An intelligent infotainment dissemination scheme for heterogeneous vehicular networks

In a vehicular network, applications are expected to be aware of network conditions and be adaptable to the varying environment in order to achieve the acceptable and predictable performance. Moreover, the establishment of vehicle infotainment system in a heterogeneous vehicular network needs to pay special attention to the distinctive network characteristic in wired/wireless networks, such as dynamic topology and less available bandwidth, and the exploitation of the underutilized peers’ resources to support large-scale services. This work thus proposes a service-oriented information dissemination scheme for vehicle infotainment system to ensure the possibility of heterogeneous vehicular communication and a framework for delivering real-time services over an IP-based network is provided to assure interoperability, roaming, and end-to-end session management. The main focus of this work is to implement an adaptive vehicle infotainment system, in which cache relay nodes ((Xiao, Zhuang, & Liu, 2005)) can be intelligently determined. Fuzzy logic inference system is employed to determine appropriate cache relay nodes to cache infotainment data streams and distribute them to different peers through service-oriented architecture. The experimental results demonstrate that effectiveness and practicability of the proposed work.     

A Comparative analysis of Green’s functions of 1D matching equations for motion synthesis

When filtering an input image, the Green’s functions of matching equations are capable of inducing a broad class of motions, a property that has led to their use in several computer graphics and computer vision applications. In all such applications, the Green’s functions of second-order differential equations have been considered, even though no justification has been given for their preference over simpler, first-order equations. Here we present a study of first-order one-dimensional matching equations, both in the uniform and in the affine motion models. Comparing their Green’s functions with those of the corresponding second-order cases, we find evidence for the latter’s superiority in motion synthesis. We also propose and discuss a general discretization scheme for Green’s functions of one-dimensional matching equations, showing that the affine motion model is particularly sensitive to the sampling frequency. In this case, we advocate the use of area sampling, for allowing realistic motion simulations.     

A router architecture for flexible routing and switching inmultihop point-to-point networks

Modern parallel and distributed applications have a wide range of communication characteristics and performance requirements. These diverse characteristics affect the performance and suitability of particular routing and switching policies in multihop point-to-point networks. In this paper, we identify a core set of architectural features necessary for flexible selection and implementation of multiple routing and switching schemes. Using this, we present a flexible router whose routing and switching policies can be tailored to the application, allowing the network to meet these diverse needs. By dedicating a small programmable processor to each incoming link, we can implement wormhole, virtual cut-through, and packet switching, as well as hybrid switching schemes, each under a variety of unicast and multicast routing algorithms. In addition, a flexible router can support several applications or traffic types simultaneously, enabling better support of applications with multiple traffic classes. We have designed, implemented, and fabricated the Programmable Routing Controller (PRG). Cycle-level simulations of mesh-connected PRCs also demonstrate that flexible routing and switching can significantly enhance application performance     

Exploiting the potential of DTN for energy-efficient internetworking

Since its original conception as a space-oriented communications architecture, Delay Tolerant Networking (DTN) has been generalized to address issues in terrestrial networks as well. In this work we employ DTN to form an internetworking overlay that exploits the surplus capacity of last hop wireless channels in order to prolong battery life for mobile networking devices. We propose a novel rendezvous mechanism and show experimentally that the DTN overlay can shape traffic, allowing the wireless interface of the mobile device to switch to the sleep state during idle intervals without degrading performance. The simulation experiments are based on a comprehensive DTN agent that incorporates the rendezvous mechanism and facilitates quantifying energy conservation. The DTN agent, implemented in ns-2, enables the study of additional Bundle Protocol design issues, such as route selection, bundle sizing, retransmission strategies, and highlights the need for cross-layer interaction between DTN and the underlying transport protocol.     

An efficient three-party authenticated key exchange protocol using elliptic curve cryptography for mobile-commerce environments

For secure communications in public network environments, various three-party authenticated key exchange (3PAKE) protocols are proposed to provide the transaction confidentiality and efficiency. In 2008, Chen et al. proposed a round-efficient 3PAKE protocol to provide the computation and communication efficiency for user authentication and session key exchange. However, we discover that the computation costs and communication loads of their protocol are still high so that it cannot be applied to mobile communications. Therefore, we propose an efficient three-party authenticated key exchange protocol based upon elliptic curve cryptography for mobile-commerce environments. Because the elliptic curve cryptography is used, the proposed 3PAKE protocol has low computation costs and light communication loads. Compared with Chen et al.’s protocol, the proposed protocol is more suitable and practical for mobile-commerce environments.     

