基于可变距离的车联网D2D通信连接选择

车联网是移动互联网的延伸,其中基站协作的D2D通信适用于车间交通消息的短距离无线传播.针对车辆快速移动导致的通信链路动态性,提出了一种基于可变距离的D2D连接选择方法.通过选择行车道及车间距离参数,估计D2D连接对的信道质量,推导了D2D连接选择的优先指数,并基于该优先指数建立D2D通信链路进行交通消息传播.仿真结果显示,所提方法在D2D连接的生存时间、传输效率方面得到提高,同时降低了D2D通信的中断概率,提升了车辆间通信可靠性.     

Routing in wireless/mobile ad‐hoc networks via dynamic group construction

An ad-hoc network is temporarily formed by a group of mobile hosts communicating over wireless channels without any fixed network interaction and centralized administration. When a mobile host communicates with other mobile hosts in an ad-hoc network, the routes are established via the intermediate mobile hosts as forwarding nodes. Under such a network environment an adaptive approach for routing management will be proposed in this paper. In this approach, at first the network infrastructure is constructed by several communication groups, which are called routing groups. A routing group communicates with other routing groups via the boundary mobile hosts as forwarding nodes. In a routing group the mobile hosts are divided, by means of the dominating values, into two groups – one positive cluster and several non-positive clusters. The nodes in the positive cluster maintain the topology information of the routing group. Under such a construction environment, intra-group routing performs unicasting and gets multiple paths, while inter-group routing performs on group level by propagating the route requests to the boundary clusters, which are called bridge clusters. This routing scheme massively reduces the message complexity that is especially important for system performance under such a resource constraint environment. As far as the dynamic topology characteristics of ad-hoc networks are concerned, this approach also provides a more efficient infrastructure update. Finally, simulation results show that the routing via dynamic group construction outperforms the previous works in message complexity and infrastructure update efficiency. This revised version was published online in June 2006 with corrections to the Cover Date.     

Analysis for bio-inspired thrown-box assisted message dissemination in delay tolerant networks

Inspired by biological communication, the strategy of deploying communication and storage equipment called thrown box is proposed to increase message delivery probability and to reduce transmission latency in delay tolerant networks. In this paper, we study the thrown-box assisted message dissemination models by analyzing a few cases on the message delivery rate and related latency distribution. We divide such communications into two processes. We first model the message delivering process among thrown boxes and derive time related message distribution on the boxes. Then we investigate the message collection process to obtain the expected number of informed collectors as a function of time. In addition, we analyze the latency distribution for message collection. Our analysis is derived based on a discrete Markov Chain model. The numerical examples are provided to validate our model and to examine the features of message dissemination under different network scenarios. The factors such as message relay and lifetime are considered. The results show that the tradeoff exists between the number of the boxes and the message lifetime, etc. In summary, our results will help storage management and delay management in DTNs and provide guidelines for applications of search and surveillance.     

On the reliability and performance of real-time one-hop broadcast MANETs

Recently, broadcast communications in mobile ad hoc networks (MANETs) have been deployed in many mission-critical applications. So far, most investigations of such broadcast networks focus on multi-hop connectivity taking all one-hop links for granted. In this paper, the reliability and performance of real-time one-hop broadcast services in IEEE 802.11 based MANETs are investigated analytically and by simulation. Having specified possible applications and the features of IEEE 802.11 broadcast communication in dynamically self-organized networks under harsh communication environment, analyses are conducted to derive closed form expressions of the reliability and performance indices for both one-dimensional (1-D) and two-dimensional (2-D) broadcast MANETs: packet reception rate (PRR) and packet transmission delay. The proposed analytical models account for the impact of broadcast hidden terminal problem, message arrival interval, backoff counter process, space distributions of nodes, and fading transmission channel on the reliability and performance of the broadcast MANETs. As an example, the proposed models are applied to the evaluation of safety-related inter-vehicle communication on a highway. From the obtained numerical results under various offered traffic and network parameters, new observations and effective enhancement suggestions are given.     

