-based multi-channel MAC Protocol).ATMP协议采用时分复用的异步接入机制实现节点分时段接入控制信道,减少并发接入控制信道的节点数目,降低碰撞概率;进一步,为了解决多信道协调信息丢失问题,ATMP协议使用节点协作机制来获取节点遗漏的信道协调信息,有效降低因协调信息缺失造成的数据信道服务信息碰撞概率.仿真结果表明,ATMP协议在碰撞概率、安全消息时延及控制信道吞吐量指标上优于IEEE 1609.4标准、AMCP协议和AMCMAC协议.     

基于EPA控制网络的ZigBee无线接入研究与实现

分析了ZigBee接入EPA的网络模型,并针对节点需要周期性发送数据的特定无线传感器网络应用,提出了基于周期性的消息调度算法.该算法通过采用令牌和轮询相结合的集中式消息调度模型,构建节点周期性消息发送调度机制,保证节点之间无冲突地使用无线信道,是一个确定性的消息调度机制.该算法已应用于ZigBee-EPA接入点,实际运行良好,具有较好的性能.     

IEEE802.11p/1609.4多信道协作机制改进研究

IEEE 802.11p/1609.4是车联网的专用接入访问控制协议。针对IEEE 802.11p/1609.4标准协议中多信道协作机制存在信道资源浪费、竞争信道拥塞等问题,在划分车载单元与路侧单元优先级的基础上,提出一种改进的多信道协作机制。将控制信道划分为注册时隙(RI)和轮询时隙(PI),RI节点利用服务信道提高空闲信道资源利用率,PI通过轮询列表在控制信道发布安全消息消除信道竞争。在Matlab和OMNET++的仿真环境下进行验证,结果表明改进机制在安全消息传输率、平均传输时延、服务信道吞吐量和消息丢失风险指数方面均有明显的性能提升,并且在高节点密度情况下,仍能保证消息传输效率。     

一种新的拓扑无关的按需分配多信道自组网MAC协议

本文针对节点具有多个可用信通的自组网,提出了一种与拓扑无关的多信道MAC接入协议,协议采用按需预约的方式进行动态的信道分配,通过携带在信道预约消息中的节点邻居状态信息实现节点信道状态的更新。该协议所需信道数与网络的拓扑和度无关,克服了拓朴相关的多信道MAC协议不适用于节点密集的应用场合的问题。在协议开销增加很小的情况下,每个节点只需要一部半双工收发信机就能够实现在多个信道上高效的数据收发,不需要节点间的时钟同步,极大地降低了对网络节点设备的硬件要求,具有良好的应用前景。仿真结果表明,协议在网络总吞吐量、端到端时延等方面具有优良的性能。     

一种基于认知无线电的自组网多信道MAC协议

针对节点具有多个可用信道的自组网的信道资源利用率问题,提出了一种基于认知无线电的MAC接入协议,协议根据网络中节点的邻居关系,通过认知推理对两跳邻居范围内的不同网络节点分配不同的驻留信道,驻留信道的选择考虑了避免信道干扰和冲突,每个节点只需要两部半双工收发信机就能够实现在多个信道上高效的数据收发.仿真结果表明,协议在网络总吞吐量、端到端时延等方面具有优良的性能,能很好地适用于节点密集的应用场合.     

Performance investigation of a token passing access protocol for a multichannel optical fibre LAN

An alternative approach to multichannel local area network access is described. The new multichannel access scheme or protocol is based on a token passing arbitration policy. It is specifically intended for use with a starconfigured optical fibre LAN employing wavelength division multiplexing technology in order to provide a multichannel transmission medium. The multichannel network architecture comprises a single reservation channel and several equivalent speed data channels. Delay versus throughput performance characteristics for the network obtained by both analysis and discrete event simulation are shown. The multichannel token passing protocol is found to significantly improve these characteristics in comparison with a conventional single channel token passing approach using the same overall network transmission rate (i.e. the sum of the individual channel bit rates in the multichannel case). Furthermore, when the end-to-end propagation delay for an individual channel on the network becomes large, the multichannel token passing protocol is shown to exhibit an improved delay versus throughput performance over a multichannel protocol employing carrier sense multiple access with collision detection.     

