Showing papers on "Routing (electronic design automation) published in 2007"

Connectivity-Aware Routing (CAR) in Vehicular Ad-hoc Networks

Abstract: Vehicular ad hoc networks using WLAN technology have recently received considerable attention. We present a position-based routing scheme called Connectivity-Aware Routing (CAR) designed specifically for inter-vehicle communication in a city and/or highway environment. A distinguishing property of CAR is the ability to not only locate positions of destinations but also to find connected paths between source and destination pairs. These paths are auto-adjusted on the fly, without a new discovery process. "Guards" help to track the current position of a destination, even if it traveled a substantial distance from its initially known location. For the evaluation of the CAR protocol we use realistic mobility traces obtained from a microscopic vehicular traffic simulator that is based on a model of driver behavior and the real road maps of Switzerland.

Flattened butterfly: a cost-efficient topology for high-radix networks

Abstract: Increasing integrated-circuit pin bandwidth has motivateda corresponding increase in the degree or radix of interconnection networksand their routers. This paper introduces the flattened butterfly, a cost-efficient topology for high-radix networks. On benign (load-balanced) traffic, the flattened butterfly approaches the cost/performance of a butterfly network and has roughly half the cost of a comparable performance Clos network.The advantage over the Clos is achieved by eliminating redundant hopswhen they are not needed for load balance. On adversarial traffic, the flattened butterfly matches the cost/performance of a folded-Clos network and provides an order of magnitude better performance than a conventional butterfly.In this case, global adaptive routing is used to switchthe flattened butterfly from minimal to non-minimal routing - usingredundant hops only when they are needed. Minimal and non-minimal, oblivious and adaptive routing algorithms are evaluated on the flattened butterfly.We show that load-balancing adversarial traffic requires non-minimalglobally-adaptive routing and show that sequential allocators are required to avoid transient load imbalance when using adaptive routing algorithms.We also compare the cost of the flattened butterfly to folded-Clos, hypercube,and butterfly networks with identical capacityand show that the flattened butterfly is more cost-efficient thanfolded-Clos and hypercube topologies.

Printed Circuits Handbook

Abstract: Interconnectivity component packages printed circuits surface mount technology multichip module technology basic board materials specialized board materials electrical and mechanical design computer aided design computer simulations of design parameters fine line technologies image transfer drilling etching electroplating additive plating routing and machining multilayer processes solder mask testing small quantity assembly automated assembly solder basics soldering basics no-clean processes solderability standards and testing assembly testing repair of bare board and board assemblies waste minimalization waste treatment and disposal quality programmes acceptability of printed circuit boards and assemblies reliability of printed circuit boards vendor selection and development flexible circuit materials and fabrication.

System and method for routing data on a packet network

Abstract: The disclosed embodiments include system and method for routing communications over a communications network. In one embodiment, a determination is made as to whether to establish a communication along a communication path based on network performance information. The disclosed embodiments provide several alternatives for establishing the communication and improving communications along the communication path in response to a determination that at least one network node along the communication path is impaired or congested.

DTN routing as a resource allocation problem

Abstract: Many DTN routing protocols use a variety of mechanisms, including discovering the meeting probabilities among nodes, packet replication, and network coding. The primary focus of these mechanisms is...

Trading structure for randomness in wireless opportunistic routing

Abstract: Opportunistic routing is a recent technique that achieves high throughput in the face of lossy wireless links. The current opportunistic routing protocol, ExOR, ties the MAC with routing, imposing ...

Modeling Time-Variant User Mobility in Wireless Mobile Networks

Abstract: Realistic mobility models are important to understand the performance of routing protocols in wireless ad hoc networks, especially when mobility-assisted routing schemes are employed, which is the case, for example, in delay-tolerant networks (DTNs). In mobility-assisted routing, messages are stored in mobile nodes and carried across the network with nodal mobility. Hence, the delay involved in message delivery is tightly coupled with the properties of nodal mobility. Currently, commonly used mobility models are simplistic random i.i.d. model that do not reflect realistic mobility characteristics. In this paper we propose a novel time-variant community mobility model. In this model, we define communities that are visited often by the nodes to capture skewed location visiting preferences, and use time periods with different mobility parameters to create periodical re-appearance of nodes at the same location. We have clearly observed these two properties based on analysis of empirical WLAN traces. In addition to the proposal of a realistic mobility model, we derive analytical expressions to highlight the impact on the hitting time and meeting times if these mobility characteristics are incorporated. These quantities in turn determine the packet delivery delay in mobility-assisted routing settings. Simulation studies show our expressions have error always under 20%, and in 80% of studied cases under 10%.

Processor Design in 3D Die-Stacking Technologies

Abstract: Three-dimensional integration is an emerging fabrication technology that vertically stacks multiple integrated chips. The benefits include an increase in device density; much greater flexibility in routing signals, power, and clock; the ability to integrate disparate technologies; and the potential for new 3D circuit and microarchitecture organizations. This article provides a technical introduction to the technology and its impact on processor design. Although our discussions here primarily focus on high-performance processor design, most of the observations and conclusions apply to other microprocessor market segments.

