CRSN中基于随机网络演算的拥塞控制协议QoS边界分析

为了保证认知无线电传感器网络(CRSN)的服务质量(QoS),需精确求解所采用协议的性能边界,为此提出了一种基于随机网络演算(SNC)的QoS性能边界分析方法.以CRSN中的和式增加积式减少(AIMD)拥塞控制机制为评估对象,以通信时延和数据积压为QoS性能指标.根据CR资源传感器的发送速率分布,利用基于矩量母函数(MGF)的随机网络演算推导出AIMD机制的时延和积压边界模型.实验结果表明,不同CRSN场景中的模型计算值都在理论边界范围之内,证明了该边界分析模型具有良好的性能.     

无线网络中最小延迟代价网络编码的研究

网络编码能极大地提高网络吞吐量和传输可靠性.编码机会易受到数据包数量不公平性的影响,提出一个具有最小延迟代价的网络编码方法（MDCNC）.首先找到一条固定路由并确定该路由所经过的每一节点的编码能力,然后根据数据流在不同节点处以及不同时隙的可编码情况,灵活地应用该延迟发送策略,以牺牲较小的端到端延迟时间换取更多的编码机会.仿真结果表明,MDCNC能够带来更多的编码机会,进而使网络拥有更高的吞吐量.     

无线网络编码增益感知的低时延路由协议

降低无线网络数据包传递时延对实时应用有重要的意义.该文提出了一种编码增益的计算方法和编码图的简化方法,并基于此提出了编码增益感知的路由协议CGAR(Coding Gain Aware Routing).CGAR利用网络编码增益和无线链路的期望传输次数ETX(Expected Transmission Count)计算传递一个来自新流的数据包所需要的时间,并以此为选路度量,旨在降低数据传递时延.仿真试验表明,CGAR的时延优于COPE和DCAR协议.     

志愿计算系统时延分析

志愿计算(Volunteer Computing)系统是一种分布式计算系统,它利用全球空闲计算资源实现海量科学计算.随着志愿计算的广泛应用,系统时延性能分析变得日益重要.现有文献主要通过仿真和实验观察其时延特性,并不能深入分析系统参数的影响.为此,提出了一种新的数学模型对志愿计算系统时延特性进行分析.志愿计算系统可以建模为一个变速率服务的单服务台排队系统.理论分析表明,系统的平均队长与服务速率方差之间存在单调递增的关系.因此,系统在服务速率方差趋于0和无穷大两个极端情况下的平均队长分别为系统平均队长的下界和上界,而在这两种极端情况下,可以通过对系统模型的简化求得系统的平均队长.仿真结果验证了该方法所求平均队长上下界的正确性和准确性.     

A Unified Architecture for the Design and Evaluation of Wireless Fair Queueing Algorithms

Fair queueing in the wireless domain poses significant challenges due to unique issues in the wireless channel such as location-dependent and bursty channel errors. In this paper, we present a wireless fair service model that captures the scheduling requirements of wireless scheduling algorithms, and present a unified wireless fair queueing architecture in which scheduling algorithms can be designed to achieve wireless fair service. We map seven recently proposed wireless fair scheduling algorithms to the unified architecture, and compare their properties through simulation and analysis. We conclude that some of these algorithms achieve the properties of wireless fair service including short-term and long-term fairness, short-term and long-term throughput bounds, and tight delay bounds for channel access.     

控制网络的确定性延迟演算理论研究

控制网络的服务质量参数,尤其是数据传输的延迟界限,对控制系统的分析和设计尤为重要.网络演算技术能够确定性的建立网络服务质量参数与网络资源之间的映射关系.针对控制网络的特殊性,拓展了网络演算理论,并结合常用的拓扑结构以及调度策略推导出了控制网络服务质量研究中必需的网络演算理论.     

High efficient multipacket decoding approach for network coding in wireless networks

To improve the performance of transmission by reducing the number of transmission and network overhead of wireless single-hop networks, this paper presents a high efficient multipacket decoding approach for network coding (EMDNC) in wireless networks according to the idea of encoding packets which cannot be decoded and are stored in buffer by receiving nodes, the lost packets can be recovered from these encoded packets. Compared with the network coding wireless broadcasting retransmission (NCWBR), EMDNC can improve the efficiency of decoding and reduce the number of retransmission and transmission delay. Simulation results reveal that EMDNC can effectively reduce the number of retransmission and network overhead.     

基于随机网络演算的无线多跳网延迟边界分析

端到端延迟作为无线多跳网QoS中最重要的参数之一,其边界分析的准确性直接影响到无线多跳网的QoS保障,而其中流量场景的复杂性导致了分析的难度大幅增加。在综合考虑了无线多跳网流量场景中存在流量直接传输,流量汇聚和流量分裂的特性后,该文运用3种流量算子对系统进行建模,并首次结合随机网络演算提出一种分析无线多跳网延迟边界的方法。仿真结果表明,理论边界可以准确地预测无线多跳网的延迟情况,且明显优于确定性延迟上界。     

网络编码中的侦听管理策略

 在基于机会式网络编码的的无线单播应用中,每个节点需要缓存一些数据包,用来对编码数据包进行解码,该缓存称作侦听缓存.本文针对\"X\"型拓扑分析了传统的基于先入先出的侦听管理策略,理论结果表明侦听缓存有限时吞吐量随侦听缓存的减小而迅速降低.为此,提出了一种基于尽力服务的侦听管理策略,提高了侦听缓存中数据包被用作解码的概率,进而提高了系统吞吐量.为减少无用数据包被缓存的概率,提出了一种基于历史信息的侦听管理策略,可有效减少干扰流对系统吞吐量的影响.     