接入网MAC层QoS系统的多业务令牌桶流量整形算法

以HFC网络核心设备双向CM(Cable Modem)为研究背景,首先对目前的流量整形算法进行了分析,在HFC网络QoS系统需求的基础之上,提出了一种动态支持多业务整形的令牌桶算法.以美国有线电视实验室的测试用例仿真分析了队列长度对丢包率以及延时的影响.通过性能分析可以看出,该算法满足了多种应用对延时和丢包率的要求,很好地调整了数据的突发速率,有效地进行了流量整形控制.     

一种TDMA无线传感器网络MAC协议能量有效性分析

经典轮询协议作为一种TDMA型MAC协议,符合无线传感器网络节约能量的要求,但在网络伸缩性上有所不足。在此基础上得出一种更适用于无线传感器网络的Controllable Threshold Polling MAC协议(CTP-MAC),使得网络能够自主完成时隙分配;结合概率母函数的方法,建立网络能量有效性的分析模型,得到平均功率的近似计算公式,对经典门限服务轮询协议和C"I'P-MAC进行分析。通过仿真实验,验证了分析模型的有效性。     

Hard Real-Time Communication with the Timed Token Protocol: Current State and Challenging Problems

With the increasing use of distributed real-time systems, the ability of communication networks to handle real-time traffic is becoming more and more important. The timed token medium access control protocol, which has been now incorporated into several network standards such as FDDI and SAFENET due to its special timing property of bounded medium access time, is one of the most suitable and attractive candidate communication protocols for supporting distributed hard real-time applications. Extensive research has been conducted on using the timed token protocol to guarantee timely transmission of messages in a communication environment with hard real-time requirements. This paper intends to present a comprehensive review on recent advances in hard real-time communication with the timed token protocol. In addition, several challenging problems are identified.     

A Priority-aware Frequency Domain Polling MAC Protocol for OFDMA-based Networks in Cyber-physical Systems

Wireless networking in cyber-physical systems (CPSs) is characteristically different from traditional wireless systems due to the harsh radio frequency environment and applications that impose high real-time and reliability constraints. One of the fundamental considerations for enabling CPS networks is the medium access control protocol. To this end, this paper proposes a novel priority-aware frequency domain polling medium access control (MAC) protocol, which takes advantage of an orthogonal frequency-division multiple access (OFDMA) physical layer to achieve instantaneous priority-aware polling. Based on the polling result, the proposed work then optimizes the resource allocation of the OFDMA network to further improve the data reliability. Due to the Non-polynomial-complete nature of the OFDMA resource allocation, we propose two heuristic rules, based on which an efficient solution algorithm to the OFDMA resource allocation problem is designed. Simulation results show that the reliability performance of CPS networks is significantly improved because of this work.      

分布式无线网络轮询多址等待时间策略控制研究

基于预约轮询接入的思想,提出了TPMA(Time—dependentPerfectschedulingMultipleAccess)协议,其控制原则是有信息分组的节点进入轮询队列,群内中心节点选择出有最长等待时间分组的节点,并按照门限服务规则进行无冲突发送。实验仿真证明,该方案减小了信息分组的平均等待时间,明显改善了系统性能。     

An adaptive polling interval and short preamble media access control protocol for wireless sensor networks

Media access control (MAC) protocols control how nodes access a shared wireless channel. It is critical to the performance of wireless sensor networks (WSN). An adaptive polling interval and short preamble MAC protocol (AX-MAC) is proposed in this paper. AXMAC is an asynchronous protocol which composed of two basic features. First, rendezvous between the sender and the receiver is reached by a series of short preambles. Second, nodes dynamically adjust their polling intervals according to network traffic conditions. Threshold parameters used to determine traffic conditions and adjust polling intervals are analyzed based on a Markov chain. Energy consumption and network latency are also discussed in detail. Simulation results indicate that AXMAC is suited to dynamic network traffic conditions and is superior to both X-MAC and Boost-MAC in energy consumption and latency.