Enabling opportunistic storage for mobile DTNs

Delay-tolerant Networking (DTN) can enable ad-hoc communication within (sparse) mobile user communities and multi-hop Internet access where IP-based end-to-end communication would fail. DTN message forwarding in ad-hoc networks may lead to message replication and messages remaining stored on several nodes for some time. We leverage these characteristics and provide application support in intermediate nodes: we enable them to understand the resources contained in forwarded and locally stored DTN messages to perform application-specific processing. Based upon this, we create an opportunistic distributed storage for cooperative content caching and retrieval using the nodes’ buffers.     

Towards secure and communication-efficient broadcast encryption systems

Many emerging network applications are based upon a group communication model where security is a critical design issue. We address the broadcast encryption problem of distributing to a group of network entities a confidential cryptographic key, which needs to be updated from session to session. The design goals of such a system essentially include not only security but also communication efficiency concerning the distribution of the session key. We show that there is a disconnect between the essence of broadcast encryption and a scheme proposed very recently. The observation also motivates us to seek for secure and efficient broadcast encryption solutions. Three distinctive constructions, based on the bilinear map, the one-way hash function, and the RSA cryptosystem, respectively, are then presented to demonstrate reasonable tweaks and various tradeoffs when designing practical group-oriented communication systems. These constructions exhibit not only promising security but also impressive communication efficiency, and we also discuss the diverse networking scenarios to which they are applicable.     

Shared State for Distributed Interactive Data Mining Applications

Distributed data mining applications involving user interaction are now feasible due to advances in processor speed and network bandwidth. These applications are traditionally implemented using ad-hoc communication protocols, which are often either cumbersome or inefficient. This paper presents and evaluates a system for sharing state among such interactive distributed data mining applications, developed with the goal of providing both ease of programming and efficiency. Our system, called InterAct, supports data sharing efficiently by allowing caching, by communicating only the modified data, and by allowing relaxed coherence requirement specification for reduced communication overhead, as well as placement of data for improved locality, on a per client and per data structure basis. Additionally, our system supports the ability to supply clients with consistent copies of shared data even while the data is being modified.We evaluate the performance of the system on a set of data mining applications that perform queries on data structures that summarize information from the databases of interest. We demonstrate that providing a runtime system such as InterAct results in a 10–30 fold improvement in execution time due to shared data caching, the applications' ability to tolerate stale data (client-controlled coherence), and the ability to off-load some of the computation from the server to the client. Performance is improved without requiring complex communication protocols to be built into the application, since the runtime system uses knowledge about application behavior (encoded by specifying coherence requirements) in order to automatically optimize the resources utilized for communication. We also demonstrate that for our benchmark tests, the quality of the results generated is not significantly deteriorated due to the use of more relaxed coherence protocols.     

延迟／中断容忍网络发展研究

延迟／中断容忍网络（DTN）具有长延时、某一时刻不存在端到端链路或者链路频繁中断等特点,作为一种新型体系结构,近年来受到广泛关注与研究。介绍了DTN网络的研究现状,分析了其体系结构特点,详细描述了目前DTN关键技术包括网络协议、路由与安全机制方面的研究进展及面临的挑战,最后介绍了DTN在深空探测、军事通信等领域的应用,指出了DTN在未来通信网络发展中的作用。     

基于最近社交圈的社交时延容忍网络路由策略

无稳定拓扑使时延容忍网络(delay tolerant networks,DTN)路由协议主要通过增加冗余数据包副本提高路由性能.社交网络是DTN的一种典型应用场景,但由于其网络规模相对较大,当网络负载高时,通常的DTN路由不能有效控制数据包副本的数量,从而产生大量丢包导致性能下降.借鉴MANET网络中利用分簇结构控制网络冗余路由数据包的思想,通过分析社交网络中节点的移动模型,定义了在社交关系的约束下,聚合移动规律相近的节点构成最近社交圈的节点簇组成策略.提出了一种基于该分簇结构的分为簇外喷射、簇间转发和簇内传染3个阶段的社交时延网络路由协议.实验证明,这种基于最近社交圈分簇结构的路由能有效地控制冗余数据包副本的产生,并在高网络负载的情况下仍然能够达到较好的性能.     

