多跳Ad hoc网络TCP吞吐量模型

移动Adhoc网络是没有任何固定基础设施的移动无线网络。多跳特性是Adhoc网络区别于一般无线网络的最重要特点。详细分析了TCP性能随跳数变化的原因,并基于空间复用构造了一个简单的多跳Adhoc网络TCP吞吐量模型,用以计算不同跳数下的TCP吞吐量理论值。计算结果表明该模型与文献[1]的仿真结果吻合。     

多跳Ad hoc网络TCP吞吐量模型

移动Ad hoc网络是没有任何固定基础设施的移动无线网络.多跳特性是Ad hoc网络区别于一般无线网络的最重要特点.详细分析了TCP性能随跳数变化的原因,并基于空间复用构造了一个简单的多跳Ad hoc网络TCP吞吐量模型,用以计算不同跳数下的TCP吞吐量理论值.     

基于负载自适应的无线自组网视频传输队列调度算法

移动终端多媒体业务的发展目前已经成为终端发展的必然趋势.如何在移动终端构成Ad hoc网络时有效地进行视频传输是无线网络研究的热点之一.提出了一种基于负载状况的跨层优化方案,其基本思想是结合应用层视频编码的特点和接入层的网络负载和资源的情况联合进行优化.在特定的资源下通过概率接入的方法对重要性更高的数据包进行更优先的接入.仿真结果显示,在网络处于高负载、多跳传输等场景下,提出的方案视频传输质量PSNR值提升3 dB以上.相对于传统调度算法,系统时延也可以大幅度降低.     

虚拟链路精确流模型在AFDX网络演算中的应用

航空电子全双工交换式以太网(AFDX)是针对航空电子应用从工业交换式以太网升级而来的。其中,引入的虚拟链路(VL)和流量管制机制为网络通信任务提供了确定性的保障。网络演算是AFDX中常用的VL延时上界计算工具,为AFDX网络的实时性研究提供了理论依据。但是网络演算采用了VL简单流模型,计算得到的延时上界比较悲观。将VL精确流模型应用在网络演算工具中,并展示了基于精确流模型的网络演算能够得到更紧的延时上界计算结果。     

仿真研究无线多跳网络跨层协议设计的优劣

为了改善无线多跳网络的性能，很多研究表明跨层协议设计比OSI模型更适合无线网络。本文分析了无线多跳网络的特征及对各协议层的影响，给出了跨层协议设计对网络性能的改善以及它可能带来的问题，并针对速率自适应MAC协议和网络层路由协议之间的相互影响给出了仿真实例，结果证明跨层协议设计要充分考虑不同协议之间的相互影响，合理规划、谨慎实施，否则网络的性能不升反降。     

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.     

基于快速转发服务机制的端到端延时上界预测研究

以往运用确定性网络演算理论已经得到EF(Expedited Forwarding)流端到端延时上界表达式,它对实际网络的QoS控制起到了重要参考作用,但是这个表达式不够精确,而且只能描述网络状况最坏情况下的延时上界.本文改进了用确定性网络演算得到的EF流端到端延时上界,推导出更精确的延时上界表达式.同时,引入生灭模型,得到EF流端到端延时上界的概率分布表达式,能够描述不同网络状况下的延时上界.相比以往的结果,本文推导出的延时上界概率分布能够更准确地描述延时上界,具有更好的参考价值.     

5G移动网络下通信资源分配算法

传统的通信资源分配方法具有局限性,在当前5G移动网络条件下,通信过程中的信息传输速率不能满足通信频谱的资源利用率要求,为此,文章提出5G移动网络下通信资源分配算法。在研究边缘网络的基础上,建立5G移动网络的边缘计算模型,将数据传输端进行分层处理,包括计算云层、边缘层以及终端层三个层级,拉近云计算服务器与用户个体之间的数据传输距离。根据模型建立边缘计算的资源分配框架,计算无线链路的数据传输速率,避免陷入局部最优解。同时,将终端层用户进行分簇处理,避免数据传输过程中的同频干扰,提升资源分配效率。在此基础上,基于A3A算法构建簇间的通信资源分配模型,并使用最优化理论对所建立的资源分配算法模型进行优化,实现5G移动网络下通信资源分配算法设计。最后,通过实验对比传统D2D算法与设计的分配算法,结果表明,该算法能够适应5G移动网络环境,保证通信服务过程中信息传输速率的稳定,能够实现通信资源的高效分配。     