An Exact Approach for the Vehicle Routing Problem with Two-Dimensional Loading Constraints

Abstract: We consider a special case of the symmetric capacitated vehicle routing problem, in which a fleet of K identical vehicles must serve n customers, each with a given demand consisting in a set of rectangular two-dimensional weighted items. The vehicles have a two-dimensional loading surface and a maximum weight capacity. The aim is to find a partition of the customers into routes of minimum total cost such that, for each vehicle, the weight capacity is taken into account and a feasible two-dimensional allocation of the items into the loading surface exists. The problem has several practical applications in freight transportation, and it is NP-hard in the strong sense. We propose an exact approach, based on a branch-and-cut algorithm, for the minimization of the routing cost that iteratively calls a branch-and-bound algorithm for checking the feasibility of the loadings. Heuristics are also used to improve the overall performance of the algorithm. The effectiveness of the approach is shown by means of computational results.

Cooperative Routing in Static Wireless Networks

Abstract: We study the problem of transmission-side diversity and routing in a static wireless network. It is assumed that each node in the network is equipped with a single omnidirectional antenna and that multiple nodes are allowed to coordinate their transmissions in order to obtain energy savings. We derive analytical results for achievable energy savings for both line and grid network topologies. It is shown that the energy savings of and are achievable in line and grid networks with a large number of nodes, respectively. We then develop a dynamic-programming-based algorithm for finding the optimal route in an arbitrary network, as well as suboptimal algorithms with polynomial complexity. We show through simulations that these algorithms can achieve average energy savings of about in random networks, as compared to the noncooperative schemes.

Fast Routing in Road Networks with Transit Nodes

Abstract: When you drive to somewhere far away, you will leave your current location via one of only a few important traffic junctions. Starting from this informal observation, we developed an algorithmic approach, transit node routing, that allows us to reduce quickest path queries in road networks to a small number of table lookups. For road maps of Western Europe and the United States, our best query times improved over the best previously published figures by two orders of magnitude. This is also more than one million times faster than the best known algorithm for general networks.

Solving the Capacitated Location-Routing Problem by a Cooperative Lagrangean Relaxation-Granular Tabu Search Heuristic

Abstract: Most of the time in a distribution system, depot location and vehicle routing are interdependent, and recent studies have shown that the overall system cost may be excessive if routing decisions are ignored when locating depots. The location-routing problem (LRP) overcomes this drawback by simultaneously tackling location and routing decisions. This paper presents a cooperative metaheuristic to solve the LRP with capacitated routes and depots. The principle is to alternate between a depot location phase and a routing phase, exchanging information on the most promising edges. In the first phase, the routes and their customers are aggregated into supercustomers, leading to a facility-location problem, which is then solved by a Lagrangean relaxation of the assignment constraints. In the second phase, the routes from the resulting multidepot vehicle-routing problem (VRP) are improved using a granular tabu search (GTS) heuristic. At the end of each global iteration, information about the edges most often used is recorded to be used in the following phases. The method is evaluated on three sets of randomly generated instances and compared with other heuristics and a lower bound. Solutions are obtained in a reasonable amount of time for such a strategic problem and show that this metaheuristic outperforms other methods on various kinds of instances.

Enhanced Perimeter Routing for Geographic Forwarding Protocols in Urban Vehicular Scenarios

Abstract: Geographic stateless routing schemes such as GPSR have been widely adopted to routing in vehicular ad hoc networks (VANET). However, due to the particular urban topology and the non-uniform distribution of cars, the greedy routing mode often fails and needs a recovery strategy such as GPSR's perimeter mode to deliver data successfully to the destination. It has been shown that the cost of planarization, the non-uniform distribution of cars, and radio obstacles make GPSR's perimeter mode inefficient in urban configurations. Some enhancements have been proposed such as GPCR, which uses the concept of junction nodes to control the next road segments that packets should follow. However, the concept of junction nodes itself is problematic and hard to maintain in a dynamic urban environment. In this paper, we describe GpsrJ+, a solution that further improves the packet delivery ratio of GPCR with minimal modification by predicting on which road segment its neighboring junction node will forward packets to. GpsrJ+ differs from GPCR as decisions about which road segment to turn does not need to be made by junction nodes. Moreover, GpsrJ+ does not need an expensive planarization strategy since it uses the natural planar feature of urban maps. Consequently, GpsrJ+ reduces the hop count used in the perimeter mode by as much as 200% compared to GPSR. It therefore allows geographic routing schemes to return to the greedy mode faster.

