Traditional Inverse Distance Weighted (IDW) method may fail to reconstruct Radio Environment Map (REM) accurately due to the distribution of sampling points usually not satisfy its uniformity requirement in complex environments. A method features Gaussian kernel function-IDW(GKF-IDW) driven by Gaussian Mixture Model (GMM) is proposed. Disordered spatial points can be clustered into multiple superimposed normal distribution sub-models through GMM. On the basis of IDW, Gaussian kernel function is added to fit the changes in interpolation weights within complex subspaces for REM reconstruction. Results verified that the proposed method has a significant advantage under different sampling numbers and can effectively reconstruct REM of the target area.

The Connected and Autonomous Vehicles (CAVs) is considered to be a promising technology to improve the traffic congestion. However, to realize its expected benefits, the real-time, accurate and forward-looking guidance message are required. Based on this, considering various practical constraints and the characteristics of the CAVs fully, multiple distributed edge computing servers are deployed at the network edge to provide the real-time storage and computation support in our paper. Furtherly, based on the fruitful deployment for edge computing servers, an efficient traffic flow online prediction model is constructed, which can adaptively modify according to the dynamic changes of the actual road traffic state, thus providing more accurate and forward-looking results. The simulation results based on MATLAB platform show the proposed deployment scheme for edge computing servers only needs more cost than the enumeration method. Moreover, compared with other baseline methods, the online prediction model proposed can improve 37.5%–76.9% in terms of prediction accuracy.

This paper investigates an unmanned aerial vehicle (UAV)-assisted mobile edge computing scenario, where multiple UAVs provide computational services for user devices (UDs) with different service priorities. Taking into account UDs' different service priorities as well as diverse computation-offloading demands, a satisfaction-model is proposed, which gives consideration to UDs' satisfaction degree toward the offloading services as well as the fairness of their offloading amount. We aim to maximise UDs' sum satisfaction by jointly optimising the offloading time allocation, computing time allocation, users' transmit power, as well as UAV trajectory. A non-convex optimisation problem is formulated and an effective solution framework is proposed, where the problem is decomposed into three sub-problems that are solved alternately and iteratively by applying successive convex approximation (SCA) technique. Numerical results show that the proposed scheme achieves higher satisfaction with lower standard deviation as compared to benchmark schemes.

计算机网络课程是各个院校理工科专业普遍开设的一门专业基础课，其教学内容也是理论教学与实践教学相结合。 常规的实验教学内容通常由抓包分析、商用路由器配置和网络编程等组成，这些内容存在着难度差异大，参与度受限，实验效果 不佳等问题。而 SDN（软件定义网络）作为近些年出现的网络新技术，具有使用灵活、控制方便、参与深入的特点。本文分析了 现有实验方法存在的问题和 SDN 的特点，初步分析了利用 SDN 搭建实验系统的可行性和有效性，并初步设计了 SDN 实验的基本 内容，以供读者借鉴。

无人集群是未来的发展趋势之一,它需要可靠稳定的通信网络实现内部互联互通,为复杂的集群行动提供有效的信息传输渠道.为组成该网络,满足集群特点和需求的网络架构是关键.首先,本文提出了一种适用于无人集群的全分布式软件定义网络架构,论证了其全分布、无中心、实时性强、架构动态和可扩充等诸多优点;其次,介绍了全分布式软件定义网络架构在无人集群系统组网以及实现与现有系统互联方面的优势;最后,以无人机集群里的延迟容忍网络作为一个应用实例,介绍了该架构在无人集群系统里的应用,并验证了架构的有效性.

分析了编队无人系统的数据传输需求,对无人系统的数据传输频段选择、MAC层协议设计、路由层协议设计、传输和应用层协议设计分别进行了讨论,并给出了方案建议.指出了数据传输方案设计中应注意的问题,强调在建设过程中,应杜绝建“烟囱”,以消息格式为抓手,进行顶层设计.