基于随机网络演算的车联网边缘计算多跳任务卸载性能分析

车联网(IoV)边缘计算通过在网络边缘部署计算资源，可为车载用户提供低时延服务。该文通过随机网络演算(SNC)矩母函数(MGF)法分析车联网移动边缘计算的时延和数据积压性能。首先，分别对车辆高优先级和低优先级业务到达过程、单跳毫米波通信服务过程和边缘计算服务过程进行数学建模；其次，由服务级联定理获得不同优先级业务在多跳网络中的服务过程及其矩母函数表达式；接着，推导了车辆边缘网络不同优先级业务毫米波多跳通信任务卸载的时延和数据积压概率边界闭式解；最后通过蒙特卡罗仿真验证闭式解的准确性。     

面向M2M通信的移动网络拥塞控制

研究表明,M2M通信具有潜在的市场前景,海量终端接入使得移动网络面临着网络拥塞的问题。本文首先分析了移动网络拥塞产生的场景,在此基础上按照核心网络、终端和无线网络分别描述了不同层面的解决方案。其中核心网络的解决方案包括拥塞识别、接入拒绝方法;终端设置低优先级说明了低优先级是与应用相关的;无线网络的解决方案包括拥塞控制触...     

Energy–delay tradeoff in wireless multihop networks with unreliable links

Energy efficiency and transmission delay are very important parameters for wireless multihop networks. Numerous works that study energy efficiency and delay are based on the assumption of reliable links. However, the unreliability of channels is inevitable in wireless multihop networks. In addition, most of works focus on self-organization protocol design while keeping non-protocol system parameters fixed. While, very few works reveal the relationship between the network performance and these physical parameters, in other words, the best networks performance could be obtained by the physical parameters. This paper investigates the tradeoff between the energy consumption and the latency of communications in a wireless multihop network using a realistic unreliable link model. It provides a closed-form expression of the lower bound of the energy–delay tradeoff and of energy efficiency for different channel models (additive white Gaussian noise, Rayleigh fast fading and Rayleigh block-fading) in a linear network. These analytical results are also verified in 2-dimensional Poisson networks using simulations. The closed-form expression provides a framework to evaluate the energy–delay performance and to optimize the parameters in physical layer, MAC layer and routing layer from the viewpoint of cross-layer design during the planning phase of a network.     

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.     

Cross-layer resource allocation over wireless relay networks for quality of service provisioning

The authors propose a physical-datalink cross-layer resource allocation scheme over wireless relay networks for quality-of-service (QoS) guarantees. By integrating information theory with the concept of effective capacity, the proposed scheme aims at maximizing the relay network throughput subject to a given delay QoS constraint. This delay constraint is characterized by the so-called QoS exponent thetas, which is the only requested information exchanged between the physical layer and the datalink layer in our cross-layer design based scheme. Over both amplify-and-forwards (AF) and decode-and-forward (DF) relay networks; the authors develop the associated dynamic resource allocation algorithms for wireless multimedia communications. Over DF relay network, the authors also study a fixed power allocation scheme to provide QoS guarantees. The simulations and numerical results verify that our proposed cross-layer resource allocation can efficiently support diverse QoS requirements over wireless relay networks. Both AF and DF relays show significant superiorities over direct transmissions when the delay QoS constraints are stringent. On the other hand, the results demonstrate the importance of deploying the dynamic resource allocation for stringent delay QoS guarantees.     

Data-flow in mobile edge computing networks: end-to-end performance analysis using stochastic network calculus

Mobile edge computing (MEC) networks can provide a variety of services for different applications. End-to-end performance analysis of these services serves as a benchmark for the efficient planning of network resource allocation and routing strategies. In this paper, a performance analysis framework is proposed for the end-to-end data-flows in MEC networks based on stochastic network calculus (SNC). Due to the random nature of routing in MEC networks, probability parameters are introduced in the proposed analysis model to characterize this randomness into the derived expressions. Taking actual communication scenarios into consideration, the end-to-end performance of three network data-flows is analyzed, namely, voice over Internet protocol (VoIP), video, and file transfer protocol (FTP). These network data-flows adopt the preemptive priority scheduling scheme. Based on the arrival processes of these three data-flows, the effect of interference on their performances and the service capacity of each node in the MEC networks, closed-form expressions are derived for showing the relationship between delay, backlog upper bounds, and violation probability of the data-flows. Analytical and simulation results show that delay and backlog performances of the data-flows are influenced by the number of hops in the network and the random probability parameters of interference-flow (IF).     

