计算机作战仿真中关于网络数据传输量问题的研究

计算机作战仿真已成为高技术条件下进行武器装备论证、武器性能评估、作战人员训练、战术战法研究甚至国家战略决策等不可或缺的一个环节。该文在介绍计算机作战仿真基本概念的基础上 ,重点讨论了分布式交互仿真中如何减少网络数据传输量的问题 ,提出了几种解决问题的技术 ,其中 ,重点介绍了DR算法的应用。

飞行仿真系统网络传输与同步技术

网络通信是分布环境下飞行仿真系统需要解决的关键技术,包括网络传输量和时钟同步等。网络传输量方面,采用DR模型降低了网络数据更新频率,减少了数据通信量,并采用数据封包、解包的方法降低了网络频繁调用带来的时间损耗;时钟同步方面,采用了硬件同步电路和软件高性能时钟相结合的时钟同步方案,确保了飞行仿真系统时间推进的严格同步。在此基础上,构建了基于适配器模式的、支持多协议的通信引擎网络中间件,将顶层应用和底层通信进行有效隔离,降低了应用层开发量,加快了系统集成效率,在多型飞机模拟器中得到了应用。

无线传感器网络中一种能量高效的skyline查询算法

针对分布式无线传感器网络环境下的skyline查询问题,提出了KSkySenor算法,有效地从传感器网络中获取更有意义的skyline结果;KSkySenor算法对感知数据进行预处理计算每个元组的支配能力,按照支配能力与各维度值之和对其进行排序,设计了一个基于聚簇的结构用于收集所有传感器读数,提出了一个剪枝方法用于渐进的从传感器网中获取skyline结果集;实验中分别改变传感器网络规模大小、数据维度、支配属性个数k,对KSkySensor算法进行测试,实验结果表明KSkySenor算法与先前的skyline查询处理算法相比具有很高效率,减少了无线传感器网络中的数据传输量,延长了网络生命周期。

云数据库中等宽直方图的分布式并行构造方法

直方图能够直观描述数据分布,在数据库查询优化中起着重要作用。然而在分布式云数据库场景中,现有直方图构建方法存在并行资源利用率低,网络传输量较高的问题。针对该问题,基于关系型云数据库提出一种等宽直方图的分布式并行构造方法。首先,根据集群中分布式存储的数据无关性,基于master-slave架构在直方图任务开始前由集群中请求发起节点对经RPC(remote procedure call)协议获取到的多个工作节点最值数据比较得到数据表在整个集群的全局最大值、最小值;然后,考虑到算法运行过程中数据传输量的优化,集群中工作节点对本地数据扫描、排序,划分至依据全局最值信息构建的直方图桶内,实现聚合子直方图的并行构建以提高集群计算资源利用率;最后,请求发起节点对并行构建的多个子直方图中边界值相等的桶频率值聚合得到全局直方图。算法利用分布式思想实现了关系型云数据库中直方图的构建,将计算任务划分成多个子任务并行执行,子直方图信息代替数据分片的传输大幅优化了网络带宽的负载。算法已应用于关系型云数据库内核以优化SQL语句执行路径的初始扫描开销、数据选择率等关键参数。人工合成数据与评分数据的实验结果证明,算法运行过程中的网络传输量与数据库表中元组个数无关,且具有良好的可拓展性。

A Learning-Based Channel Model for Synergetic Transmission Technology

It is extensively approved that Channel State Information(CSI) plays an important role for synergetic transmission and interference management. However, pilot overhead to obtain CSI with enough precision is a significant issue for wireless communication networks with massive antennas and ultra-dense cell. This paper proposes a learning- based channel model, which can estimate, refine, and manage CSI for a synergetic transmission system. It decomposes the channel impulse response into multiple paths, and uses a learning-based algorithm to estimate paths' parameters without notable degradation caused by sparse pilots. Both indoor measurement and outdoor measurement are conducted to verify the feasibility of the proposed channel model preliminarily.