Endeavouring to be in the good books. Awarding DTN network use for acknowledging the reception of bundles

This paper describes an incentive scheme for promoting the cooperation, and, therefore, avoiding selfish behaviours, in Delay Tolerant Networks (DTN) by rewarding participant nodes with cryptographic keys that will be required for sending bundles. DTN are normally sparse, and there are few opportunistic contacts, so forwarding of other’s bundles can be left out. Moreover, it is difficult to determine the responsible nodes in case of bundle loss. The mechanism proposed in this paper contributes to both problems at the same time. On one hand, cryptographic receipts are generated using time-limited Identity Based Cryptography (IBC) keys to keep track of bundle transmissions. On the other hand, these receipts are used to reward altruistic behaviour by providing newer IBC keys. Finally, these nodes need these IBC keys to send their own bundles. When all nodes behave in a cooperative way, this incentive scheme works as a virtuous circle and achieves a Nash equilibrium, improving very much the network performance in terms of latency. The scheme is not difficult to implement, and it can use an already existing IBC infrastructure used for other purposes in a DTN.     

Scheduling support for multicasting sessions in broadband communication networks

Multimedia applications require support from the underlying broadband network at the end-to-end communication level. Multicasting is an important paradigm of end-to-end communication. The root node of a multicasting session is responsible for controlling the session including monitoring, maintenance, and the implementation of the multicasting protocol. The job that controls the multicasting session executes as a group of tasks at the root node of a multicasting tree. The scheduling scheme at the root node should give support to a multicasting session by improving the completion time of the jobs controlling the multicasting session, hence increasing throughput and the probability of admitting new multicast sessions into the system. In this paper, we model the tasks that carry out the multicasting session monitoring and maintenance as a fork-join job executing on a multiprocessor system. We assume that an executing task blocks for device I/O as a part of the activities associated with sending and receiving data packets. We develop two analytic models for scheduling a session control job on a multiprocessor system. The first model allows incoming job tasks to multiplex processors with existing tasks of another multicasting session, while the other model schedules a task of the incoming job to an idle processor. We assume that the overhead of rescheduling a task to another processor is large. We compare the performance of both models and show the range of conditions under which a model outperforms the other. We point out how the results can be used in the design of an adaptive scheduler that uses both models to improve throughput and consequently the probability of admitting new multicast sessions.     

Non-linear protocols for optimal distributed consensus in networks of dynamic agents

We consider stationary consensus protocols for networks of dynamic agents with fixed topologies. At each time instant, each agent knows only its and its neighbors’ state, but must reach consensus on a group decision value that is function of all the agents’ initial state. We show that the agents can reach consensus if the value of such a function is time-invariant when computed over the agents’ state trajectories. We use this basic result to introduce a non-linear protocol design rule allowing consensus on a quite general set of values. Such a set includes, e.g., any generalized mean of order p of the agents’ initial states. As a second contribution we show that our protocol design is the solution of individual optimizations performed by the agents. This notion suggests a game theoretic interpretation of consensus problems as mechanism design problems. Under this perspective a supervisor entails the agents to reach a consensus by imposing individual objectives. We prove that such objectives can be chosen so that rational agents have a unique optimal protocol, and asymptotically reach consensus on a desired group decision value. We use a Lyapunov approach to prove that the asymptotical consensus can be reached when the communication links between nearby agents define a time-invariant undirected network. Finally we perform a simulation study concerning the vertical alignment maneuver of a team of unmanned air vehicles.     

Empirical Optimization for a Sparse Linear Solver: A Case Study

This paper describes initial experiences with semi-automated performance tuning of a sparse linear solver in LS-DYNA, a large, widely used engineering application. Through a collection of tools supporting empirical optimization, we alleviate the burden of performance tuning for mapping today’s sophisticated engineering software to increasingly complex hardware platforms. We describe a tool that automatically isolates code segments to create benchmark subsets for the purposes of performance tuning. We present a collection of automatically generated empirical results that demonstrate the sensitivity of the application’s performance to optimization parameters. Through this case study, we demonstrate the importance of developing automatic performance tuning support for performance-sensitive applications.     

Implement web learning environment based on data mining

The need for providing learners with web-based learning content that match their accessibility needs and preferences, as well as providing ways to match learning content to user’s devices has been identified as an important issue in accessible educational environment. For a web-based open and dynamic learning environment, personalized support for learners becomes more important. In order to achieve optimal efficiency in a learning process, individual learner’s cognitive learning style should be taken into account. Due to different types of learners using these systems, it is necessary to provide them with an individualized learning support system. However, the design and development of web-based learning environments for people with special abilities has been addressed so far by the development of hypermedia and multimedia based on educational content. In this paper a framework of individual web-based learning system is presented by focusing on learner’s cognitive learning process, learning pattern and activities, as well as the technology support needed. Based on the learner-centered mode and cognitive learning theory, we demonstrate an online course design and development that supports the students with the learning flexibility and the adaptability. The proposed framework utilizes data mining algorithm for representing and extracting a dynamic learning process and learning pattern to support students’ deep learning, efficient tutoring and collaboration in web-based learning environment. And experiments do prove that it is feasible to use the method to develop an individual web-based learning system, which is valuable for further study in more depth.     