A Dual Ring Connectivity Model for VANET Under Heterogeneous Traffic Flow

Vehicular ad-hoc network (VANET) is characterized as a highly dynamic wireless network due to the dynamic connectivity of the network nodes. To achieve better connectivity under such dynamic conditions, an optimal transmission strategy is required to direct the information flow between the nodes. Earlier studies on VANET’s overlook the characteristics of heterogeneity in vehicle types, traffic structure, flow for density estimation, and connectivity observation. In this paper, we have proposed a heterogeneous traffic flow based dual ring connectivity model to enhance both the message disseminations and network connectivity. In our proposed model the availability of different types of vehicles on the road, such as, cars, buses, etc., are introduced in an attempt to propose a new communication structure for moving vehicles in VANETl under cooperative transmission in heterogeneous traffic flow. The model is based on the dual-ring structure that forms the primary and secondary rings of vehicular communication. During message disseminations, Slow speed vehicles (buses) on the secondary ring provide a backup path of communication for high speed vehicles (cars) moving on the primary ring. The Slow speed vehicles act as the intermediate nodes in the aforementioned connectivity model that helps improve the network coverage and end-to-end data delivery. For the evaluation and the implementation of dual-ring model a clustering routing scheme warning energy aware cluster-head is adopted that also caters for the energy optimization. The implemented dual-ring message delivery scheme under the cluster-head based routing technique does show improved network coverage and connectivity dynamics even under the multi-hop communication system.     

An efficient communication relay placement algorithm for content‐centric wireless mesh networks

In this paper, we investigate a communication relay placement problem to optimize the network throughput in a content‐centric wireless mesh networks (WMN), in which the WMN is enhanced by including a small set of communication relays and a subset of wireless mesh routers serving as storage nodes. Specifically, we first define the communication relay placement problem in content‐centric WMNs. We then model the problem as a mathematical programming and propose a linear programming approach for calculating the achievable network throughput when the positions of communication relays are fixed. Next, to optimally placing the communication relays, we formulate an integer linear programming problem and we develop an efficient near‐optimal approximation algorithm based on linear programming relaxation. Finally, extensive simulation experiments have been conducted, and the results demonstrate the effectiveness of the proposed algorithms. Copyright © 2013 John Wiley & Sons, Ltd.     

A novel caching scheme for improving Internet-based mobile ad hoc networks performance

Internet-based mobile ad hoc network (Imanet) is an emerging technique that combines a wired network (e.g. Internet) and a mobile ad hoc network (Manet) for developing a ubiquitous communication infrastructure. To fulfill users’ demand to access various kinds of information, however, an Imanet has several limitations such as limited accessibility to the wired Internet, insufficient wireless bandwidth, and longer message latency. In this paper, we address the issues involved in information search and access in Imanets. An aggregate caching mechanism and a broadcast-based Simple Search (SS) algorithm are proposed for improving the information accessibility and reducing average communication latency in Imanets. As a part of the aggregate cache, a cache admission control policy and a cache replacement policy, called Time and Distance Sensitive (TDS) replacement, are developed to reduce the cache miss ratio and improve the information accessibility. We evaluate the impact of caching, cache management, and the number of access points that are connected to the Internet, through extensive simulation. The simulation results indicate that the proposed aggregate caching mechanism can significantly improve an Imanet performance in terms of throughput and average number of hops to access data items.     

A short ID‐based proxy signature scheme

The notion of identity‐based proxy signature with message recovery feature has been proposed to shorten identity‐based proxy signatures and improve their communication overhead because signed messages are not transmitted with these kinds of signatures. There are a few schemes for this notion: the schemes of Singh and Verma and Yoon et al. Unfortunately, Tian et al., by presenting two forgery attacks, show that Singh and Verma scheme is not secure, and also, the scheme of Yoon et al. does not support provable security. The contributions of this paper are twofold. First, we review the scheme by Yoon et al. and discuss why it does not have message recovery property, and consequently, it is not short. Second, we propose a short identity‐based proxy signature scheme with the help of message recovery property and show that it is secure under computational Diffie–Hellman assumption in the random oracle model. Furthermore, our scheme is more efficient than (as efficient as) previous identity‐based proxy signatures. Copyright © 2014 John Wiley & Sons, Ltd.     

Self-healing group key distribution with time-limited node revocation for wireless sensor networks

A novel key distribution scheme with time-limited node revocation is proposed for secure group communications in wireless sensor networks. The proposed scheme offers two important security properties: the seal-healing re-keying message distribution which features periodic one-way re-keying with implicitly authentication, efficient tolerance for the lost re-keying messages, and seamless Traffic Encryption Key (TEK) switch without disrupting ongoing data transmissions; and the time-limited dynamic node attachment and detachment, so that both forward and backward secrecy is assured by dual directional hash chains. It is shown that the communication and computation overhead of the proposed protocol is light, and the protocol is robust under poor communication channel quality and frequent group node topology change.     

