共查询到18条相似文献,搜索用时 61 毫秒
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Cloud computing is always adopted to enhance the computing capability of mobile systems , especially when the mobile users prefer to use some computation intensive applications . Consequently, the distributed wireless relay infrastructure should be deployed to aid the traffic transmission. To further enhance the QoS provisioning goals of wireless cooperative network, this paper puts forward a multiobjective approach for distributed optimal relay selection, which takes Bit Error Rate (BER) and Secrecy Capacity (SC) into account simultaneously. Firstly, our proposal partitions the channel state into several levels according to the received signaltonoise ratio (SNR) and describes the timevarying Rayleigh fading channel characteristics by using first order finitestate Markov model. Secondly, we model the relay selection as Restless Multiarmed Bandit optimal solution problem with respect to the channel state and the state transition probability. Finally, simulation results demonstrate the efficiency of the proposed approach which outperforms the existing ones . 相似文献
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作为一种全新的信息获取和处理技术,无线多媒体传感器网络在军事、工业、商业、环保中具有广阔的应用前景.无线多媒体传感器网络感知媒体丰富、数据量大,处理任务复杂等显著特点,使其QoS保障问题的研究极具挑战性.本文就此问题,总结了无线多媒体传感器网络的QoS需求及其当前所面临的技术挑战.从MAC层、网络层、传输层、应用层、交叉层以及中间件六个方面,着重描述了无线多媒体传感器网络QoS保障的国内外研究进展.最后,分析了当前亟待解决的问题以及未来的研究趋势. 相似文献
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首先,简要回顾了无线Mesh网络的基本概况,分析了在无线Mesh网络中提供QoS保障的必要性和重要意义。然后,系统地介绍了无线Mesh网络的物理层、MAC层和路由层QoS保障技术以及跨层QoS设计技术的国内外研究现状,对其进行了细致而科学的分类。最后,给出了它们的研究难点和研究方向。 相似文献
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介绍了Ad Hoc网络中保障实时业务QoS要求的时间同步多址接入协议。该类协议以时分多址为基础,通过资源预留为实时业务预约固定的时隙,赋予实时业务接入信道的优先权,保证了实时业务的接入延时,延时抖动以及吞吐量等QoS指标,为Ad Hoc网络支持多媒体业务的接入奠定了基础。 相似文献
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随着无线通信技术和传感技术的迅速发展和应用,无线传感网络(WSN)也需要为各种应用提供相应的QoS保障。但是资源受限的传感节点、分布式结构和复杂的通信协议都为QoS支持带来了巨大挑战。本文首先说明了WSN中提供QoS保障的必要性,回顾了传统网络和Ad Hoc网络中的QoS支持技术。然后,归纳了WSN中的各种应用,并分析了这些应用的QoS要求。最后讨论了当前的研究工作并指出了今后的工作方向。 相似文献
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无线传感器网络中协作波束形成的能量有效性分析 总被引:1,自引:0,他引:1
分析了无线传感器网络中端到端误码率给定情况下协作波束形成的能量效率,给出了不同路径损耗因子和传输距离下的最优协作发射节点个数.首先,综合考虑发射能耗和电路能耗,给出了接近实际情况的系统能耗模型,并推导出系统能耗与误码率之间的近似闭式关系.然后,基于该近似模型,给出了不同路径损耗因子和传输距离下使系统能耗最小的优化协作发射节点个数.理论分析和仿真结果表明:在系统调制方式和误码率给定的情况下,存在着一个临界距离使协作波束形成比非协作传输和协作空时编码都更节能;而且在不同路径损耗因子和传输距离下,存在不同的最优协作发射节点个数使系统能耗最小. 相似文献
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无线传感器网络中增加协作传输及其能量效率研究 总被引:1,自引:0,他引:1
该文研究了无线传感器网络中增加协作传输及其能量效率,解决了何时协作和协作的能效两个关键问题。导出了直接传输与协作传输的能效表达式,讨论了主要参数对协作传输性能的影响。仿真结果表明:当通信距离大于门限距离时,增加协作传输的能效优于直接传输的能效;通过优化所选中继节点的位置或调制阶数可以提高能效。 相似文献
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面向认知无线电网络中能量高效协作感知任务需求,提出了面向单次协作感知过程的能量最小化节点选择问题EMNS和面向在线协作感知的能量高效节点选择问题OENS。证明了两问题均为NP-hard难题。针对EMNS问题,提出采用分枝定界算法BAB求最优解和贪婪节点选择算法GS求近似解。针对OENS问题,提出为每个节点引入考虑能量消耗负载均衡的动态权重系数,基于BAB和GS算法设计了启发式的在线节点选择算法OBAB、OGS1。仿真实验结果表明,提出的算法可显著增加网络完成的协作感知过程次数,可有效延长网络"生存期"。 相似文献
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Francesco Delli Priscoli Tiziano Inzerilli Luis Muñoz 《Wireless Personal Communications》2006,37(1-2):23-39
This paper deals with quality of service (QoS) provision in wireless IP networks. QoS provision is particularly challenging in wireless networks, where network resources are generally limited, variable over time and shared. In the design of possible measures to assure QoS one should consider that standardization is well established for the network layer Internet Protocol and for many underlying technologies of frequent use (e.g. IEEE 802.11, BLUETOOTH or HIPERLAN II). Therefore, as far as research on QoS is concerned, there is little room in both the IP and the link-layers for improved IP over wireless interfaces. In this paper we illustrate a solution in which an intermediate Wireless Adaptation Layer (WAL) is transparently interposed between the IP layer and specific link-layer technologies as a solution to provide QoS. The WAL addresses two main issues: (i) compensation for channel impairments in different platforms in order to enhance wireless channel reliability and (ii) implementation of traffic control and packet scheduling mechanisms to satisfy bandwidth and delay requirements, as well as to enforce a general principle of fairness among the IP associations contending for network resources and achieve optimal exploitation of transmission capacity. The WAL consists of a set of modules, each one in charge of a specific task, which can be enabled or disabled depending on the specific network environment. The novelty of the WAL approach is its capability of adapting itself to different wireless interfaces selecting performance enhancing modules for specific networks. This requires to modify the standard TCP/IP protocol stack by introducing an intermediate layer between the IP layer and the Data Link layer, with performance enhancement purposes. This paper focuses on two modules in particular, namely a traffic control module, which is in charge of performing congestion control and channel state dependent scheduling (CSD) packet scheduling, and a forward error correction (FEC) module, which compensates for channel impairments. This paper presents the proposed architecture provided with these modules and reports some measurements and simulations highlighting benefits resulting from the use of such modules. 相似文献
