共查询到18条相似文献,搜索用时 265 毫秒
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战术瞄准网络技术系统作为美军新一代战术数据链系统,在链路层面以"全双工"通信为基础实现了基于优先级概率统计的多址接入协议SPMA(Statistic Priority-based Multiple Access)。战术数据链的链路层协议或称MAC协议描述了节点接入无线信道的规则,采用合适的MAC协议,能够更合理地分配有限的无线带宽资源,是战术数据链的关键技术之一。本文主要对统计优先级多址接入(SPMA)协议的信道占用状态进行研究,从物理层和网络层两方面对信道占用状态进行统计,然后采用预测技术有效的估计实际的信道占用状态,设计了一种准确的混合式信道负载统计方法,有效地降低了信道冲突,保证了数据发送的实时性和高优先级数据较高的成功传输概率。 相似文献
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针对航空Ad Hoc网络在高负载下的低时延信道接入问题,提出一种优先级与公平性协作的多信道MAC协议(PBLL/HL)。在多信道检测统计基础上加以改进,结合优先级机制,在高负载网络中适时截流低优先级业务,优化网络流量,保证高优先级业务低时延发送;设计公平性优先级阈值与冲突退避窗口算法(PCA),减小低优先级业务接入时延。仿真结果表明,PBLL/HL能够在高负载网络有效控制信道接入,维持良好的网络流量,降低网络平均接入时延(低优先级业务时延过载时降低10%以上),稳定高负载网络吞吐量(最大吞吐量88.1%,过载时吞吐量下滑平缓),解决了航空数据链高业务量带来的高时延和网络拥塞。 相似文献
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战术数据链(TDL)的作用就是在战场上能够更准确、有效和快速地传递战术情报。随着军事信息技术的发展,战场上的节点数量和传输数据呈现快速增长趋势。传统的战术数据链媒介访问控制(MAC)协议为了保证QoS,一般采用固定资源分配的多址访问算法,如TDMA,在面对大容量、高速率的需求时缺乏灵活性和有效性。为此,研究了基于统计优先级多址访问(SPMA)算法,提出了直接映射和差分趋势两种动态门限方法。仿真结果表明,动态门限比固定门限能够有效提高系统效率,更接近目标信道忙闲比设计,并且在相同负载下网络吞吐量也较固定门限高。 相似文献
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本文提出了一种新的、支持数据/话音业务并传的多址接入协议——根据用户数目妥善安排分组传输的多址接入(User-dependent Perfect-scheduling Multiple Access——UPMA)协议,它根据实际需求对上、下行带宽资源实行动态分配.UPMA协议对不同的业务类型赋予不同的优先级,并用轮询方式妥善地安排节点的分组传输;同时,它采用独特的帧结构,使话音业务总是能够得到优先传输.本文还提出了一种高效的竞争接入算法,以保证激活的节点能够快速接入信道.最后,对UPMA协议的性能进行了仿真并与MPRMA协议的性能进行了比较,结果证明UPMA协议有更好的性能. 相似文献
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该文提出了一种基于慢退避和实时优化思想的碰撞减少多址接入CRMA (Collision Reduced Multiple Access)协议。CRMA协议将实时优化的思想同慢退避的思想相结合,有效地解决了IEEE 802.11协议二进制指数退避算法成功发送数据帧后没有记录网络当前繁忙程度的缺点,能够更准确地记录数据帧成功发送后高负荷网络的退避阶数,降低数据帧接入信道的碰撞概率,提高无线信道的利用率。新的多址接入协议能够与现有的IEEE 802.11协议完全兼容,具有简单、无开销、完全分布性和自适应性的特点。分析和仿真结果表明,CRMA协议较之改进前的IEEE 802.11协议和其它最新的多址接入算法能够更有效地利用网络中已有的信息,更准确地估计网络当前的竞争状态,表现出更好的网络性能。 相似文献
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提出了一种新的PRMA改进协议。该改进协议可以同时支持语音和较高速率的数据业务,与MPRMA协议相比提高了系统吞吐量,降低了语音分组丢弃概率,适应移动多媒体业务的接入。 相似文献
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本文提出了基于有效竞争接入、高效无冲突传输的多址接入协议—UPMA+ +.该协议采用了有效的冲突分解策略和及时重获信道资源的方法,克服了UPMA(根据用户数目妥善安排传输的多址接入)协议中的开销;通过自适应调整竞争接入周期长度和限制无冲突服务周期长度的方法,很好地解决了激活节点快速接入信道和传输节点尽快传输分组之间的矛盾,从而提高了协议的吞吐量.本文还应用排队论的方法对UPMA+ +协议的性能进行了理论分析,计算结果与仿真结果基本一致. 相似文献
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Characteristics of Mobile Ad hoc Networks such as shared broadcast channel, bandwidth and battery power limitations, highly dynamic topology, and location dependent errors, make provisioning of quality of service (QoS) in such networks very difficult. The Medium Access Control (MAC) layer plays a very important role as far as QoS is concerned. The MAC layer is responsible for selecting the next packet to be transmitted and the timing of its transmission. We have proposed a new MAC layer protocol that includes a laxity-based priority scheduling scheme and an associated back-off scheme, for supporting time-sensitive traffic. In the proposed scheduling scheme, we select the next packet to be transmitted, based on its priority value which takes into consideration the uniform laxity budget of the packet, the current packet delivery ratio of the flow to which the packet belongs, and the packet delivery ratio desired by the user. The back-off mechanism devised by us grants a node access to the channel, based on the rank of its highest priority packet in comparison to other such packets queued at nodes in the neighborhood of the current node. We have studied the performance of our protocol that combines a packet scheduling scheme and a channel access scheme through simulation experiments, and the simulation results show that our protocol exhibits a significant improvement in packet delivery ratio under bounded end-to-end delay requirements, compared to the existing 802.11 DCF and the Distributed Priority Scheduling scheme proposed recently in [ACM Wireless Networks Journal 8 (5) (2002) 455–466; Proceedings of ACM MOBICOM '01, July 2001, pp. 200–209]. 相似文献
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In reservation-based multiple access protocols, before obtaining a contention-free access to the channel, a mobile terminal must wait for its request packet to be successfully sent to the base station. A pseudo-Bayesian ALOHA algorithm with multiple priorities is proposed in this paper to reduce the waiting time of delay sensitive request packets in a multimedia environment. Packets are transmitted in each slot according to a transmission probability based on the channel history and a priority parameter assigned to their respective priority class. An adaptation of the slotted protocol to the framed environment proposed for wireless ATM is also described. Simulation results are presented to show that the protocol offers a significant delay improvement for high priority packets with both Poisson and self-similar traffic while low priority packets only experience a slight performance degradation. 相似文献
