基于多种调制结合的比特重排混合ARQ方法

提出了一种适用于QAM调制的混合ARQ(HARQ)方法,该方法将比特重排和不同的调制等级结合,重传时可以选择更多的重排方式,并且重传的比特数与调制等级相对应,与已有的基于同种调制的比特重排方法相比,新方法在降低复杂度的同时能够进一步提高HARQ的性能。     

无线传感器网络中数据可靠传输策略的研究

针对无线传感器网络的特点,提出了一种可保证数据可靠传输策略和相关的路由算法.当在数据传输过程中中间节点出现故障时,该策略能利用ARQ机制检测是否有数据包丢失,并采用hop-by-hop机制进行重传处理.理论分析表明,该策略能有效提高网络中数据的可靠传输,节约网络功耗,有效延长网络寿命.     

基于类别的加权公平排队的帧中继流量整形

基于类别的加权公平排队的帧中继流量整形可以有效地控制网络流量,保证特殊通信流类别的带宽和实时传输,避免过多的数据包因发送失败同时进行重传而引起更严重的资源紧张,进而提高网络的总体流量,本文对此作出阐述并给出配置实例。     

IEEE 802.16e协议ARQ部分的仿真研究

主要仿真实现了IEEE 802,16e协议MAC层的自动请求重传部分。完成了ARQ程序编写和调试,主要包含数据发送、数据接收、ACK发送以及ACK接收四个部分。此外还完成了ARQ的初始设置函数以及block生命周期定时器、重传定时器以及ARQ同步丢失定时器。并搭建了接收窗口重置定时器以及ACK周期回复定时器的框架,为进一步的改进提供了基础。     

无线传感器网络中数据可靠传输策略的研究

针对无线传感器网络的特点,提出了一种可保证数据可靠传输策略和相关的路由算法。当在数据传输过程中中间节点出现故障时,该策略能利用ARQ机制检测是否有数据包丢失,并采用hop-by-hop机制进行重传处理。理论分析表明,该策略能有效提高网络中数据的可靠传输,节约网络功耗,有效延长网络寿命。     

.NET下不连续异步消息处理的研究

针对服务器端与嵌入式客户端之间通过GPRS通信存在连接不连续性的问题,研究了一种基于.NET框架下的异步消息处理机制,并利用这种机制提出了一种在网络通信连接不连续情况下实现消息异步处理的解决方案。最后将这种方案应用到实际项目中,验证了这种方案可保证数据的可靠传送和一次传输成功,从而提高了系统的吞吐量和稳定性,同时优化了系统的性能。     

QoS优化筛选认知系统频谱资源差错控制

无线电认知系统频谱资源差错控制是决定无线电传输和通信质量优劣的关键。传统的无功率控制方法由于需要使用授权用户的先验信息,出现无线电频谱资源规模集群和感知预留,通信过程中,出现丢包率高和堵塞,频谱感知差错控制效率低下。考虑无线信道的时变特性,采用QoS优化筛选控制的方法,提出一种基于协作用户频谱感知模型的无线电认知系统频谱资源差错控制方法,采用CS.MA/CA信道访问MAC协议进行信道建模,得到QoS控制过程的时间线。基于能量检测K/N判决准则,建立无线电频谱感知差错控制判决模型。实验结果表明,采用该方法进行无线电认知系统频谱资源差错控制,频谱感知网络负载降低,传输时延减少,提高了资源包的接收率。     

无线多点智能报警系统的设计

本文设计一个智能报警系统,将短距离无线传输与GSM远程通信相结合,实现多个房间的远程报警。当监控场所发生紧急情况(盗窃、气体泄漏等)时,通过无线传输模块向主机发送报警信号。主机现场发出声光报警,并通过GSM向户主发送短信息实现远程报警。当有多个房间报警时,在用户短信息中能显示出报警的房间号和报警类型。     

修正的HARQ加密方案第三方支付系统安全设计

引入云计算的虚拟化技术,提出一种修正的HARQ加密方案,利用群签名和椭圆曲线算法ECC提高加密协议的执行效率,根据上行CSI信息对重传分组自适应地选择冗余版本数,结合云计算的虚拟化技术建立一种基于修正的HARQ加密方案的可信云平台第三方支付方案,嵌入设计到第三方支付系统中,最后对方案的安全性和效率进行分析。仿真实验表明,采用该算法进行第三方支付信息加密和支付系统嵌入设计,能够提供安全稳定的隐私保护和远程证明,支付平台通信效率提高,安全保护性较强。能有效促进电子商务产业的安全发展。     

基于GPRS的远程抄表系统

本文提出了一种基于GPRS通信技术的电力远程抄表系统,该方案利用GPRS的Internet接入功能,在Internet上设置通信服务器,负责客户端服务器与GPRS终端设备之间的通信,实现数据的实时采集和传输。详细介绍了系统的构成和工作原理,该系统具有传输速率高,数据吞吐量大,通信实时,可靠等优点。     

Control of connected vehicles with event-triggered transmission and prescribed energy budget

This paper is concerned with event-triggered cooperative control of a platoon of connected vehicles via vehicular ad hoc networks (VANETs). To reduce communications among vehicles, we introduce a hybrid event-triggered transmission mechanism based on both time elapsed and state error. The effect of time-varying transmission delay and communication energy constraint can be also taken into account in the system modeling and design procedures. The on-board sensors use different power levels to transmit information resulting in different packet loss rates. The vehicular platoon system is proved to be exponentially mean-square stable under the hybrid event-triggering scheme and a constant time headway spacing policy. A framework for co-design of the hybrid event triggering scheme and the output feedback controller is given to guarantee platoon stability and spacing-error convergence along the stream. Numerical simulations are given to demonstrate the effectiveness of proposed method.     

