自适应的Ad hoc MAC协议

为Adhoc网络提出了一种基于模糊逻辑的媒体接入控制层协议。该协议通过在MAC层采用模糊逻辑协调各个相互影响的数据流,为低优先级数据流选择附加退避窗口以减少其自身接入信道概率。通过这种方法,使得高优先级数据流在各种背景流量的条件下,均能够维持较高的端到端吞吐量和较低的端到端接入时延。仿真结果表明,该协议较802.11e协议更好地保护高优先级数据流的端到端时延和吞吐量。     

一种用于Ad hoc网络的优化拥塞控制算法

从分析Adhoc网络的信息流竞争特点出发,引入了链路干扰集的概念,构建了一个基于链路干扰集的价格框架。在此框架中,某链路的拥塞信息被表示为此链路干扰集的总价格。并提出了相应的分布式平行算法-价格协同法PCA来求解在小时间段内网络状态不变的拥塞控制问题。同时,分析了PCA对网络状态变化的自适应性能。仿真结果表明,PCA能快速收敛到全局优化解,对网络状态的变化有较好的自适应能力,所获得的网络性能比TCP-Reno要优越得多。     

无线移动自组网混合式密钥管理方案研究

基于门限机制的密钥管理方案能提供高的安全性,但认证成功率较低,可扩展性差;基于证书链的密钥管理方案适合自组网的特点,但其安全性仅取决于证书链中节点的信任度,不能满足高安全要求的应用环境。该文提出了门限机制和证书链信任值方法相结合的混合式密钥管理和认证方案,在增加少量通信量的情况下,方案提高了自组网的认证成功率和系统的安全性,较好地平衡了自组网的安全性和认证成功率,满足自组网应用的安全要求。     

Comment on An and Schorfheide's Bayesian Analysis of DSGE Models

An and Schorfheide's article provides an excellent review of Bayesian estimation of DSGE models. Rather than recapitulating the points already made in this article, my comment focuses on three aspects. It proposes a convergence measure to take account of serial correlation of MCMC draws, explains why the DSGE-VAR framework for policy analysis can be improved by avoiding the ad hoc identification assumption, and discusses an alternative structural approach to model misspecification.     

面向链路状态信息的路由算法LSDSR

提出一种WA mesh网络组网方式,将WALN技术与Ad hoc技术相结合,充分发挥二者的优势。针对WA mesh需要高性能路由算法,提出一种基于链路状态信息的改进路由算法LSDSR。分析表明WA mesh网络不仅具备WLAN网络成本低、吞吐量高、通信可靠的特点,还具备Ad hoc网络的高移动性、高灵活性、高抗毁性的特点。LSDSR路由算法能够减少路由中断的几率,减少网络中洪泛信息的出现,不仅改善了路由发现时间和链路负载,而且改善了路由请求信息和丢包率,提升了网络的效率,对链路的延迟、网络确认控制方面也有更良好的表现。     

Ad hoc网络中基于拥塞的机会调度算法

无线多跳Ad hoc网络中的节点在业务发送过程中需要竞争共享信道,容易发生局部拥塞导致网络性能下降,而且节点内部采用的先入先出(FIFO)队列容易使队头出现阻塞现象,影响队列中后续分组的发送。为此提出了一种基于拥塞的机会调度算法,发送节点发送RTS帧时目标指向多个下一跳接收节点,这些节点在正确解码RTS帧后根据自身拥塞程度按一定概率依照调度优先级顺序发送CTS帧。仿真结果表明,该算法提高了网络端到端的饱和吞吐量和信道利用率,也提高了业务流之间的公平性。     

一种基于IEEE 802.11 PSM的增强节能机制

分析了IEEE802.11分布式协调功能的能量节省机制,针对其采用一种固定信号时隙的局限性,提出了一种自适应节能机制。新机制采用三种信号时隙,由节点根据自己的数据流量动态选择其中一种。仿真结果表明,此机制在保持较高的吞吐量的同时,不仅大幅地提高了能量利用率,还明显地降低了时延。     

On an ad hoc test for order restricted multivariate normal means

Abstract

For several normal mean vectors restricted by a simple ordering with respect to a multivariate order, this article derives sufficient and necessary conditions for the restricted MLEs for both mean vectors and covariance matrix, and develops an ad hoc test. It establishes conditions for the bounds of the p-values. One example of such bound is given with some comments.     

Ad hoc网络稳定的蚁群多路由算法

针对Ad hoc网络路由协议中存在的路由老化和对拓扑变化适应性差的问题,提出了一种基于稳定拓扑和蚁群优化的多路由算法(SAMR),路径质量由路径的拓扑稳定度和时延来度量,并映射为蚁群信息素,利用蚁群优化进行路由的动态更新和维护,以避免路由老化。仿真表明,在动态环境下SAMR相比AODV能提高网络的吞吐量、降低传输时延。     

The Competitive Impact of Targeted Television Advertisements Using DVR Technology

Digital video recorders (DVRs) are an emerging technology that is fundamentally changing the competitive landscape in industries that advertise on television. Perhaps the most familiar impact of DVR technology is that it enables consumers to avoid advertisements (ads) by fast forwarding through them. However, this “zipping” of ads is only one aspect of the impact of DVR technology. DVRs also collect a wealth of information at the consumer level that can be used by firms to target their ads more effectively. We examine how this targeting capability moderates the impact of ad avoidance in a competitive setting. Insights are provided on how best to manage this emerging technology in terms of the key managerial decisions of product pricing and advertising efforts, as well as its impact on profits in a competitive (duopoly) marketplace.