通信局域网安全策略浅析

由于上网的数据遭到不同程度的破坏,被删除或被复制,数据的安全性和自身的利益受到严重威胁。因此,不论在局域网还是在广域网中,网络的安全措施应是能全方位地针对各种不同的威胁和脆弱性,这样才能确保网络信息的保密性、完整性和可用性。

A special solution to transmission capacity of ad hoc networks

This paper presents an approximate expression to transmission capacity of ad hoc networks by using stochastic geometry. For there is no general close-form expression to the transmission capacity of ad hoc networks, by using Taylor series, we obtain the exact series expression to transmission capacity first, then we take partial summation to yield an n-th order approximate expression. Further- more, compared with the exact expression under a special case, the accuracy of the n-th order ap- proximation has been studied. The numerical results show that the accuracy of the approximation is mainly determined by the order n, and a high accuracy can be obtained when the node density or the outage constraint is close to zero .

A Combined Admission and Priority Control Mechanism for Assuring Communication Quality in VANETs integrated with Wireless Mesh Networks

In this paper, we introduce a new combined priority and admission control mechanism applying in the VCN （Vehicular Communication Network） which is designed with an integration of the Vehicular Ad-hoc Networks （VANETs） based on standard IEEE 802.11 p and IEEE 802.11 s WMNs （Wireless Mesh Networks）. Simulation experiments are intensively investigated to evaluate the novel combined priority and admission control mechanism to assure quality of the I2V （Infrastructure to Vehicle） emergency services occurred during the time video flows are being delivered between content servers and cars. The simulation results show effectiveness of proposed priority and admission control schemes in term of the minimized end-to-end delay as well as the increase of throughput and PDR （Packet Delivery Ratio） of the emergency data flow.

Experimental Evaluation of TCP and ICMP in Network Measurement

Network measurement is an important approach to understand network behaviors, which has been widely studied. Both Transfer Control Protocol （TCP） and Interact Control Messages Protocol （ICMP） are applied in network measurement, while investigating the differences between the measured results of these two protocols is an important topic that has been less investigated. In this paper, to compare the differences between TCP and ICMP when they are used in measuring host connectivity, RTT, and packet loss rate, two groups of comparison programs have been designed, and after careful evaluation of the program parameters, a lot of comparison experiments are executed on the Internet. The experimental results show that, there are significant differences between the host connectivity measured using TCP or ICMP; in general, the accuracy of connectivity measured using TCP is 20%- 30% higher than that measured using ICMP. The case of RTT and packet loss rate is complicated, which are related to path loads and destination host loads. While commonly, the RTF and packet loss rate＂ measured using TCP or ICMP are very close. According to the experimental results, some advices are also given on protocol selection for conducting accurate connectivity, RTF and packet loss rate measurements.

Cross-Layer and One-Hop Neighbour-Assisted Video Sharing Solution in Mobile Ad Hoc Networks

Fast resources discovery and high Quality of Service(QoS) guarantee are the key determinants for efficient Mobile P2P(MP2P) video sharing.In this paper,we propose a CrossLayer and One-Hop Neighbour-Assisted Video Sharing(CNVS) solution in Mobile Ad Hoc Networks(MANETs).By making use of crosslayer approaches to bridge the overlay and the MAC layer and with the help of dissemination assisted by one-hop neighbours,CNVS intelligently builds the resource-centric self-organization node cluster group.In order to meet the QoS requirement,by making use of video resources access cost model,each peer can disconnect a less efficient connection with the original supplier and choose a peer that provides a low access cost as the new supplier.Simulation results also show how CNVS achieves lower average end-to-end delay,less average number of hops for video data delivery,lower routing overhead and packet loss rate,and higher network throughput than another state-of-the-art solution.

Interference Coordination for Secrecy Enhancement in Random Wireless Networks

The co-channel interference modeling is vital for evaluating the secrecy performance in random wireless networks,where the legitimate nodes and eavesdroppers are randomly distributed.In this paper,a new interference model is proposed from the userdominant perspective.The model can provide a better analytical assessment of secrecy performance with interference coordination for the presence of eavesdroppers.The typical legitimate is assumed to be located at the origin,and chooses the closest base station(BS) as its serving BS.The field of interferers is obtained by excluding the desired BSs(including the serving BS and its cooperative BS(s)).In contract with the exiting interference model,it is assumed that desired BSs and interferers belong to the same Poisson Point Process(PPP),and eavesdroppers are distributed according to another independent PPP.Based on this model,the average secrecy transmission capacity is derived in simply analytical forms with interference coordination.Analysis and simulation results show that the secrecy performance can be significantly enhanced by exploiting interference coordination.Furthermore,the average secrecy transmission capacity increases with increasing number of cooperative BSs.