Adaptive Call Admission Control for QoS/Revenue Optimization in CDMA Cellular Networks

In this paper, we show how online management of both quality of service (QoS) and provider revenue can be performed in CDMA cellular networks by adaptive control of system parameters to changing traffic conditions. The key contribution is the introduction of a novel call admission control and bandwidth degradation scheme for real-time traffic as well as the development of a Markov model for the admission controller. This Markov model incorporates important features of 3G cellular networks, such as CDMA intra- and inter-cell interference, different call priorities and soft handover. From the results of the Markov model the threshold for maximal call degradation is periodically adjusted according to the currently measured traffic in the radio access network. As a consequence, QoS and revenue measures can be optimized with respect to a predefined goal. To illustrate the effectiveness of the proposed QoS/revenue management approach, we present quantitative results for the Markov model and a comprehensive simulation study considering a half-day window of a daily usage pattern.     

分布式队列服务算法在无线网状网包调度中的应用

根据无线网状网的包调度特点,结合已有的差分队列服务算法和分布式贝尔曼-福特算法,将有线网络中的差分队列服务算法改进为分布式队列服务算法（DQS）,使之实用于无线网状网中多任务条件下实现系统的吞吐量最大化。仿真实验证明了DQS算法能有效地避免传统多径传输中的按“类”或 “流”来进行调度的缺陷,有效地减少了数据包的端到端延时和缓冲区需求,尤其是DQS算法的实际平均吞吐量性能有了很大的提高。     

Efficient Packet Scheduling Using Channel Adaptive Fair Queueing in Distributed Mobile Computing Systems

In a distributed mobile computing system, an efficient packet scheduling policy is a crucial component to achieve a high utilization of the precious bandwidth resources while satisfying users' QoS (quality of service) demands. An important class of scheduling techniques, namely, the wireless fair queueing algorithms, have been extensively studied recently. However, a major drawback in existing approaches is that the channel model is overly simplified – a two-state channel (good or bad) is assumed. While it is relatively easy to analyze the system using such a simple model, the algorithms so designed are of a limited applicability in a practical environment, in which the level of burst errors is time-varying and can be exploited by using channel adaptive coding and modulation techniques. In this paper, we first argue that the existing algorithms cannot cater for a more realistic channel model and the traditional notion of fairness is not suitable. We then propose a new notion of fairness, which bounds the actual throughput normalized by channel capacity of any two data connections. Using the new fairness definition, we propose a new fair queueing algorithm called CAFQ (Channel Adaptive Fair Queueing), which, as indicated in our numerical studies, outperforms other algorithms in terms of overall system throughput and fairness among error prone connections.     

无线mesh网中最小编码代价低时延多播路由

提出了一种无线mesh网中最小网络编码代价低时延多播路由协议(MNCLDMR, minimal network coding and low delay multicast routing)。MNCLDMR的目标是选择合适的网络编码节点,最小化网络编码代价,降低网络时延。MNCLDMR主要思想是引入拓扑关键节点和网络编码关键节点的概念,以下一跳的节点是否是网络编码关键节点或拓扑关键节点作为路由判据,采用MNCLD算法构造多播树。仿真结果表明,MNCLDMR可以达到预定目标,合理形成网络编码机会,能实现最小网络编码代价低时延多播路由。     

压缩用户缴费开机处理时长方案

客户因缴费后未及时开机的投诉一直居高不下.本文介绍了如何压缩用户缴费开机的处理时长,降低缴费类投诉.     

CDMA蜂窝移动通信系统中基于Eb/No的无线分组公平调度算法

在第三代移动通信的无线资源管理机制中,分组调度机制在保证预期的服务质量（QoS）和优化无线资源的利用率方面起到了至关重要的作用.至今已经有很多的调度算法被提出,用来有效地提高无线网络资源的利用率.本文提出一种基于Eb/No并且利用功率控制和管理机制的无线分组公平调度算法用来保证QoS,优化资源配置并且达到调度公平性.     

无线自组织网络的网络编码技术

网络编码作为一种新的技术在宽带无线自组织网络中有很好的应用,通过网络编码,中间节点可以将接收信息进行编码并发送出去,提高了网络吞吐量和健壮性。为不对现有网络的软硬件设备和相应的协议做很大的修改,可以选择在高层实现网络编码。无线传感器网络、无线格状网（Mesh）等无线自组织网络都可以使用网络编码技术显著提高多跳链路的传输性能。目前网络编码的研究热点集中在网络编码节点选取方案、网络编码算法的设计、网络编码复杂度分析、网络编码的性能分析、网络编码与系统安全性分析、网络编码在无线分布式网络中的应用等方面。     

基于网络编码的无线自组织网数据分发机制

 无线自组织网络中,移动台能量有限,为了延长生存期,需要减少中间节点之间的数据包交换次数,本文提出一种基于网络编码的数据分发机制CRNC,同基于泛洪的传统数据分发机制相比,CRNC在大幅度减少传输次数的同时,只增加了少量时延.理论分析及仿真试验,证明了采用网络编码的CRNC可以在传输时延和能量消耗上取得更好的均衡.