Modeling and distributed simulation of a broadband-ISDN network

A distributed approach to communication network simulation using a network of workstations configured as a loosely coupled parallel processor to model and simulate the broadband integrated services digital network (B-ISDN) is proposed. In a loosely coupled parallel processor system, a number of concurrently executable processors communicate asynchronously using explicit messages over high-speed links. Since this architecture is similar to that of B-ISDN networks, it constitutes a realistic testbed for their modeling and simulation. The authors describe an implementation of this approach on 50 Sun workstations at Brown University. Performance results, based on representative B-ISDN networks and realistic traffic models, indicate that the distributed approach is efficient and accurate     

A flexible communications protocol for a distributed surveillance system

On-line surveillance for safety and security is a major requirement of public transport and other public places to address the modern demands of mobility in major urban areas and to effect improvements in quality of life and environment protection. The surveillance task is a complex one involving technology, management procedures and people. Visual surveillance based on Closed Circuit Television system is an important part of such systems, but visual processing is not sufficient and the geographical distribution of devices and management has to be taken into account. In this paper we present a surveillance architecture that reflects the distributed nature of the monitoring task and allows for distributed detection processes, not only dealing with visual processing but also with devices such as acoustic signature detection and mobile smart cards, actuators and a range of other possible sensors. The design uses ideas from control engineering and distributed communications networks resulting in a communications architecture based on CORBA and XML messaging. We have shown how to define a generic device/sensor model appropriate for the surveillance task and sufficiently flexible so as to allow for scalability, expansion and customisation of a practical surveillance task. The paper gives sufficient details on the protocols to show how intelligent detection modules can be integrated as part of this kind of system. The system components have been implemented and integrated in two major successful trials in metropolitan railway stations in London and in Paris, as part of a major EU-funded project (PRISMATICA).     

Control program for a microcomputer network

The network-operating system described in the paper consists of masters running MP/M and slaves running CP/M. Several configurations of CP/net, CP/M and MP/M are described, along with the CP/net capabilities and message format. The slave configuration is defined and the network interface processes are discussed.     

A virtual cockpit for a distributed interactive simulation

We developed the virtual cockpit as an inexpensive flight simulator, using off-the-shelf equipment. This system functions as a component of a distributed interactive simulation. Any flight simulator has three principal tasks: image display, image generation, and flight dynamics. We built the flight simulator, the virtual cockpit, using a head-mounted display (HMD) to display the out-the-window imagery and the cockpit interior. The virtual cockpit consists of a Silicon Graphics workstation and supporting hardware components, such as an HMD and position tracker. The software falls into three areas by function: flight dynamics and cockpit instruments; network interface (either SimNet or DIS PDUs); and display of the out-the-window view. The virtual cockpit developed uses a multiprocessor Silicon Graphics Iris (the 4D/440VGXT) connected to a Polhemus Laboratories fiber-optic head-mounted display, a Polhemus magnetic head tracker and a hands-on-throttle-and-stick (HOTAS) by Thrustmaster. The software uses the AT and T C++ translator and the Silicon Graphics C compiler running under Irix 4.0.5. a Unix operating system. We use Software Systems' MultiGen to create the geometric models and the terrain database     