Performance Analysis of Network Coding Based Two-Way Relay Wireless Networks Deploying IEEE 802.11

In this paper, we investigate the performance analysis of the IEEE 802.11 DCF protocol at the data link layer. We analyze the impact of network coding in saturated and non-saturated traffic conditions. The cross-layer analytical framework is presented in analyzing the performance of the encode-and-forward (EF) relaying wireless networks. This situation is employed at the physical layer under the conditions of non-saturated traffic and finite-length queue at the data link layer. First, a model of a two-hop EF relaying wireless channel is proposed as an equivalent extend multi-dimensional Markovian state transition model in queuing analysis. Then, the performance in terms of queuing delay, throughput and packet loss rate are derived. We provide closed-form expressions for the delay and throughput of two-hop unbalanced bidirectional traffic cases both with and without network coding. We consider the buffers on nodes are unsaturated. The analytical results are mainly derived by solving queuing systems for the buffer behavior at the relay node. To overcome the hidden node problem in multi hop wireless networks, we develop a useful mathematical model. Both models have been evaluated through simulations and simulation results show good agreement with the analytical results.     

Scaling properties of statistical end-to-end bounds in the network calculus

The stochastic network calculus is an evolving new methodology for backlog and delay analysis of networks that can account for statistical multiplexing gain. This paper advances the stochastic network calculus by deriving a network service curve, which expresses the service given to a flow by the network as a whole in terms of a probabilistic bound. The presented network service curve permits the calculation of statistical end-to-end delay and backlog bounds for broad classes of arrival and service distributions. The benefits of the derived service curve are illustrated for the exponentially bounded burstiness (EBB) traffic model. It is shown that end-to-end performance measures computed with a network service curve are bounded by /spl Oscr/(H log H), where H is the number of nodes traversed by a flow. Using currently available techniques, which compute end-to-end bounds by adding single node results, the corresponding performance measures are bounded by /spl Oscr/(H/sup 3/).     

A cross-layer framework for optimal delay-margin,network lifetime and utility tradeoff in wireless visual sensor networks

For wireless multimedia sensor networks a distributed cross-layer framework is proposed, which not only achieves an optimal tradeoff between network lifetime and its utility but also provides end-to-end delay-margin. The delay-margin, defined as the gap between maximum end-to-end delay threshold and the actual end-to-end delay incurred by the network, is exploited by the application layer to achieve any desired level of delay quality-of-service. For optimal performance tradeoff an appropriate objective function for delay-margin is required, which is obtained by employing sensitivity analysis. Sensitivity analysis is performed by incorporating delay-margin in the end-to-end delay constraints while penalizing its price in the objective function. For distributed realization of proposed cross-layer framework, the optimal tradeoff problem is decomposed into network lifetime, utility and delay-margin subproblems coupled through dual variables. The numerical results for performance evaluation show that compromising network utility does not guarantee both lifetime and delay-margin improvement, simultaneously, for the set of operating points. Performance evaluation results also reveal that the fairness among different delay-margins, corresponding to different source–destination node pairs, can be improved by relaxing the end-to-end delay threshold.     

A Cross-Layer Routing Scheme Using Adaptive Retransmission Strategy for Wireless Mesh Networks

In this paper, we develop a link quality-based adaptive adjustment mechanism of the MAC maximum retransmission count to reduce collision probability of wireless Mesh networks. Based on statistics acquired in the link layer and the retransmission strategy, a multi-metric cross-layer on-demand routing scheme is proposed for wireless Mesh networks. The proposed scheme uses information such as available link bandwidth, node residual load rate and transmission efficiency of a path adequately to cross-layer routing. The network layer can adaptively select an optimal path to deliver packets based on the acquired statistics of the MAC layer. Extensive simulation results demonstrate that the proposed scheme can reduce link failure probability, improve network throughput, and decrease the end-to-end delay effectively.     

泛在无线环境中多无线接入网协同的业务分配策略

This paper introduces an adaptive traffic allocation scheme with cooperation of multiple Radio Access Networks (RANs) in universal wireless environments. The different cooperation scenarios are studied, and based on the scenario of cooperation in both network layer and terminal layer, an open queuing system model, which is aiming to depict the characteristics of packet loss rate of wireless communication networks, is proposed to optimize the traffic allocation results. The analysis and numerical simulations indicate that the proposed scheme achieves internetworking load balance to minimize the whole transmission delay and expands the communication ability of single-mode terminals to support high data rate traffics.