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实现多个数据流对无线信道的公平共享是802.11无线Ad Hoc网络中的一个重要议题,但802.11DCF机制在无线Ad Hoc网络中存在严重的公平性问题,甚至有可能出现单个节点或数据流独占信道而其他节点和数据流处于"饥饿"状态的情况.论文提出了一种新颖的保证数据流间公平性的MAC层接入机制FFMA(Flow rate-based Fair Medium Access),通过公平调度和公平竞争的方式,FFMA能够在数据流间公平地分配信道带宽资源.仿真结果表明,在无线Ad Hoc网络中,FFMA可以在保证信道吞吐量的前提下取得远优于802.11 DCF的数据流间的公平性. 相似文献
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在射频供能无线传感器网络中,提高网络能效和吞吐率是一个重要的研究问题.该文统筹考虑信道分配、节点的能量阈值以及MAC(Medium Access Control)帧分块重传机制,提出高能效和高吞吐率的数据收集方案;推导了节点的充电时间、节点传输一个MAC帧的平均能耗和平均时延、网络能效和吞吐率,定义了网络效用函数,形成了最大化网络效用的优化问题.通过调整效用系数并求解优化问题,可以获得使网络能效和吞吐率最大化的最优能量阈值和MAC帧最优分块个数.仿真结果表明,所提方案的能效和吞吐率高于已有方案. 相似文献
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为了降低节点间广播消息产生的冲突,文中提出一种基于多跳路由的无线传感器网络环境中的公平性策略,使得簇内节点在向簇首转发数据包时,可以采用一种更为公平的方式竞争信道,各层节点根据自己的权值大小获得发送数据包权限后在下一轮进入休眠状态,在保证公平性的同时有效节省监听时耗费的能量,达到提高网络生命周期的目的. 相似文献
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缓存辅助多天线中继技术可以为5G通信系统提供广域覆盖范围,并且有效改善系统的吞吐率性能.研究了一个三节点多天线缓存辅助中继系统,提出了最大化系统平均吞吐率的最佳缓存辅助中继策略,即联合自适应链路选择以及功率分配方案.分析结果表明,最佳的链路选择方案仅依赖于当前的瞬时信道状态信息以及相关链路的信道统计信息,而最佳功率分配方案是对发送的数据流进行等功率分配.仿真结果表明,相对于无缓存辅助的MIMO中继系统,缓存的引入能够显著改善中继系统的吞吐率.此外,MIMO技术的引入还能够获得多天线所带来的复用增益,进一步改善缓存辅助中继系统的吞吐率. 相似文献
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提出802.11s草案中公共信道框架(CCF)多信道机制的性能分析模型和方法.确定CCF存在着分配和不分配公共信道传输数据2种状态,在公共信道上分别提出2种状态的性能分析模型并推导吞吐率计算公式,同时提出CCF的状态转移条件;以信道速率、数据帧有效载荷、信道数和站点数为参数对CCF的吞吐率和信道平均吞吐率进行仿真.仿真结果显示随着信道速率的增加、站点数的增多和/或数据帧有效载荷的减少,CCF由分配公共信道转移为不分配公共信道传输数据状态所占用的信道数量减少,CCF处于不分配公共信道传输数据状态时吞吐率最大. 相似文献
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Joshi T. Mukherjee A. Younghwan Yoo Agrawal D.P. 《Mobile Computing, IEEE Transactions on》2008,7(4):513-527
Under a multirate network scenario, the IEEE 802.11 DCF MAC fails to provide airtime fairness for all competing stations since the protocol is designed for ensuring max-min throughput fairness. As such, the maximum achievable throughput by any station gets bounded by the slowest transmitting peer. In this paper, we present an analytical model to study the delay and throughput characteristics of such networks so that the rate anomaly problem of IEEE DCF multirate networks could be mitigated. We call our proposal time fair CSMA (TFCSMA) which utilizes an interesting baseline property for estimating a target throughput for each competing station so that its minimum contention window could be adjusted in a distributed manner. As opposed to the previous work in this area, TFCSMA is ideally suited for practical scenarios where stations frequently adapt their data rates to changing channel conditions. In addition, TFCSMA also accounts for packet errors due to the time varying properties of the wireless channel. We thoroughly compare the performance of our proposed protocol with IEEE 802.11 and other existing protocols under different network scenarios and traffic conditions. Our comprehensive simulations validate the efficacy of our method toward providing high throughput and time fair channel allocation. 相似文献
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Kaikai Chi Yi-hua Zhu Yongchao Wu Victor C. M. Leung 《Mobile Networks and Applications》2016,21(3):425-435
In IEEE 802.11 infrastructure wireless local area network (WLAN), the communication between any two nodes is relayed by an access point (AP), which becomes the bottleneck of WLAN and severely restricts the overall throughput. It is well known that network coding technique is able to greatly improve the throughput of wireless networks. But, the available coding schemes do not make full advantage of channel capacity due to the fact that they pick at most one packet from each data flow for coding and the picked packets may have a great difference in packet size, wasting some channel capacity. To remedy the problem, in this paper, we propose the coding scheme that combines multiple buffered packets in one flow into a larger packet for coding so that the packets participating in coding have close sizes. We formulate an integer programming problem to find the optimal packet coding, which is solved by an optimal algorithm with relative high time complexity together with a heuristic algorithm with relative low time complexity. Simulation results show that the proposed coding scheme is able to greatly improve the throughput of WLAN and the throughput gain increases with the growth of the number of coding flows. 相似文献
