共查询到20条相似文献,搜索用时 15 毫秒
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A real-time, microprocessor-based simulator was designed to study the packet transmission of voice on a broadcast type local area network, based on the CSMA/CD and Hymap multiple-access protocols. The speech quality is evaluated subjectively. A packetization-frozen protocol is used to eliminate the successive collisions due to possible synchronization of packet generation among stations. The variance of the network delay is bounded by discarding packets which have not been transmitted within a certain amount of time. Smooth speech output can be obtained by introducing additional buffer delay at the receiver. 相似文献
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Costas Busch Malik Magdon-Ismail Fikret Sivrikaya Bülent Yener 《Distributed Computing》2008,21(1):23-42
A MAC protocol specifies how nodes in a sensor network access a shared communication channel. Desired properties of a MAC
protocol are: it should be contention-free (avoid collisions); it should be distributed and self-stabilize to topological changes in the network; topological changes should be contained, namely, affect only the nodes in the vicinity of the change; it should not assume that nodes have a global time reference,
that is, nodes may not be time-synchronized. We give a set of TDMA-based MAC protocols for asynchronous wireless sensor networks satisfying all of these requirements. The communication complexity, number and size of messages,
for the protocols to stabilize is small, poly-logarithmic in the network size.
A preliminary version of the paper appears in the Proceedings of the 18th Annual Conference on Distributed Computing (DISC 2004), LNCS 3704, pp 245–259, Trippenhuis, Amsterdam, The Netherlands, October 2004. 相似文献
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Stuart Phillips 《Computer Communications》1984,7(1):12-16
Several models have been developed to assist with the design and understanding of distributed systems. The client-server model is used here to develop a set of requirements to be met by protocol sets used within a distributed system. An architecture within which protocols may be implemented to meet the requirements developed is proposed. A number of key requirements are reviewed and areas requiring further development identified. 相似文献
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介质访问控制(MAC)问题是水下传感器网络(UWSN)研究的热点问题之一,其协议设计的主要挑战是水下网络的信号传播延迟太高带来冲突的“时空不确定性”现象—来自不同站点的帧是否冲突不仅取决于他们的发送时间,还取决于这两个站点的位置.因此总结了水下MAC协议的最新研究成果,提出了一个基于位图协议的动态水下TDMA协议,适用于节点能够局部运动的动态水下网络.该协议利用水下特殊的“时空不确定性”现象减少信道空闲,提高能量效率和传输效率.最后,通过仿真实验验证了协议的可用性和效率. 相似文献
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An adaptive time division multiple access (TDMA) protocol for WDM passive star networks using fixed transmitters and tunable receivers is presented. The proposed optical adaptive TDMA (OATDMA) protocol is capable of operating efficiently under bursty and correlated traffic. According to the proposed protocol, the stations which are granted permission to transmit at each time slot, are selected by taking into account the network feedback information. In this way, the number of idle slots is minimized and the network performance is significantly improved. Furthermore, although the traffic parameters are unknown and time-variable, the portion of the bandwidth assigned to each station is dynamically adapted to the station’s needs. 相似文献
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Current developments in protocol standards for local area networks are not suitable for small microcomputers with limited storage and processing capability. A suitable distributed systems architecture that is based on datagrams is presented. Compatibility with the ISO/CCITT seven-layer OSI model is maintained where possible, and internetworking is supported. 相似文献
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A broadcast architecture network (Banet) suitable for distributed data processing is proposed. One feature of Banet is that the broadcast-within-a-group function is supported not only by the datalink level but by the transport or session-level network structure. The commitment control scheme is included in the network protocol. Design goals, physical structure and protocols are discussed. 相似文献
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无线传感器网络MAC协议对网络的生命期有着重要影响,为找到适合一定环境所使用的MAC协议,必须对不同的MAC协议进行必要的分析。从数据帧着手,分析了不同的基于TDMA的调度式MAC协议的差异。针对原有TDMA MAC协议数据传输量不高、实现难度大等问题,提出相应的改进方法,并对三个基于LEACH的TDMA MAC协议进行了仿真实现,仿真结果与数据分析的结果一致。 相似文献
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TDMA scheduling for event-triggered data aggregation in irregular wireless sensor networks 总被引:1,自引:0,他引:1