Priority-Aware IP over Hierarchical WDM Ring Networks

WDM （wavelength division multiplexing） appears to be the solution of choice for providing a faster networking infrastructure that can meet the explosive growth of the Internet. It has the scalability problem with increasing the access node numbers in WDM ring architecture, so we further propose the alternatives of hierarchical WDM ring architecture. Since the traditional IP provides the best effort service only, the issue of supporting IP packets with QoS （quality of Service） transfer has become a crucial issue for multimedia transmission. We do so by addressing the priority-aware QoS model. Finally present performance analysis multiple classes of hierarchical WDM ring networks.

Traffic sensitive spectrum access scheme for cognitive radio networks

A traffic sensitive spectrum access scheme is proposed to satisfy the traffic load requirement of secondary users （SUs）. In the proposed design, SU only accesses available channels which can meet the traffic demand. To achieve this, the expected transmission time （E3W） of the SU is calcu- lated first based on the delivery ratio. Then, the channel idle time is estimated based on the activity of primary users （PUs）. Therefore, available channels with estimated idle time longer than ETr could be chosen. With high probability, the SU can finish transmission on these channels without disruption, thereby satisfying the traffic load demand of the SU. Finally, our method is extended to the multi-channel scenario where each SU can access multiple channels simultaneously. Performance analysis shows that our method satisfies the requirement of SUs while effectively improving the throughput.

Transferring Multi-Dimensional Quantum States and Preparing Quantum Networks in Cavity QED

In this paper we propose a scheme for transferring quantum states and preparing quantum networks. Compared with the previous schemes, this scheme is more efficient, since three or four-dimensional quantum states can be transferred with a single step and information interchange of three-dimensional quantum states can be realized, which is a significant improvement. It is based on the resonant interaction of a three-mode cavity field with an atom. As a consequence, the interaction time is shortened greatly. Furthermore, we give some discussions about the feasibility of the scheme.

Dynamic routing and wavelength assignment algorithm of optical satellite networks based on cross-layer design

In order to overcome the adverse effects of Doppler wavelength shift on data transmission in the optical satellite networks,a dynamic routing and wavelength assignment algorithm based on crosslayer design( CL-DRWA) is introduced which can improve robustness of the network. Above all,a cross-layer optimization model is designed,which considers transmission delay and wavelength-continuity constraint,as well as Doppler wavelength shift. Then CL-DRWA is applied to solve this model,resulting in finding an optimal light path satisfying the above constraints for every connection request. In CL-DRWA,Bellman-Ford method is used to find an optimal route and a distributed relative capacity loss method is implemented to get an optimal wavelength assignment result on the optimal route. Moreover,compared with the dynamic routing and wavelength assignment algorithm based on minimum delay strategy( MD-DRWA),CL-DRWA can make an improvement of 5. 3% on the communication success probability. Meanwhile,CL-DRWA can meet the requirement of transmission delay for real-time services.

Capacity Analysis for Dynamic Space Networks

To evaluate transmission rate of highly dynamic space networks,a new method for studying space network capacity is proposed in this paper. Using graph theory,network capacity is defined as the maximum amount of flows ground stations can receive per unit time. Combined with a hybrid constellation model,network capacity is calculated and further analyzed for practical cases. Simulation results show that network capacity will increase to different extents as link capacity,minimum ground elevation constraint and satellite onboard processing capability change. Considering the efficiency and reliability of communication networks,how to scientifically design satellite networks is also discussed.

Quantum Network Coding on Networks with Arbitrarily Distributed Hidden Channels

Although perfect quantum network coding has been proved to be achievable, it is stiU puzzling whether it is feasible whenever one or more of the channels are replaced by the hidden ones emerging from quantum entanglement. The question is answered in this paper. First, we propose a quantum network coding protocol over a butterfly network with two hidden channels. Second, we investigate a more generaJ situation, where d-level quantum letters are transmitted through the network containing arbitrarily distributed hidden channels, and prove that quantum network coding on such networks is still achievable.