A faster distributed protocol for constructing a minimum spanning tree

This paper studies the problem of constructing a minimum-weight spanning tree (MST) in a distributed network. This is one of the most important problems in the area of distributed computing. There is a long line of gradually improving protocols for this problem, and the state of the art today is a protocol with running time due to Kutten and Peleg [S. Kutten, D. Peleg, Fast distributed construction of k-dominating sets and applications, J. Algorithms 28 (1998) 40-66; preliminary version appeared in: Proc. of 14th ACM Symp. on Principles of Distributed Computing, Ottawa, Canada, August 1995, pp. 20-27], where Λ(G) denotes the diameter of the graph G. Peleg and Rubinovich [D. Peleg, V. Rubinovich, A near-tight lower bound on the time complexity of distributed MST construction, in: Proc. 40th IEEE Symp. on Foundations of Computer Science, 1999, pp. 253-261] have shown that time is required for constructing MST even on graphs of small diameter, and claimed that their result “establishes the asymptotic near-optimality” of the protocol of [S. Kutten, D. Peleg, Fast distributed construction of k-dominating sets and applications, J. Algorithms 28 (1998) 40-66; preliminary version appeared in: Proc. of 14th ACM Symp. on Principles of Distributed Computing, Ottawa, Canada, August 1995, pp. 20-27].In this paper we refine this claim, and devise a protocol that constructs the MST in rounds, where μ(G,ω) is the MST-radius of the graph. The ratio between the diameter and the MST-radius may be as large as Θ(n), and, consequently, on some inputs our protocol is faster than the protocol of [S. Kutten, D. Peleg, Fast distributed construction of k-dominating sets and applications, J. Algorithms 28 (1998) 40-66; preliminary version appeared in: Proc. of 14th ACM Symp. on Principles of Distributed Computing, Ottawa, Canada, August 1995, pp. 20-27] by a factor of . Also, on every input, the running time of our protocol is never greater than twice the running time of the protocol of [S. Kutten, D. Peleg, Fast distributed construction of k-dominating sets and applications, J. Algorithms 28 (1998) 40-66; preliminary version appeared in: Proc. of 14th ACM Symp. on Principles of Distributed Computing, Ottawa, Canada, August 1995, pp. 20-27].As part of our protocol for constructing an MST, we develop a protocol for constructing neighborhood covers with a drastically improved running time. The latter result may be of independent interest.     

A distributed shortest path algorithm for a planar network

An algorithm is presented for finding a single source shortest path tree in a planar undirected distributed network with nonnegative edge costs. The number of messages used by the algorithm is O(n^5/3) on an n-node network. Distributed algorithms are also presented for finding a breath-first spanning tree in general network, for finding a shortest path tree in a general network, for finding a separator of a planar network, and for finding a division of a planar network.     

A time-optimal distributed sorting algorithm on a line network

We have achieved a strict lower time bound of n−1 for distributed sorting on a line network, where n is the number of processes. The lower time bound has traditionally been considered to be n because it is proved based on the number of disjoint comparison-exchange operations in parallel sorting on a linear array. Our result has overthrown the traditional common belief.     

A microcomputer program for second-order simulation of EPR spectra

A program for second-order simulation of isotropic EPR spectra has been developed for a microcomputer Apple II Plus. The programming is done in UCSD Pascal language. A recursion algorithm is developed for nuclear spin I < 0.5. Some applications of second-order simulations are calculated and discussed.     

A communication system for distributed computations on a network of personal computers

This paper deals with a software system PCCOM which makes it possible to simulate a distributed memory environment for parallel computations by using a local area network of personal computers. This system consists of FORTRAN subroutines that can be used from application programs. Parallel computations may be performed on a network of personal computers under DOS or any other operating system. This software package simulates, partially, the widespread PVM (Parallel Virtual Machine) package which runs under UNIX. A simple example of an application is given here.     

A distributed QoS-Aware multicast routing protocol

This paper discusses the multicast routing problem with QoS constraints, and describes a network model that is suitable to research such routing problem. The paper mainly presents a distributed QoS-aware multicast routing protocol (QMRP). The QMRP can operate on top of the unicast routing protocol. It only requires the local state information of the link (or the node), but does not require any global network state to be maintained. The QMRP can significantly reduce the overhead for constructing a multicast tree with QoS constraints. In QMRP, a multicast group member can join or leave the multicast session dynamically, which can support dynamic membership. The protocol can search multiple feasible tree branches, and select the optimal or near-optimal branch for connecting the new receiver to the multicast tree if it exists. In this paper, the proof of correctness and complexity analysis of the QMRP are given, and the performance measures of the protocol are evaluated using simulation. The study shows that QMRP provides an available approach to multicast routing with QoS constraints and dynamic membership support.Received: 3 April 2003, Published online: 2 September 2003     

Visual interactive simulation using a microcomputer

The paper describes an approach to discrete event simulation in which the status of a model is dynamically displayed on a graphics screen. The end user may watch and interact with the model in order to try alternative strategies. The paper reports that the visual interactive technique, if used on a time sharing computer suffers due to variable response times and that the implementation using a microcomputer gives a feasible alternative.     