Multi-hop wireless sensor networks often use a TDMA schedule to collect data periodically from multiple locations within a large area. If the measurements from neighboring sensors are cross-correlated, they can be aggregated and compressed as they travel to the data sink. In order for data aggregation to occur quickly, the TDMA schedule must arrange time slot assignments in a certain order. The existing scheduling protocols cannot quickly obtain a schedule with this order, high concurrency, and no collisions. We propose a distributed TDMA scheduling protocol for data aggregation called DATP. In DATP, the sensor nodes transmit dummy packets in order to determine whether they can tolerate the interference from the other nodes that are assigned the same time slot. In this way, time slot allocations are empirically verified to be collision-free. In contrast, the existing protocols obtain schedules with collisions because they use unrealistic interference models such as neglecting interference generated more than two hops away. Furthermore, our simulations reveal that DATP achieves similar concurrency and lower execution time than comparable protocols. These simulations are executed for different network sizes, node densities, and data compression models. In addition, we show that, in networks with fluctuating links, DATP’s main advantage is its execution speed. 相似文献
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本文概述近几年兴起的卫星通信低速时分多址(TDMA)新技术。它与频分多址(SCPC,IDR/IBS,TES,VSAT)相比,以及与中速60Mb/s、高速120Mb/s TDMA相比,有许多独特优点。比较适合我国国情。本文简要说明其特点、技术难点以及这些难点如何解决,还介绍典型系统和设备性能参数,以便引起更多人兴趣,促进它的推广应用。 相似文献
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介绍和分析了无线Ad Hoc网络中自适应波束形成时分多址接入协议ABF-TDMA。ABF-TDMA是基于TDMA和智能天线技术来实现无冲突预约和波束形成,允许每对通信节点在每个时隙预约和训练来保证存在隐藏终端情况下的无冲突的预约和波束形成。成功预约和训练后,数据分组可以以自适应波束形成方式发送。本文分析了在全连通网络下不同分组长度、节点数和重发限制下ABF-TDMA的通过率和时延。仿真结果显示,ABF-TDMA可以获得高通过率、低时延、较小的时延抖动和丢包率,特别是分组长度较长和节点数较多情况下。 相似文献
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Transmission protocols like TCP are usually divided into a time scheduling and a data selection policy. We consider on-line algorithms of data selection policies for any time scheduling policy and any routing behavior in a network. For the model introduced by Adler et al. [Proc. 5th Israel Symp. on Theory of Computing Systems, 1997, pp. 64-72], we improve both the lower and the upper bound on the competitive ratio making them asymptotically tight. Furthermore, we present a lower bound that depends on the size of the buffers that are available both to the sender and to the receiver. We obtain a constant lower bound for the competitive ratio for constant buffer size. 相似文献
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本文研究了无线传感器网络最小空间重用链路调度(MSRLS)模型,给出了该模型的形式化描述,并在此基础上提出一种求解一般网络下MSRLS问题的集中式近似算法MSRLS-C。该算法同时考虑了无线传感器网络带宽需求分布和通信过程中的无线信道干扰,更适合真实网络。通过理论分析和实验对该算法的性能进行了论证和比较。 相似文献
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Phenomenal advances in nano-technology and packaging have made it possible to develop miniaturized low-power devices that integrate sensing, special-purpose computing, and wireless communications capabilities. It is expected that these small devices, referred to as sensors, will be mass-produced and deployed, making their production cost negligible. Due to their small form factor and modest non-renewable energy budget, individual sensors are not expected to be GPS-enabled. Moreover, in most applications, exact geographic location is not necessary, and all that the individual sensors need is a coarse-grain location awareness. The task of acquiring such a coarse-grain location awareness is referred to as training. In this paper, two scalable energy-efficient training protocols are proposed for massively-deployed sensor networks, where sensors are initially anonymous and unaware of their location. The training protocols are lightweight and simple to implement; they are based on an intuitive coordinate system imposed onto the deployment area which partitions the anonymous sensors into clusters where data can be gathered from the environment and synthesized under local control. 相似文献
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A modified version of the datagram capacity assignment of the FODA (fifo ordered demand assignment) access scheme, named FODA/IBEA, (information bit energy adaptive) is briefly presented. The main difference from the previous version (besides the fade countermeasure feature) is the possibility of the system to migrate, depending on the overall loading conditions, from a sort of fixed TDMA (time division multiple access) (called pre-assignment mode), in which each active station shares the spare capacity with all the others, to a more complex mechanism. The response of the system to a step of traffic at one of the active stations is studied, and the analytical expressions of the most significant variables are derived. The results of the analysis are first compared with the experimental ones and then used to show the sensitivity of the system's behavior with respect to some parameters. The possibility of adopting the capacity allocation algorithm in a distributed mode is also discussed. 相似文献