Achieving convergence-free routing using failure-carrying packets

Abstract: Current distributed routing paradigms (such as link-state, distance-vector, and path-vector) involve a convergence process consisting of an iterative exploration of intermediate routes triggered by certain events such as link failures. The convergence process increases router load, introduces outages and transient loops, and slows reaction to failures. We propose a new routing paradigm where the goal is not to reduce the convergence times but rather to eliminate the convergence process completely. To this end, we propose a technique called Failure-Carrying Packets (FCP) that allows data packets to autonomously discover a working path without requiring completely up-to-date state in routers. Our simulations, performed using real-world failure traces and Rocketfuel topologies, show that: (a) the overhead of FCP is very low, (b) unlike traditional link-state routing (such as OSPF), FCP can provide both low loss-rate as well as low control overhead, (c) compared to prior work in backup path pre-computations, FCP provides better routing guarantees under failures despite maintaining lesser state at the routers.

Flexible job-shop scheduling with routing flexibility and separable setup times using ant colony optimisation method

Abstract: This paper proposes an ant colony optimisation-based software system for solving FMS scheduling in a job-shop environment with routing flexibility, sequence-dependent setup and transportation time. In particular, the optimisation problem for a real environment, including parallel machines and operation lag times, has been approached by means of an effective pheromone trail coding and tailored ant colony operators for improving solution quality. The method used to tune the system parameters is also described. The algorithm has been tested by using standard benchmarks and problems, properly designed for a typical FMS layout. The effectiveness of the proposed system has been verified in comparison with alternative approaches.

Media management and routing within an electronic device

Abstract: A method and apparatus for intelligently routing and managing audio signals within an electronic device is disclosed. The routing is responsive to a set of logical and physical policies which are stored in data tables which can be updated as needed.

Discrete Optimization An exact algorithm for a single-vehicle routing problem with time windows and multiple routes

Abstract: This paper describes an exact algorithm for solving a problem where the same vehicle performs several routes to serve a set of customers with time windows. The motivation comes from the home delivery of perishable goods, where vehicle routes are short and must be combined to form a working day. A method based on an elementary shortest path algorithm with resource constraints is proposed to solve this problem. The method is divided into two phases: in the first phase, all non-dominated feasible routes are generated; in the second phase, some routes are selected and sequenced to form the vehicle workday. Computational results are reported on Euclidean problems derived from benchmark instances of the classical vehicle routing problem with time windows. � 2006 Elsevier B.V. All rights reserved.

NetDiagnoser: troubleshooting network unreachabilities using end-to-end probes and routing data

Abstract: The distributed nature of the Internet makes it difficult for a single service provider to troubleshoot the disruptions experienced by its customers. We propose NetDiagnoser, a troubleshooting algorithm to identify the location of failures in an internetwork environment. First, we adapt the well-known Boolean tomography technique to work in this environment. Then, we significantly extend this technique to improve the diagnosis accuracy in the presence of multiple link failures, logical failures (for instance, misconfigurations of route export filters), and incomplete topology inference. In particular, NetDiagnoser takes advantage of rerouted paths, routing messages collected at one provider's network and Looking Glass servers. We evaluate each feature of Net-Diagnoser separately using C-BGP simulations on realistic topologies. Our results show that NetDiagnoser can successfully identify a small set of links, which almost always includes the actually failed/misconfigured links.

Genetic Algorithm for Energy Efficient Clusters in Wireless Sensor Networks

Abstract: We use a genetic algorithm (GA) to create energy efficient clusters for routing in wireless sensor networks. The simulation results show that the proposed intelligent hierarchical clustering technique is more energy efficient than a few existing cluster-based routing protocols. Further, the gradual energy depletion in sensor nodes is also investigated

Dynamic vehicle routing using genetic algorithms

Abstract: Many difficult combinatorial optimization problems have been modeled as static problems. However, in practice, many problems are dynamic and changing, while some decisions have to be made before all the design data are known. For example, in the Dynamic Vehicle Routing Problem (DVRP), new customer orders appear over time, and new routes must be reconfigured while executing the current solution. Montemanni et al. [1] considered a DVRP as an extension to the standard vehicle routing problem (VRP) by decomposing a DVRP as a sequence of static VRPs, and then solving them with an ant colony system (ACS) algorithm. This paper presents a genetic algorithm (GA) methodology for providing solutions for the DVRP model employed in [1]. The effectiveness of the proposed GA is evaluated using a set of benchmarks found in the literature. Compared with a tabu search approach implemented herein and the aforementioned ACS, the proposed GA methodology performs better in minimizing travel costs.

Methods and systems for placement and routing

Abstract: Techniques for placement of integrated circuit elements include global placement, detailed placement, timing closure, and routing. The integrated circuit is described by a netlist specifying interconnections of morphable devices. The detailed placement uses, for example, Simultaneous Dynamical Integration, wherein the morphable-devices correspond to nodes influenced by forces, including timing forces. The timing forces are derived, for example, from a timing graph; path delay; slack; and drive resistance of the elements. The timing closure uses timing-driven buffering and timing-driven resizing to reduce maximum delay and/or transition time, and/or to fix hold time. Nets having high capacitance and/or fanout, and timing critical nets are preferentially processed. Timing-driven buffering applies buffering solutions to segments of route trees, combines solutions of adjoining segments, and prunes sets of solutions. Timing-driven resizing morphably replaces selected elements with upsized versions thereof.