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Energy-Efficient Broadcast and Multicast Trees in Wireless Networks 总被引:10,自引:0,他引:10
Jeffrey E. Wieselthier Gam D. Nguyen Anthony Ephremides 《Mobile Networks and Applications》2002,7(6):481-492
The wireless networking environment presents formidable challenges to the study of broadcasting and multicasting problems. In this paper we focus on the problem of multicast tree construction, and we introduce and evaluate algorithms for tree construction in infrastructureless, all-wireless applications. The performance metric used to evaluate broadcast and multicast trees is energy-efficiency. We develop the Broadcast Incremental Power (BIP) algorithm, and adapt it to multicast operation by introducing the Multicast Incremental Power (MIP) algorithm. These algorithms exploit the broadcast nature of the wireless communication environment, and address the need for energy-efficient operation. We demonstrate that our algorithms provide better performance than algorithms that have been developed for the link-based, wired environment. 相似文献
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无线网状网已经成为无线宽带通信领域的研究热点,但是基于交换技术的无线网状网因为其将整个网络看作是一个IP子网而无法适用于大范围的覆盖。在无线链路中采用协作中继,可以提高无线链路的传输速率及传输可靠性。同时采用基于网络层路由技术的无线网状网技术,可以实现整个无线网状网的频谱效率提升和厂域覆盖。不过,由于标准化、关键技术研究以及产业化推进方面还存在许多问题,使得协作中继技术在无线网状网中的应用面临着巨大挑战。 相似文献
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Heterogeneous wireless network is an effective scheme to improve both the spectrum efficiency and energy efficiency of cellular system. However, interference limits the performance of such heterogeneous wireless network seriously. Hence cooperative decision making, i.e., cooperative transmission is necessary. In this paper, we develop an energy-efficient scheme for cooperative transmission in heterogeneous wireless networks with QoS constraint. Since too much signaling is needed for absolutely centralized cooperation, which is infeasible in practical system, partly cooperation is considered in this paper. We first formulate the problem as a two-stage Stackelberg game. In the first stage, an energy-efficient transmission scheme for macrocell users (MUE) is proposed based on the interference state of the MUEs. In the second stage, after obtaining the SINR and target SINR of the MUEs, the femtocell base stations update their beamformers and optimize the transmission power individually through a non-cooperative game, the existence and uniqueness of the Nash equilibrium is proved. Then an iterative algorithm is proposed to obtain the Stackelberg equilibrium. Simulation results show the performance gain of the proposed scheme. 相似文献
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Energy-efficient communications is crucial for wireless sensor networks (WSN) where energy consumption is constrained. The transmission and reception energy can be saved by applying network coding to many wireless communications systems. In this paper, we present a coded cooperation scheme which employs network coding to WSN. In the scheme, the partner node forwards the combination of the
source data and its own data instead of sending the source data alone. Afterward, both of the system block error rates (BLERs) and energy performance are evaluated. Experiment results show that the proposed scheme has higher energy efficiency. When Noise power spectral density is -171dBm/Hz, the energy consumption of the coded cooperation scheme is 81.1% lower than that of the single-path scheme, 43.9% lower than that of the cooperation scheme to reach the target average BLER of 10-2. When the channel condition is getting worse, the energy saving effect is more obvious. 相似文献
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Kwon Taekyoung Choi Yanghee Bisdikian Chatschik Naghshineh Mahmoud 《Wireless Networks》2003,9(1):51-59
Recently there is a growing interest in the adaptive multimedia networking where the bandwidth of an ongoing multimedia call can be dynamically adjusted. In the wireless/mobile multimedia networks using the adaptive framework, the existing QoS provisioning focused on the call blocking probability and the forced termination probability should be modified. We, therefore, redefine a QoS parameter – the cell overload probability – from the viewpoint of the adaptive multimedia networking. Then, we propose a distributed call admission control (CAC) algorithm that guarantees the upper bound of the cell overload probability. Also, a bandwidth adaptation algorithm which seeks to minimize the cell overload probability is also presented. Simulation experiments are carried out to verify the performance of the proposed CAC algorithm. Furthermore, the performance of the adaptive wireless/mobile network is compared to that of the existing non-adaptive wireless/mobile networks. As a further step in QoS provisioning, we propose another QoS parameter, the degradation period ratio, and discuss analytically how the CAC algorithm guarantees the upper bound of the degradation period ratio. 相似文献