A queueing network model for a distributed database testbed system

A queuing network model for analyzing the performance of a distributed database testbed system with a transaction workload is developed. The model includes the effects of the concurrency control protocol (two-phase locking with distributed deadlock detection), the transaction recovery protocol (write-ahead logging of before-images), and the commit protocol (centralized two-phase commit) used in the testbed system. The queuing model differs from previous analytical models in three major aspects. First, it is a model for a distributed transaction processing system. Second, it is more general and integrated than previous analytical models. Finally, it reflects a functioning distributed database testbed system and is validated against performance measurements     

A distributed semantic network model for a collaborative intelligent system

A methodology based on topology theory to model a semantic network for a collaborative system is given. This framework is used to support the creation of a semantic network and to define the associated intelligent cooperative system. Our methodology is illustrated via a set of agents whose knowledge-base is a semantic network. By a series of functions applied on a base of entities, issued from the application domain, a family of sets are synthesized with their subspaces correlated. The resultant subspaces and their relations form a network of elementary and complex concepts that can be naturally represented with the IDEF1x language. A prototype Multi-Agent System (MAS), set up with the Zeus platform,¹ was developed for the Process Plan domain, which was used as a case study. Full correspondence among the subspaces, the semantic network IDEF1x information model and the MAS implementation is obtained by employing this framework.     

A distributed energy-efficient clustering protocol for wireless sensor networks

Minimizing energy dissipation and maximizing network lifetime are among the central concerns when designing applications and protocols for sensor networks. Clustering has been proven to be energy-efficient in sensor networks since data routing and relaying are only operated by cluster heads. Besides, cluster heads can process, filter and aggregate data sent by cluster members, thus reducing network load and alleviating the bandwidth. In this paper, we propose a novel distributed clustering algorithm where cluster heads are elected following a three-way message exchange between each sensor and its neighbors. Sensor’s eligibility to be elected cluster head is based on its residual energy and its degree. Our protocol has a message exchange complexity of O(1) and a worst-case convergence time complexity of O(N). Simulations show that our algorithm outperforms EESH, one of the most recently published distributed clustering algorithms, in terms of network lifetime and ratio of elected cluster heads.     

一种分布式能量高效的WSNs非均匀分簇路由协议

针对无线传感器网络(WSNs)多跳通信方式中存在的"热区"问题,提出了一种分布式的、能量高效的非均匀分簇(DEEUC)路由协议。该协议将节点的剩余能量作为簇首选择的一个重要指标,候选簇首由上轮簇首根据簇内成员节点的剩余能量指定,候选簇首能否最终成簇首也是其能量竞争的结果。在DEEUC协议中,簇首以多跳的方式与基站进行通信并选择正向单位能耗最小的邻居簇首作为路由节点以节约能耗。仿真实验表明:DEEUC能较好地提高网络能效,延长网络生存时间。     

A presentation protocol for videotex network systems

The environment, motivations and design concepts which lead to the development of this presentation level protocol have produced an application-independent protocol. As an introduction to the basic components of a network presentation protocol, explanations of a presentation image, commands, and presentation image-definition and how to use them to their best advantage are given. A specific example of a presentation image for videotex systems demonstrates the protocol's feasibility, usefulness, and simplicity.     

Evaluating a new communication protocol for real-time distributed control

The recent trend in distributed automation and control systems has been towards event-triggered system architectures such as UML and IEC 61499. Although existing communication protocols (e.g., Ethernet) can support high-level communication within these systems, there is contention as to which low-level protocol to use, or if any exist that meet the requirements of being event-triggered and hard real-time. This paper proposes a new way to measure communication performance. The goal of the new measurement method is to stress the necessity that a real-time communication protocol needs to be both efficient and fair. This is illustrated by comparing three communication strategies: Controller Area Network (CAN), Time-Triggered CAN (TTCAN) and Escalating Priority CAN (EPCAN). The first two represent the extremes between event-triggered and time-triggered communication strategies; the third is introduced to illustrate the benefits of a new event-based communication protocol proposed by the authors.     

无线自组网多播协议的设计与仿真

在Ad hoc网络中,为了平衡能耗与鲁棒性,结合基于树和基于网格的多播协议的特点,给出了一个新的多播路由协议,基于Power aware优化的备用路径的多播协议(power aware-backup tree multicast,Pa-BTM).该协议采用主树和备用树相结合使用的方法,当主树损坏后立即采用备用树进行工作,提高了鲁棒性,同时基于树的结构也减少了能量的消耗.最后,使用仿真工具GloMosim对MAODV,ODMRP及Pa-BTM模拟仿真.仿真结果表明,该协议在包分发率和能量效能等性能上有所改善,可以较好地提高网络生存时间.