共查询到19条相似文献,搜索用时 50 毫秒
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Ad hoc网络的体系结构及其设计 总被引:8,自引:0,他引:8
Adhoe网络体系结构的设计问题目前仍无定论,但是有一点是可以确定的,即应采用不同于传统网络的体系结构。首先阐述Ad:hoe网络的节点结构,比较了几种典型的网络结构,然后给出了一种用于Adhoe网络的通用协议栈。接着详细地讨论了Ad:hoe网络体系结构的设计策略、原则和方法,最后对全文进行了小结并给出了今后的工作方向。 相似文献
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Ad hoc网络体系结构的设计问题目前仍无定论,但是有一点是可以确定的,即应采用不同于传统网络的体系结构。首先阐述Ad hoc网络的节点结构,比较了几种典型的网络结构,然后给出了一种用于Ad hoc网络的通用协议栈。接着详细地讨论了Ad hoc网络体系结构的设计策略、原则和方法,最后对全文进行了小结并给出了今后的工作方向。 相似文献
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基于IEEE 802.11高速无线局域网的速率自适应MAC协议研究 总被引:3,自引:0,他引:3
目前的IEEE 802.11标准在物理层提供了对多种发送速率的支持,然而在MAC层却没有规定速率自适应的方法。该文研究了高速IEEE 802.11 无线局域网中的速率自适应方案。首先,提出了EACK协议,EACK使用基本速率发送MAC头,并在ACK帧中携带信道信息,因而能够较快速地响应信道的变化,同时具有少的开销;其次,在EACK基础上,提出了一种恒定发送时间(CEACK)的策略,CEACK能够克服传统IEEE 802.11 DCF MAC协议的理论吞吐量上限,并且具有更好的时间公平性能,能够应用于高速的无线局域网。 相似文献
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一种基于IEEE 802.11的多速率自适应MAC协议 总被引:2,自引:0,他引:2
提出了一种新颖的基于连续ACK帧统计信息的IEEE 802.11多速率自适应MAC协议EARF(EnhancedARF),其主要思想是:每一个速率有各自的成功阈值——速率升高的门限值,并且该值根据信道状况(用延时因子量化)动态地变化。协议不需对现有的IEEE 802.11标准做任何修改,因此易于通过编写驱动程序实现。仿真表明在大多数信道条件下,该协议性能较现有的基于ACK帧统计的速率自适应协议如ARF,ARF3-10都有较大的提高。 相似文献
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由于无线链路和拓扑结构的时变特性,隐终端和暴露终端问题,Ad hoc网络的优化设计是一个很复杂的问题,跨层设计的提出就是为了解决这个难题。文章介绍Ad hoc网络跨层设计的提出背景,理论依据以及跨层设计的原则和目标,提出一种较合理的跨层设计模型,分析了跨层设计中存在的关键问题。 相似文献
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Adhoc网络中的MAC协议是一个比较复杂的问题。本文首先分析了Adhoc网络中实施MAC协议的各种困难,然后详细讨论了隐终端和暴露终端问题。最后比较分析了目前提出的几种Adhoc环境下的MAC协议并给出了结论。 相似文献
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为有效减小Ad Hoc网络实时业务节点的信道接入时延,提升对多媒体业务的服务质量(QoS)保障,在研究时隙分配类多址协议的基础上,设计了一种新的基于时隙重构的分组预约协议。新协议时隙结构简单,具有较好的冲突化解能力,通过对空闲数据时隙的重构利用以及层级式的接入控制,取得了较好的时延保障性能。 相似文献
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该文提出一种新的MAC协议,其目的是增加802.11b的网络容量。虽然IEEE的802.11b协议提供了较高的原始速率,但是物理层和MAC层随速率提高而引入的额外开销也不断增大。此外,物理层规范定义了两种物理层数据单元格式,但是研究者没有研究如何利用开销小的物理层数据单元来提高802.11b的容量。该文提出一种物理层自适应的算法,它能自适应地选择802.11b物理层规范中的两种不同物理层数据单元格式进行传输,并计算相应的网络分配向量。通过NS仿真证明,该协议能够提高网络的性能,如端到端的时延,有效吞吐量和传包率,特别是在高负载,高速率情况下。 相似文献
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Wanrong Yu Jiannong Cao Xingming Zhou Xiaodong Wang Chan K.C.C. Chan A.T.S. Leong H.V. 《Wireless Communications, IEEE Transactions on》2008,7(1):135-145
One way to improve the throughput of a wireless ad hoc network at the media access (MAC) layer is to allow as much as possible concurrent transmissions among neighboring nodes. In this paper, we present a novel high-throughput MAC protocol, called Concurrent Transmission MAC(CTMAC), which supports concurrent transmission while allowing the network to have a simple design with a single channel, single transceiver, and single transmission power architecture. CTMAC inserts additional control gap between the transmission of control packets (RTS/CTS) and data packets (DATA/ACK), which allows a series of RTS/CTS exchanges to take place between the nodes in the vicinity of the transmitting or receiving node to schedule possible multiple, concurrent data transmissions. To safeguard the concurrent data transmission, collision avoidance information is included in the control packets and used by the neighboring nodes to determine whether they should begin their transmissions. Also, to isolate the possible interference between DATA packets and ACK packets, a new ACK sequence mechanism is proposed. Simulation results show that a significant gain in throughput can be obtained by the CTMAC protocol compared with the existing work including the IEEE 802.11 MAC protocol. 相似文献