A flow and routing control policy for communication networks with multiple competitive users

This paper is concerned with deriving an optimal flow and routing control policy for two-node parallel link communication networks with multiple competing users. The model assumes that each user has a flow demand which needs to be optimally selected and routed on the network links. The flow and routing control policy for each user seeks to maximize the user's total throughput and minimize its expected delay. To derive such a policy, we consider a utility function for each user that combines these two objectives in an additive fashion with preference constants that can be adjusted to reflect the user's own preferences between maximizing throughput and minimizing delay. Additionally, we provide each user with the ability to make these preferences link-dependent to reflect the user's preferences for certain links over others in the network. A condition that depends on the link capacities and preference constants is derived to guarantee the existence and uniqueness of a non-symmetric flow and routing control policy solution which satisfies the Nash equilibrium of non-cooperative game theory. The Nash equilibrium is a desirable solution for such networks because it insures that no user can improve its utility by unilaterally deviating from its Nash control policy. We discuss in detail several interesting properties of this equilibrium and in particular, its relationship to the users’ preference constants. Two illustrative examples are also presented.     

GEO卫星通信中空时协同性能分析

GEO卫星通信的用户下行链路为典型的衰落信道,经卫星转发的信号如果经历大尺度衰落,则用户端接收到的信号将产生大范围失真。该文针对GEO卫星通信的特点,为了提高GEO卫星系统的通信性能,考虑将空时协同技术引入到GEO卫星通信中。并仿真分析了在不同信道环境下,使用不同分集方案时GEO卫星通信系统性能,结果显示使用空时协同技术后,系统的可靠性有明显提高。     

无线传感器网络的分布式用户认证机制

本文针对无线传感器网络的用户认证问题给出了一套分布式的认证方案。此方案利用自我验证密码系统（self-certified key cryptosystems）来建立对等密钥,在对等密钥建立的基础上给出了两种不同类型的认证：本地认证和远端认证。我们的认证方案不但具有很强的安全性,而且由于具有较低的通信与计算代价,从而很容易在传感器网络中实现。     

WiMAX Mesh网络下具有QoS保障的动态握手方案

WiMAX Mesh网络中的3步握手时间影响数据包的延迟和带宽请求次数.固定3步握手参数会给网络带来扩展性问题,且不利于满足用户不同的QoS需求.针对上述问题提出具有QoS保障的动态握手参数调整方案QoSDx,综合节点自身和2跳邻居节点的数量、优先级和3步握手参数等动态调整节点的握手时间.仿真实验表明,QoSDx在不同规模网络下均能提高网络总体性能.IEEE 802.16标准中定义的4种业务流的吞吐率平均提升10%左右.     

Destination buffer analysis for packets rejection obliteration in multi-channel networks

In this paper we study a multi-channel network, each station of which is equipped with a network interface that has a receiver buffer of multiple packets. In this way, each station is able to receive multiple packets per time instant. We adopt a synchronous access protocol which is affected by the collisions over the multiple channels and the destination conflicts. The proposed protocol performance crucially depends on the size of the receiver buffer since it determines the packet rejection probability at destination. An analytical probabilistic model based on a Markovian process is adopted for the performance measures derivation by means of closed mathematical formulas. The proposed protocol is compared to relative ones that either totally ignore the receiver collisions or assume a receiver buffer of a single packet capacity. The numerical results show that the increase of the receiver buffer size improves the performance decisively, resulting in higher throughput and lower delay and rejection probability. Also, it is shown that the appropriate receiver buffer size per station in order for the rejections at destination to be effectively eliminated is not unlimited but is limited to three packets for 0.1% accepted maximum level of rejection probability.     

网络排队策略优化的OPNET仿真研究

移动通信技术的迅速发展,越来越需要各种网络技术的全面支持与融合。基于这个原因,就路由器传递数据包的排队策略对移动通讯系统的服务质量进行了研究,并利用OPNET软件进行了仿真。结果表明,采用wFQ策略,接口每次按不同的权重从不同队列中取不同数量的数据包发送,能优化路由器的数据吞吐量。     

A cognitive TV white space-broadband power line MIMO system for indoor communication networks

Broadband power line communication (BPLC) is a promising solution to satisfy the growing data rate demands for broadband indoor communication networks. However, the BPLC transmission power spectral density (PSD) is restricted in the very high frequency (VHF) band to avoid harmful interference to the existing wireless services. In this paper, a new hybrid system is proposed utilizing BPLC and cognitive radio over TV white space (TVWS) to enhance the system capacity over BPLC in VHF, forming a VHF TVWS BPLC multiple-input multiple-output (MIMO) system. An iterative precoding algorithm is proposed to satisfy the interference limit at the TV primary user (PU) receiver (Rx) and enhance the ergodic capacity. Moreover, a power allocation algorithm is developed for the MIMO system to achieve the maximum ergodic capacity subject to the average total power constraint and limit of interference to TV PU. Simulation results demonstrate the significant enhancement in the achieved capacity by our proposed system in the VHF band compared to both previous cognitive and hybrid BPLC systems.     

Robust cooperative output regulation of heterogeneous uncertain linear multi-agent systems by intermittent communication

In this paper, we study the robust cooperative output regulation problem of heterogeneous linear multi-agent systems with system uncertainties and directed communication topology. A robust distributed event-triggered control scheme is proposed based on the internal model principle. To avoid continuous monitoring of measurement errors for the event-triggering condition, a novel self-triggered control scheme is further proposed. Moreover, by introducing a fixed timer in the triggering mechanisms, Zeno behavior can be excluded for each agent. An example is finally provided to demonstrate the effectiveness of the proposed self-triggered control scheme.