The past few years have witnessed a surge of wireless mesh networks (WMNs)-based applications and heterogeneous WMNs are taking advantage of multiple radio interfaces to improve network performance. Although many routing protocols have been proposed for heterogeneous WMNs, most of them mainly relied on hierarchical or cluster techniques, which result in high routing overhead and performance degradation due to low utilization of wireless links. This is because only gateway nodes are aware of all the network resources. In contrast, a unified routing protocol (e.g., optimal link state routing (OLSR)), which treats the nodes and links equally, can avoid the performance bottleneck incurred by gateway nodes. However, OLSR has to pay the price for unification, that is, OLSR introduces a great amount of routing overhead for broadcasting routing message on every interface. In this paper, we propose unified routing protocol (URP), which is based on passive bandwidth measurement for heterogeneous WMNs. Firstly, we use the available bandwidth as a metric of the unification and propose a low-cost passive available bandwidth estimation method to calculate expected transmission time that can capture the dynamics of wireless link more accurately. Secondly, based on the estimated available bandwidth, we propose a multipoint relays selection algorithm to achieve higher transmission ability and to help accelerate the routing message diffusion. Finally, instead of broadcasting routing message on all channels, nodes running URP transmit routing message on a set of selected high bandwidth channels. Results from extensive simulations show that URP helps improve the network throughput and to reduce the routing overhead compared with OLSR and hierarchical routing. Copyright (c) 2016 John Wiley & Sons, Ltd.

在导航卫星系统中,为了解决星间链路拓扑规划不合理而导致的星地信息传输时延大的问题,提出了一种新的星间链路规划方法.该方法优先考虑星地间的可视覆盖关系,保证卫星与地面站之间实时的信息传输.利用STK仿真软件构建了卫星网络拓扑,进而利用OPNET仿真软件完成了性能仿真验证.仿真结果表明,新的拓扑减小了星地数据传输的跳数和端到端时延,符合星地一体化的需求.

Over the years satellite networks has played an more and more important role, and there has been the trend to build Inter-Satellite Links (ISLs) in the satellite networks as the ISLs can provide high network flexibility and reliability. Integration is one of the important characteristics of the navigation system, and the network topology of the inter satellite has great influence on it, so it's necessary to improve the performance of navigation system through appropriate inter satellite link planning. Aiming at this problem, this paper firstly established the link planning principles, and then the visible coverage relationship is proposed for a satellite link allocation algorithm, which is the foundation of the network topology formation. The topology gives preference to the data transmission between satellite and ground, the simulation results show that this network topology has an advantage in hops and delay performance.

在综合分析光突发交换网络中组装算法对控制平面处理时延、数据平面资源利用效率和数据平面突发丢失率等多种性能指标的影响的基础上,提出了一种能够同时满足多种网络性能指标约束的边缘节点动态组装算法。该算法根据全网目标性能指标的约束,动态调整组装输出的突发长度和突发时间门限,从而实现同时满足全网链路资源利用率和控制平面突发丢失概率的双重性能约束。

该文分析和研究了光突发交换网络中控制平面处理时延、数据平面资源利用效率以及数据平面突发丢失率等性能需求对边缘节点组装算法的约束性.分析结果证实数据平面的性能对边缘节点的组装算法参数更加敏感.在网络性能多目标约束条件下,基于无波长转换器核心节点的光突发交换网络几乎不存在有效的组装门限.在核心节点采用主流光交换矩阵且期望突发碰撞概率在10-4以下时,核心节点输出端口的单纤波长转换器数量至少需要30个以满足网络性能需求的约束条件.

Unsegmented network coding (UNC) is a promising technology to overcome poor source information scheduling of segmented network coding (SNC) in large scale networks, where unresponsive feedback slacks the scheduling. However, three unsolved problems limit its applicability. First, UNC employs ACK on witness as the feedback. The frequently triggered witness-ACK will introduce considerable overhead and depress throughput. Second, a new constraint from practical decoding requirement on the slide window has recently been proved. The additional constraint will make UNC much different, which has not been studied. Third, although UNC may outperform SNC in large scale networks, it does not work well in small and moderate-sized networks, exhibiting poor universality. In this paper, we address these problems and propose the Adaptive unsegmented Network Coding (ANC). ANC applies technologies for improvements, which is derived through reinvestigating UNC (solve the second problem), to improve achievable throughput, and save a majority of control overhead (solve the first problem). In addition, ANC incorporates a novel hybrid source packets admission scheme and can well adapt to various network conditions (solve the third problem). Simulation results show that ANC outperforms both SNC and UNC in universal network conditions, and the throughput gain over both can be up to 22%.