Integrated service discovery architecture for heterogeneous networks

The discovery and management of desired network services present significant challenges for mobile networks. Based on the Service Location Protocol, this paper proposes an integrated service discovery architecture for vehicular ad hoc networks. The proposed approach divides the network into several logical zones. The zone structure is formed virtually based on position information. Each logical zone may have a zone directory agent to manage registered services from service providers. The proposed architecture considers both vehicle‐to‐infrastructure and vehicle‐to‐vehicle communication modes and introduces roadside directory agents and vehicle directory agents to reduce deployment costs. We also introduce a substitute query technique, cache mechanism, and backup mechanism to improve the request hit ratio and reduce the message overhead of the substitute query. Finally, we implement the proposed mechanisms in Network Simulator version 2, with simulation results showing that the proposed architecture can provide a high average data hit ratio and low message overhead. Copyright © 2016 John Wiley & Sons, Ltd.     

Energy efficient collaborative communications in AWGN and Rayleigh fading channel in wireless sensor networks

Collaborative communication produces high power gain and significantly reduces bit error rate (BER) if both frequency and phase synchronization are achieved. In this paper, a novel collaborative communication system with imperfect phase and frequency synchronization that includes the influence of noise and fading is proposed, modeled, theoretically analyzed, and simulated. Mathematical expressions are derived for the received power as a function of number of collaborative nodes and BER as a function of signal to noise ratio (E_b ∕ N₀). To analyze the energy efficiency of our proposed collaborative communication system, energy consumption of the system is modeled, simulated, and analyzed by considering the parameters of the off‐the‐shelf products. Analytical and simulation results showed that the proposed system produces significant power gain and reduction in BER in the presence of phase errors, frequency errors, additive white Gaussian noise, and Rayleigh fading. A detailed theoretical analysis and Monte Carlo simulation revealed that the proposed collaborative communication system is an energy efficient communication system that can be implemented in sensor networks, as approximately N (number of collaborative nodes) times less total transmitted power is required than for the single input single output communication for a specifies transmission range. Copyright © 2012 John Wiley & Sons, Ltd.     

基于HARQ机制的数据链通信性能分析

利用JTIDS数据链现有的编码体制提出了一种基于HARQ机制的数据链通信模式,以提高报文传输的可靠性.首先对JTIDS系统的时隙结构进行改进,建立了HARQ机制的反馈信道,以保证该通信模式的实现;然后分析了JTIDS数据链系统在莱斯信道环境下的符号误码率,并在此基础上采用Markov模型对基于HARQ机制的数据链通信模式进行性能分析,评估了在该机制下通信的吞叶量、报文到达率、报文服务率和报文传输服务时延;最后,利用GSPN网对基于HARQ机制的数据链通信模式进行仿真分析,仿真结果表明采用HARQ机制的数据链通信系统能够很好地改善在恶劣信道环境下的报文传输能力,提高报文传输的可靠性.     

基于细菌趋药性算法的盲图像分离方法

提出了一种新的基于细菌趋药性(BC)算法的盲图像分离方法,利用图像信号的规范四阶累积量作为目标函数,使用BC算法对目标函数进行优化以实现图像的盲分离。每分离出一幅图像后,从混合图像中消除该幅图像成分后再进行下一次分离,从而最终实现所有源图像的逐次分离。仿真结果表明,本文算法能够有效实现对多幅混合自然图像的盲分离,且具有较好的分离效果。     

基于变量节点串行策略的SCMA低复杂度译码研究

稀疏码多址接入(SCMA)技术作为5G无线通信网络的一个竞争性的非正交多址方案,具有广阔的应用前景.但目前基于SCMA的上行链路均采用泛洪方案的消息传递算法(MPA)进行译码,无论是检测的复杂度还是收敛速度都不甚理想.提出一种改变信息更新策略的串行消息传递算法——S-MPA (serial MPA),按照变量节点的次序进行消息处理和传递,每一个变量节点同时进行校验消息的接收和变量消息的发送.理论和仿真结果表明,该算法不仅能保持良好的性能,而且也有较低的解码复杂度.     