On the implications of routing metric staleness in delay tolerant networks

Delay Tolerant Network (DTN) routing addresses challenges of providing end-to-end service where end-to-end data forwarding paths may not exist. The performance of current DTN routing protocols is often limited by routing metric “staleness”, i.e., routing information that becomes out-of-date or inaccurate because of long propagation delays. Our previous work, ParaNets, proposed a new opportunistic network architecture in which the data channel is augmented by a thin end-to-end control channel. The control channel is adequate for the exchange of control traffic, but not data. In this paper we present Cloud Routing, a routing solution for the ParaNets architecture. We motivate the need for such a solution, not only because of stale routing metrics, but also because of congestion that can occur in DTNs. Unable to use up-to-date routing metrics to limit congestion, existing DTN routing solutions suffer from low goodput and long data delivery delays. We show how Cloud Routing avoids congestion by smart use of forwarding opportunities based on up-to-date routing metrics. We evaluate our solution using extensive OPNET simulations. Cloud Routing extends network performance past what is currently possible and motivates a new class of globally cognizant DTN routing solutions.     

Verification of probabilistic systems with faulty communication

Many protocols are designed to operate correctly even in the case where the underlying communication medium is faulty. To capture the behavior of such protocols, Lossy Channel Systems (LCS’s) have been proposed. In an LCS the communication channels are modeled as unbounded FIFO buffers which are unreliable in the sense that they can nondeterministically lose messages. Recently, several attempts have been made to study Probabilistic Lossy Channel Systems (PLCS’s) in which the probability of losing messages is taken into account. In this article, we consider a variant of PLCS’s which is more realistic than those studied previously. More precisely, we assume that during each step in the execution of the system, each message may be lost with a certain predefined probability. We show that for such systems the following model-checking problem is decidable: to verify whether a linear-time property definable by a finite-state ω-automaton holds with probability one. We also consider other types of faulty behavior, such as corruption and duplication of messages, and insertion of new messages, and show that the decidability results extend to these models.     

A flow measurement architecture to preserve application structure

The Internet has significantly evolved in the number and variety of applications. Network operators need mechanisms to constantly monitor and study these applications. Modern routers employ passive measurement solution called Sampled NetFlow to collect basic statistics on a per-flow basis (for a small subset of flows), that could provide valuable information for application monitoring. Given modern applications routinely consist of several flows, potentially to many different destinations, only a few flows are sampled per application session using Sampled NetFlow. To address this issue, in this paper, we introduce related sampling that allows network operators to give a higher probability to flows that are part of the same application session. Given the lack of application semantics in the middle of the network, our architecture, RelSamp, treats flows that share the same source IP address as related. Our heuristic works well in practice as hosts typically run few applications at any given instant, as observed using a measurement study on real traces. In our evaluation using real traces, we show that RelSamp achieves 5–10× more flows per application session compared to Sampled NetFlow for the same effective number of sampled packets. We also show that behavioral and statistical classification approaches such as BLINC, SVM and C4.5 achieve up to 50% better classification accuracy compared to Sampled NetFlow, while not impairing existing management tasks such as volume estimation too much.     

Public key distribution scheme for delay tolerant networks based on two-channel cryptography

A delay tolerant network (DTN) is a store carry and forward network characterized by highly mobile nodes, intermittent connectivity with frequent disruptions, limited radio range and physical obstructions. Emerging applications of DTN include rural DTN, vehicular DTN and pocket DTN. The development of DTN raises a number of security-related challenges due to inconsistent network access and unreliable end-to-end network path. One of the challenges is initial secure context establishment as it is unrealistic to assume that public key infrastructure (PKI) is always globally present and available, hence, the public key management becomes an open problem for DTN. In this paper, for the first time, we propose a dynamic virtual digraph (DVD) model for public key distribution study by extending graph theory and then present a public key distribution scheme for pocket DTN based on two-channel cryptography. By distinguishing between owners and carriers, public key exchange and authentication issues in the decentralized pocket DTN environment can be solved by a two-channel cryptography process and our simulation results have proven it.