The cross traffic intensity of the optical burst switching network is a key parameter for the edge node operations. This paper provides an estimate model for edge nodes to infer the cross traffic on the control plane of the bottleneck core node. A normal M/D/1 and a special M/G/1 queuing model are applied to core nodes without and with wavelength conversion device respectively. Service time of the special M/G/1 queuing model is dependent with the traffic load. Edge nodes can then estimate the cross traffic of the core node through a likelihood function as well as a moment estimator. The observing variable that input to the estimator is the sojourn time of the burst control packet which can be obtained by sampling the residual offset time.

文章首先分析了宽带通信网络课程的开设背景,然后根据课程自身的特点,对带宽通信网络双语教学的课堂教学设计和教学内容的设置、教学的手段和方法等方面进行了深入的实践与探索。由于课堂元素中引入了小班化的特征,通过学生的积极参与,使得双语教学取得了良好的教学效果。

The 802.11 standard supports multiple data transmitting rates. The "throughput fairness" characteristic of the standard DCF appears undesirable, because of the high rate nodes has same channel access probability with the low rate ones. COT-based fairness is proposed with the purpose of guaranteeing fairness and improving the aggregate throughput, but the COT fairness is achieved by adjusting stations' packet length and sending multiple back-to-back packets at one time, it not suitable for all applications. The main contribution of this paper is the proposal of a PCAP(Proportional Channel Access Probability) fairness index. The index evaluate the fairness by the CAP which is in proportion to the nodes' transmission rates. This paper also proposed a PCAP-based fairness algorithm. With our algorithm, the stations in WLAN can achieve PCAP-based fairness which is independent with nodes' packet length. Through exclusive simulations, we show that the PCAP-based fairness index and algorithm leads to significant improvements in aggregate throughput and all stations have proportional fairness under multi-rate condition.

In the past few decades, wireless networks based on different standards have been developed quickly, and the coexistence of multiple communication systems has turned into reality. Due to the need for mobile computing or pervasive computing, quick and accurate protocol identification and analysis technology is required. Rather than employing the traditional demodulation-based method that requires to implement all known protocol modules in one single device, in this paper, we fully analyze the features in both time domain and frequency domain of physical (PHY) layer signals that can be used to describe a protocol, and present a new method of identifying and analyzing protocols without demodulation, which uses PHY layer signals only. This method can be used in battlefield and other situations where demodulation is impractical. To validate the feasibility of our method, we implement a system using GNU Radio and Universal Software Radio Peripheral (USRP). The results show that the system can successfully identify three different signals (including Wi-Fi, Bluetooth and Zigbee signals) with frequency domain features, and detect the period of beacons in Wi-Fi networks with the help of time domain features.

A dynamic offset time assignment algorithm based on the measurement of cross traffic on control plane is proposed.This algorithm uses probe burst's drop ratio as observing variable to determine the core node,s background traffic and assigns offset time dynamically based on the measured result.Analysis and simulation show that this algorithm can get moderate offset time under target Insufficient Offset Time(IOT) drop ratio's restriction and obtain tradeoff between end to end delay and IOT ratio.

We propose a position-aware routing protocol for pre-handoff on OLSR (POS-OLSR) in Vehicular Ad-hoc Networks to minimize data loss when routing handoff. We develop a function mapping node's position to link metric and calculated the best route by minimize the path metric. To fitting with position-aware and pre-handoff method, we improved OLSR protocol with a novel MPR selected algorithm and protocol messages. Simulation results indicate that POS-OLSR performs better in Packet Delivery Ratio than traditional OLSR with different of nodes density, nodes moving speed and traffic load.

A cross traffic estimator is proposed based on the loss ratio of the probe packets. This method aims to estimate the future networks' available bandwidth such as optical switching networks. In these networks, node's processing time other than tight link becomes the bottleneck. Most popular estimate techniques neglect it. In the scheme, probe traffic intensity and its drop ratio are collected and fitted using the 1st order ordinary least squares (OLS) algorithm. OLS adopts probe traffic intensity as dependent variable and its drop ratio as independent variable. Then the intercept difference between fitted line and empirical line is just the cross traffic. Simulation shows that our scheme can obtain the bottleneck node cross traffic appropriately and outperforms the minimal backlogging algorithm which is also based M/G/1 model.