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针对物联网(IoT)通信的低延时需求,为了保证数据传输的灵活性,本文构建一种基于短包传输的无人机(UAV)通信网络。由于非正交多址接入(NOMA)技术能够增加可服务的地面用户数量,故将该技术应用到无人机短包通信(UAV-SPC)系统中可以解决多用户的安全传输问题。与正交多址(OMA)技术相比,NOMA可有效提高用户接入公平性和频谱利用率,因此被广泛用于下行链路的通信传输。为解决复杂的安全传输问题,首先证明在功率和译码错误率约束的条件下,分别存在最优的功率分配,数据传输包长和系统传输比特数使目标用户的平均安全吞吐量最大。在此基础上,通过本文所提算法得到安全传输问题的优化解。实验结果验证了该算法的稳定性和可行性。此外,与基准方案相比,本文所提方案可有效降低短包传输的通信时延,提高系统中目标用户的平均安全吞吐量。 相似文献
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Behdis Eslamnour S. Jagannathan Maciej J. Zawodniok 《International Journal of Wireless Information Networks》2011,18(4):295-308
Single-channel based wireless networks have limited bandwidth and throughput and the bandwidth utilization decreases with
increased number of users. To mitigate this problem, simultaneous transmission on multiple channels is considered as an option.
In this paper, we propose a distributed dynamic channel allocation scheme using adaptive learning automata for wireless networks
whose nodes are equipped with single-radio interfaces. The proposed scheme, Adaptive Pursuit learning automata runs periodically
on the nodes, and adaptively finds the suitable channel allocation in order to attain a desired performance. A novel performance
index, which takes into account the throughput and the energy consumption, is considered. The proposed learning scheme adapts
the probabilities of selecting each channel as a function of the error in the performance index at each step. The extensive
simulation results in static and mobile environments provide that the proposed channel allocation schemes in the multiple
channel wireless networks significantly improves the throughput, drop rate, energy consumption per packet and fairness index—compared
to the 802.11 single-channel, and 802.11 with randomly allocated multiple channels. Also, it was demonstrated that the Adaptive
Pursuit Reward-Only (PRO) scheme guarantees updating the probability of the channel selection for all the links—even the links
whose current channel allocations do not provide a satisfactory performance—thereby reducing the frequent channel switching
of the links that cannot achieve the desired performance. 相似文献
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In this letter, a heuristic channel allocation and scheduling scheme is proposed. By comparing the size of the alternative‐factor assessment, which is obtained by simple calculation, we can easily find the most appropriate channel for each user for overall throughput enhancement. Numerical results show that the downlink throughput of the proposed scheme is higher than that of proportional fairness and is almost the same as that of the maximum C/I scheme, while user fairness remains better than that of the maximum C/I scheme. 相似文献
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一种提高IEEE 802.11吞吐量和公平性的自适应优化算法 总被引:2,自引:0,他引:2
该文提出了一种针对IEEE 802.11 DCF网络增强其吞吐量和公平性性能的自适应优化算法,算法基于网络节点侦听信道得到的网络状态信息进行竞争发送的自适应调整以获得最优的网络性能,称之为CSCC(Channel Sensing Contention Control)算法。算法采用了对节点的信道接入请求以概率参数P_T进行过滤的方法控制节点竞争接入信道的激烈程度,其主要特点在于在优化调整过程中不需要进行计算复杂的网络节点数量估计,并且可以在不同网络状态下围绕始终确定的优化目标进行参数优化调整。仿真实验结果表明,算法能够适应不同节点数量和不同数据大小的网络进行自适应的网络优化调整,并获得了系统吞吐量、碰撞概率、延迟、延迟抖动、公平性等多方面的性能改善。 相似文献
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Adaptive Fair Subcarrier/Rate Allocation in Multirate OFDMA Networks: Radio Link Level Queuing Performance Analysis 总被引:2,自引:0,他引:2
