移动P2P文件共享系统中基于用户偏好的激励机制

提出一种基于用户偏好的激励机制,鼓励用户通过提供共享文件和转发操作为系统做出贡献。IMBPC结合了虚拟价格机制和预期文件传输延时,基于用户对价格和延时的偏好度来选择最合适的节点进行文件下载。通过设置模拟实同仅通过虚拟价格机制来激励用户做出贡献的策略进行比较,显示应用IMBPC策略的系统,节点的贡献积极性明显增加。     

无线自组网中TCP按需确认机制

分析无线自组网中关于传输控制协议(TCP)的问题,研究基于按需确认的TCP协议在无线自组网中的改进算法。该算法规定接收方须根据发送方的要求对数据报文进行确认,减少确认(ACK)数量并消除延迟ACK对TCP传输效率的影响,提高了无线自组网中TCP的性能。仿真试验结果证明了该算法的有效性。     

大规模农田传感器网络通信能耗模型

将无线传感器网络应用于农业中,构成农田监控网络,是实现农业信息化、自动化、智能化的重要手段.然而,农田无线传感器网络具有超大规模、超低成本、拓扑变化复杂等特点,这些特征对网络通信设计提出了更加苛刻的要求.从Heinzelman的无线传输能量模型出发,建立了一个适用于大规模农田传感器网络的通信能耗模型,该能量模型考虑了部署间距、传输半径以及数据包大小对系统总能耗的影响,获得了在传输间距z确定情况下,求最佳传输半径R的计算方法.同时,仿真分析了不同部署半径、不同网络规模对全网查询能耗的影响.     

基于随机模型的艾滋病预防与控制策略研究

建立了艾滋病传播过程中感染者人数占总人口比例所满足的随机模型,分析了环境因素对艾滋病传播过程的影响,利用数值解方法对模型进行分析,结合我国数十年间艾滋病病毒感染者实际数据进行仿真,验证模型的有效性;并对未来我国艾滋病病毒感染者人数占总人口比例进行预测,通过对其中的传染率控制指标β进行分析,得出这一指标的波动对艾滋病流行趋势的影响.通过分析其均值与方差,提出对β的调整策略以达到一定的控制目标,从而为艾滋病的预防和控制提供一定程度上的决策支持.     

基于ARM平台的嵌入式RTL8019AS网卡芯片数据通信的设计与实现

采用了基于ARM内核的微处理器S3C44BOX及RTL8019AS芯片来设计一个嵌入式以太网系统,包括10 Mbit/s以太网控制芯片RTL8019AS的接口电路设计,以及系统电路的调试,并在此基础上完成了在S3C44B0X单片机控制下的KTL8019以太网驱动程序设计,以及数据通信的软件实现方法.     

正交多载波降噪差分混沌键控通信系统

为解决多载波差分混沌移位键控(MC-DCSK)系统传输速率低和误码性能差的缺点,该文提出一种正交多载波降噪差分混沌移位键控(QMC-NR-DCSK)系统。在发送端,预定义载波用于发送参考信号,剩余M-1个不同中心频率的载波及其经正交调制技术后得到的频率相同但相位正交的载波都用于传输信息信号,此外,通过进一步引入Hilbert变换,将系统的频带利用率和传输速率提升为MC-DCSK系统的4倍。在接收端引入滑动平均滤波器的降噪操作降低了噪声的方差,从而改善了系统误码性能。推导了QMC-NR-DCSK系统在加性高斯白噪声(AWGN)信道和多径瑞利衰落(RFC)信道下的比特误码率公式并进行了仿真。仿真结果和理论分析表明：QMC-NR-DCSK系统能有效提升传输速率、带宽效率和误码性能,为该系统应用于多载波无线通信提供理论参考。     

Engineering TCP transmission and retransmission mechanisms for wireless networks

Transmission Control Protocol (TCP) provides mechanisms for reliable data communications. Although it works well in wired networks, it fails to offer satisfactory performance in lossy and wireless environments. And in the multi-hop wireless infrastructure, packet delivery suffers high cumulative loss rate if traveling over multiple wireless hops. The Selective acknowledgment (SACK) is one header option that might be used to combat segment corruptions in air channels. In this paper, an alternative set of flow control mechanisms is proposed to handle high packet loss rate in a wireless medium. Using a measurement-based mechanism, sustainable segment delivery is achievable through a novel size-reduction method. Multiple segment retransmission mechanisms are introduced to reduce successive timeout events. One single byte loss is sufficient to waste all other bytes in a file received at a destination. That is, a good TCP flow control mechanism should provide a high successful file transmission completion rate, and this is set as our design goal. Through thorough simulations, our proposed multi-segment retransmission designs perform with higher successful file transfer rate and fewer timeout events than NewReno and SACK under a wide range of packet loss probabilities.     

Multi-sector multi-range control for self-organizing wireless networks

In this paper, we propose a distributed multi-sector multi-range (MSMR) control algorithm for supporting self-organizing wireless networks. The algorithm enables us to reduce the unnecessary coverage with fine-tuned range control and also to increase the network-wide capacity with enhanced spatial reusability. The proposed algorithm discovers neighboring nodes within the maximum transmission range at every node, divides its transmission area into multiple non-overlapping angular sectors of a given degree, chooses the home sector for each neighboring node according to its relative position, and constructs a spanning subgraph per sector by determining appropriate transmission range to maintain connectivity. Since the range control influences on network connectivity directly, we prove in the first place that the proposed algorithm preserves both network-wide and local connectivity as far as both connectivity exist in the network that uses the maximum transmission range. In order to investigate the performance of the proposed algorithm, we implemented it in the ns-2 simulator, and performed an extensive set of simulation study in comparison with other transmission range control schemes. The simulation results indicate that the proposed scheme is superior to other schemes with respect to the network-wide throughput and its normalized value per energy in various simulation configurations. In specific, the algorithm achieves minimally one order and maximally two orders of magnitude improvement in those performance evaluations. The improvement becomes more salient as the number of nodes increases and is immune to traffic type, network size, node distribution, or node density.     

改进的TCP/RED模型的稳定性分析

TCP自同步特性可提高网络稳定性,TCP/RED拥塞控制模型忽略了TCP自同步特性。针对该问题,提出包含TCP自同步特性更接近实际网络的改进TCP/RED拥塞控制模型。应用Nyquist稳定性判据给出当改进模型在复平面上属于某一不包含-1+j0点的下半平面时的稳定性条件,得到比TCP/RED模型更宽松的RED参数设置范围。NS2仿真验证了该稳定性条件的有效性。     

改进的无线网络TCP协议跨层设计方法

针对传统TCP协议的拥塞控制机制在无线网络中不能很好地解决数据丢失的问题,提出一种改进的无线网络TCP协议跨层设计方法——NTCP。NTCP将传统TCP功能分割为传输速率控制和数据完整性控制2个部分,避免使用转发节点信息的方法,最大限度地利用无线资源。该方法与传统TCP-Reno方法相比,能提高无线网络的吞吐量,其稳定性和速率自适应能力也有较好的改善。