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Afshin Fallahi Ekram Hossain 《Mobile Computing, IEEE Transactions on》2007,6(4):381-394
We present a novel queuing analytical framework for the performance evaluation of a distributed and energy-aware medium access control (MAC) protocol for wireless packet data networks with service differentiation. Specifically, we consider a node (both buffer-limited and energy-limited) in the network with two different types of traffic, namely, high-priority and low-priority traffic, and model the node as a MAP (Markovian arrival process)/PH (phase-type)/1/K nonpreemptive priority queue. The MAC layer in the node is modeled as a server and a vacation queuing model is used to model the sleep and wakeup mechanism of the server. We study standard exhaustive and number-limited exhaustive vacation models both in multiple vacation case. A setup time for the head-of-line packet in the queue is considered, which abstracts the contention and the back-off mechanism of the MAC protocol in the node. A nonideal wireless channel model is also considered, which enables us to investigate the effects of packet transmission errors on the performance behavior of the system. After obtaining the stationary distribution of the system using the matrix-geometric method, we study the performance indices, such as packet dropping probability, access delay, and queue length distribution, for high-priority packets as well as the energy saving factor at the node. Taking into account the bursty traffic arrival (modeled as MAP) and, therefore, the nonsaturation case for the queuing analysis of the MAC protocol, using phase-type distribution for both the service and the vacation processes, and combining the priority queuing model with the vacation queuing model make the analysis very general and comprehensive. Typical numerical results obtained from the analytical model are presented and validated by extensive simulations. Also, we show how the optimal MAC parameters can be obtained by using numerical optimization 相似文献
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G. RamMurthy G. Naveen Reddy A. Ravi Shankar Varma 《Wireless Personal Communications》2011,58(3):627-636
This paper proposes a medium access control (MAC) protocol for mobile Adhoc networks (MANET). The MAC layer is responsible
for selecting the next packet to be transmitted and the timing of its transmission. Various new factors are introduced to
determine the priority of the flow. The back-off mechanism devised by us grants node access to the channel based on the rank
of its highest priority packets. It is clear that the proposed algorithm works better than the existing distributed laxity
based priority-scheduling scheme and the same is proven using the simulation results using Glomosim. 相似文献
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车载网(VANETs)需提供时延敏感的安全应用和非安全应用的通信服务.这就使得媒体接入控制(MAC)协议既要满足安全消息的时延和可靠率,又要保证非安全消息的服务信道利用率,给MAC的设计提出了挑战.为此,提出基于时分多址的MAC改进算法(I-TDMA-MAC).I-TDMA-MAC算法在每个同步帧内给每辆车分配两个子时隙,旨在提高无碰撞信道接入率和安全消息的传递率.同时,对空闲时隙采取重分配策略,并基于最短作业优先准则(SJF)给空闲时隙设置优先级,旨在提高服务信道利用率.仿真结果表明,提出的I-TDMA-MAC算法的安全消息传递率高达99%,当车流密度到达100 vehicle/km时,服务信道利用率接近于90%. 相似文献
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Meejoung Aftab Soo-Won 《AEUE-International Journal of Electronics and Communications》2005,59(8):432-439
The algorithm of scheduling scheme of channel-aware priority-based groupwise transmission is investigated for non-real time data service for the uplink direct sequence code division multiple access (DS/CDMA) system using the burst-switching scheme to support the integrated voice/data service. The proposed scheme optimally determines the transmission-time groups and assigns optimal data rates to the users with packets in the transmission-time group depending on priority metric, which involves several parameters such as delay threshold, waiting time, length of packet, and state of the channel, in a way of minimizing the average transmission delay. Simulation results show that the proposed algorithm gives better performance of average transmission delay and packet loss probability than any other conventional algorithms. 相似文献
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解决突发包的冲突问题是光突发交换网络的关键技术之一。为了降低突发包冲突时丢包率,提出了一种新型的基于信道分级和回退机制的冲突解决算法,该算法考虑突发业务优先级,将信道分成两个级别,有区别地对待高低优先级两种业务类型,并且增加了一部分回退信道作为保护和重发冲突数据包,能够有效地保证高优先级业务的传输可靠性。结果表明,当冲突发生时,网络能根据此时高低优先级业务量的比重配比,自适应地调节两个级别信道的数量,兼顾到低优先级业务的低丢包率,保证了较低的延时率。此算法相比以往的冲突解决算法具有较低的丢包率和相对小的延时率。 相似文献