This paper presents a semi-analytical methodology for radio link level performance analysis in a multirate "orthogonal frequency-division multiple-access" (OFDMA) network with adaptive fair rate allocation. Multirate transmission is assumed to be achieved through adaptive modulation, and fair rate allocation is based on the principle of generalized processor sharing to allocate the subcarriers adaptively among the users. The fair rate allocation problem is formulated as an optimization problem with the objective of maximizing system throughput while maintaining fairness (in terms of transmission rate) among the users. The "optimal" fair rate allocation is obtained by using the "Hungarian method." A heuristic-based approach, namely the "iterative approach," that is more implementation friendly is also presented. The throughput performance of the iterative fair rate allocation is observed to be as good as that of optimal fair rate allocation and is better than that of the static subcarrier allocation scheme. Also, the iterative fair allocation provides better fairness compared to that for each of the optimal and the static subcarrier allocation schemes. To this end, a queuing model is formulated to analyze radio link level performance measures such as packet dropping probability and packet transmission delay under the above rate allocation schemes. In this formulation, packet arrivals are modeled by the discrete Markov modulated Poisson process, which is flexible to model different types of traffic arrival patterns. The proposed framework for radio link level performance analysis of multirate OFDMA networks is validated by extensive simulations. Also, examples on the application of the proposed model for connection admission control and quality-of-service provisioning are illustrated 相似文献
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Wireless multi-carrier communication systems that use packet schedulers based on channel knowledge have been proved their performance. Proportional fairness scheduling (PFS), if used in these systems, promises an attractive trade-off between fairness among users and system throughput. In this paper, an analytical solution is presented for the PFS throughput. Then, a simple scheme is presented to reduce the feedback signaling of the PFS without a significant loss in performance. This reduced complexity PFS attempts to meet a trade-off between multi-user diversity gain, fairness among users and low rate feedback signaling. As shown by simulations, for a large number of users compared to the number of sub-channels, this scheme kept fairness among users while minimizing the feedback signaling. 相似文献
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High speed data transmission in wireless networks demands better radio resource management schemes. A fair packet scheduling
is proposed for downlinks of a cellular TD-CDMA system for delay-tolerant applications. It is based on the combined consideration
of channel conditions, required throughput and achieved average throughput. A system dependent parameter is introduced to
control the maximum achievable date rate as well as the degree of fairness. Through analysis and simulation, we study the
tradeoff between system throughout (i.e., efficiency) and individual throughput (i.e., fairness). The relative performance
between the proposed scheme and the traditional schemes is evaluated through simulation to confirm the analytical observations.
The sensitivity of the system tolerance factor towards efficiency and fairness is also investigated.
相似文献
Alagan AnpalaganEmail: |
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Wen-Tzu Chen 《Wireless Networks》2008,14(6):769-776
In this paper, we propose an effective medium access mechanism to enhance performance of the IEEE 802.11 distributed coordination
function (DCF). One of the primary issues of 802.11 is a contention-based medium access control (MAC) mechanism over a limited
medium, which is shared by many mobile users. In the original 802.11 DCF, the binary exponential backoff algorithm with specific
contention window size is employed to coordinate the competition for shared channel. Instead of binary exponential increase,
we adopt linear increase for the contention window that is determined according to the competing number of nodes. We also
assume that the access point can broadcast the number of mobile nodes to each station through management frames. An analytical
model is developed for the throughput performance of the wireless medium. Using simulation results from the NS2 simulator,
we show that our model can accurately predict the system saturation throughput, and can obtain better performance in terms
of throughput, fairness, and packet drop. 相似文献