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一种用于无线自组织网络的并发传输MAC协议 总被引:1,自引:0,他引:1
本文提出一种工作在单信道、单发射器和单发射功率模式下的并发传输MAC协议.该协议在控制报文(RTS/CTS)和数据报文(DADA/ACK)之间插入附加控制时隙,以便相邻节点有机会交换自己的控制报文.为了保证并发传输的可靠性,协议在控制报文中包含了冲突避免信息,邻居节点根据这些信息判断自己的传输能否在不影响已有传输的情况下并发进行.模拟结果显示,与IEEE 802.11相比,CTMAC协议在网络中存在并发可能时,使系统吞吐量得到很大提高. 相似文献
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Maciej Jan Zawodniok Sarangapani Jagannathan 《International Journal of Wireless Information Networks》2007,14(4):251-263
In this paper, two novel energy-efficient rate adaptation schemes are presented. The proposed protocols use the Distributed
Power Control (DPC) algorithm to predict the channel state and determine the necessary transmission power which optimizes
the energy consumption. The first proposed rate adaptation scheme heuristically alters the modulation rate to balance the
energy-efficiency and the required throughput which is estimated with queue fill ratio. Moreover, the back-off scheme is incorporated
to mitigate congestion and reduce packet losses due to buffer overflows thus minimizing energy consumption. Consequently,
the nodes will conserve energy when the traffic is low, offer higher throughput when needed and save energy during congestion
by limiting transmission rates. The second rate adaptation scheme employs dynamic programming (DP) principle to analytically
select modulation rate and a burst size to be used during transmission. The proposed quadratic cost-function minimizes the
energy consumption while alleviating network congestions and buffer overflows. The proposed DP solution renders a Riccati
equation ultimately providing an optimal rate selection. The simulation results indicate that an increase in throughput by
96% and energy-efficiency by 131% is observed when compared to other available protocols, for example Receiver Based AutoRate
(RBAR).
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Sarangapani JagannathanEmail: |
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Token-passing medium access control (MAC) protocols are gaining interest among wireless ad hoc network researchers as they provide unrivaled advantages over the existing IEEE 802.11 standards. This paper introduces a hybrid token-code division multiple access (CDMA) MAC protocol that is based on a token-passing scheme with the incorporation of CDMA. With its unique CDMA feature, the proposed MAC is able to support multiple simultaneous transmissions. The proposed protocol provides both quality of service (QoS) and high network resource utilization while ensuring the stability of the network. This paper examines the performance of the proposed MAC scheme by simulation and compares its performance against that of other MAC protocols that have appeared in the literature. Simulation results demonstrate that our proposed MAC scheme is effective in decreasing the packet delay and significantly shortens the length of the queue. The input traffic model used in the simulation is a two-state Markov-Modulated Poisson Process (MMPP). The data rate QoS is enforced by implementing a modified leaky bucket mechanism in the proposed MAC scheme. The simulation also takes into account channel link errors caused by the wireless link by implementing a multilayered Gilbert-Elliot model. 相似文献