An extended core‐based framework for delay‐constrained group communication

Multipoint communications is the simultaneous transmission of data streams from a number of sources to a set of receivers in a group according to predetermined metrics. The core‐based approach in multipoint communication enhances potential solutions in terms of quality‐of‐service (QoS)‐efficiency and feasibility of the results in inter and intra‐domain routing. In this paper, we first analyse the solution space for constrained multipoint communication problems under the core‐based approach. We show that the range of solutions examined by the models proposed to date is restricted to a subset of the entire solution space, which restricts the potential efficiency of the results. We propose SPAN, a core‐based framework processing on our identified extended solution space for constrained multi‐source group applications. SPAN consists of core selection and tree construction as two modular components complimenting one another to achieve more efficient solutions in distributed processing. SPAN is also asymmetric, hence potentially operates in domains in which link weights are not necessarily equal in both directions. We analyse the computational and message complexity of our framework and show its feasibility for distributed deployment. Our performance results show that SPAN consistently outperforms its counterparts in the literature in terms of cost and QoS‐efficiency. Copyright © 2007 John Wiley & Sons, Ltd.     

基于混沌参数调制的数字通信方式

提出一种基于混沌参数调制的数字通信方式。即将一个由非线性映射所产生的混沌序列作为载波,将待发送的有用信号（数字信号）作为调制信号,对非线性映射的某一参数在其混沌区域内进行调制。在接收端,利用混沌序列的发生规则从接收信号中提取混沌载波,并经过简单的信号处理运算恢复出原来的有用信号。分析和计算机模拟表明,本文所提出的这种混沌通信系统具有一定的保密性且实现方便、性能可靠     

Cooperative communication for safety message dissemination in unsaturated networks with varying contention windows

Safety message dissemination is crucial in vehicular ad hoc networks (VANETs) for road safety applications. Vehicles regularly transmit safety messages to surrounding vehicles to prevent road accidents. However, changing vehicle mobility and density can cause unstable network conditions in VANETs, making it inappropriate to use a fixed contention window (CW) for different network densities. It has been proposed a 1-D Markov model under unsaturation conditions to analyze the performance of the system with varying CWs under changing vehicle densities. Additionally, it introduces the use of cooperative communication (CoC) to relay failed safety messages. In CoC, two control packets, namely, negative acknowledge (NACK) and enable to cooperate (ETC), are utilized. The proposed analytical model named cooperative communication for safety message dissemination (CoC-SMD) is used to calculate throughput and average packet delay for varying CW and different packet size. The simulation confirms the validity of the analytical results and show significant improvement in the metrics through the use of varying CW sizes and CoC compared with existing techniques.     

基于正态分布宽带信号的无源互调特征行为分析

在现代无线通信中,无源互调是影响通信信号传输质量的重要因素。双音互调测试能够有效衡量无源器件的非线性特性,却无法准确预测出器件在宽带信号激励下的非线性失真。因此本文提出了一种基于正态分布的宽带信号激励下的射频连接器无源互调特性分析方法。通过双音互调测试,建立射频连接器无源非线性传输数学模型,并将基于正态分布的等效宽带信号作为非线性传输模型的激励源进行模拟仿真。结果表明,宽带无源互调功率分布与宽带信号功率分布相同,n阶宽带无源互调带宽为原宽带信号带宽的n倍,宽带信号的无源互调产物相较于双音测试信号有所增强,且信号的信噪比下降,说明宽带信号在传输过程中受到的干扰更加严重。电路仿真和数值计算呈现出良好的一致性,证明了本分析方法的有效性。     

Effects of message encoding and decoding on synchronized chaotic optical communications

Chaotic optical communication at 2.5 Gb/s is experimentally investigated using three major encoding and decoding schemes, namely chaos shift keying (CSK), chaos masking (CMS), and additive chaos modulation (ACM). The effects of message encoding and decoding on the chaotic dynamics, the chaos synchronization, and the chaotic communication performance are compared among the three schemes. In the schemes of CSK and ACM, it is found that a small amount of message injected into the chaotic dynamics can increase the complexity of the chaotic state dramatically. In the CMS scheme, the chaotic dynamics are found not to be influenced by the encoded message. The synchronization quality deteriorates dramatically with an increase in the message strength in CSK and CMS. The ACM scheme is found to have the best synchronization quality among the three schemes when there is an encoded message. Message recovery is demonstrated for each of the three schemes. The ACM scheme is found to have the best communication performance.