Showing papers on "Routing (electronic design automation) published in 2004"

On A Routing Problem

Abstract: In a system with one queue and several service stations, it is a natural principle to route a customer to the idle station with the distributionwise shortest service time. For the case with exponentially distributed service times, we use a coupling to give strong support to that principle. We also treat another topic. A modified version of our methods brings support to the design principle: It is better with few but quick servers.

Bandwidth-constrained mapping of cores onto NoC architectures

Abstract: We address the design of complex monolithic systems, where processing cores generate and consume a varying and large amount of data, thus bringing the communication links to the edge of congestion. Typical applications are in the area of multi-media processing. We consider a mesh-based networks on chip (NoC) architecture, and we explore the assignment of cores to mesh cross-points so that the traffic on links satisfies bandwidth constraints. A single-path deterministic routing between the cores places high bandwidth demands on the links. The bandwidth requirements can be significantly reduced by splitting the traffic between the cores across multiple paths. In this paper, we present NMAP, a fast algorithm that maps the cores onto a mesh NoC architecture under bandwidth constraints, minimizing the average communication delay. The NMAP algorithm is presented for both single minimum-path routing and split-traffic routing. The algorithm is applied to a benchmark DSP design and the resulting NoC is built and simulated at cycle accurate level in SystemC using macros from the /spl times/pipes library. Also, experiments with six video processing applications show significant savings in bandwidth and communication cost for NMAP algorithm when compared to existing algorithms.

Simultaneous routing and resource allocation via dual decomposition

Abstract: In wireless data networks, the optimal routing of data depends on the link capacities which, in turn, are determined by the allocation of communications resources (such as transmit powers and bandwidths) to the links. The optimal performance of the network can only be achieved by simultaneous optimization of routing and resource allocation. In this paper, we formulate the simultaneous routing and resource allocation (SRRA) problem, and exploit problem structure to derive efficient solution methods. We use a capacitated multicommodity flow model to describe the data flows in the network. We assume that the capacity of a wireless link is a concave and increasing function of the communications resources allocated to the link, and the communications resources for groups of links are limited. These assumptions allow us to formulate the SRRA problem as a convex optimization problem over the network flow variables and the communications variables. These two sets of variables are coupled only through the link capacity constraints. We exploit this separable structure by dual decomposition. The resulting solution method attains the optimal coordination of data routing in the network layer and resource allocation in the radio control layer via pricing on the link capacities.

An extended localized algorithm for connected dominating set formation in ad hoc wireless networks

Abstract: Efficient routing among a set of mobile hosts is one of the most important functions in ad hoc wireless networks. Routing based on a connected dominating set is a promising approach, where the search space for a route is reduced to the hosts in the set. A set is dominating if all the hosts in the system are either in the set or neighbors of hosts in the set. The efficiency of dominating-set-based routing mainly depends on the overhead introduced in the formation of the dominating set and the size of the dominating set. In this paper, we first review a localized formation of a connected dominating set called marking process and dominating-set-based routing. Then, we propose a dominant pruning rule to reduce the size of the dominating set. This dominant pruning rule (called Rule k) is a generalization of two existing rules (called Rule 1 and Rule 2, respectively). We prove that the vertex set derived by applying Rule k is still a connected dominating set. Rule k is more effective in reducing the dominating set derived from the marking process than the combination of Rules 1 and 2 and, surprisingly, in a restricted implementation with local neighborhood information, Rule k has the same communication complexity and less computation complexity. Simulation results confirm that Rule k outperforms Rules 1 and 2, especially in networks with relatively high vertex degree and high percentage of unidirectional links. We also prove that an upper bound exists on the average size of the dominating set derived from Rule k in its restricted implementation.

Locating and bypassing routing holes in sensor networks

Abstract: Many algorithms for routing in sensor networks exploit greedy forwarding strategies to get packets to their destinations. We study a fundamental difficulty such strategies face: the "local minimum phenomena" that can cause packets to get stuck. We give a definition of stuck nodes where packets may get stuck in greedy multi-hop forwarding, and develop a local rule, the TENT rule, for each node in the network to test whether a packet can get stuck at that node. To help the packets get out of stuck nodes, we describe a distributed algorithm, BOUNDHOLE, to build routes around holes, which are connected regions of the network with boundaries consisting of all the stuck nodes. We show that these hole-surrounding routes can be used in many applications such as geographic routing, path migration, information storage mechanisms and identification of regions of interest.

Scenario-Based Planning for Partially Dynamic Vehicle Routing with Stochastic Customers

Abstract: The multiple vehicle routing problem with time windows (VRPTW) is a hard and extensively studied combinatorial optimization problem. This paper considers a dynamic VRPTW with stochastic customers, where the goal is to maximize the number of serviced customers. It presents a multiple scenario approach (MSA) that continuously generates routing plans for scenarios including known and future requests. Decisions during execution use a distinguished plan chosen, at each decision, by a consensus function. The approach was evaluated on vehicle routing problems adapted from the Solomon benchmarks with a degree of dynamism varying between 30% and 80%. They indicate that MSA exhibits dramatic improvements over approaches not exploiting stochastic information, that the use of consensus function improves the quality of the solutions significantly, and that the benefits of MSA increase with the (effective) degree of dynamism.

ACE: An Emergent Algorithm for Highly Uniform Cluster Formation

Abstract: The efficient subdivision of a sensor network into uniform, mostly non-overlapping clusters of physically close nodes is an important building block in the design of efficient upper layer network functions such as routing, broadcast, data aggregation, and query processing.

A Two-Stage Hybrid Local Search for the Vehicle Routing Problem with Time Windows

Abstract: The vehicle routing problem with time windows is a hard combinatorial optimization problem that has received considerable attention in the last decades. This paper proposes a two-stage hybrid algorithm for this transportation problem. The algorithm first minimizes the number of vehicles, using simulated annealing. It then minimizes travel cost by using a large neighborhood search that may relocate a large number of customers. Experimental results demonstrate the effectiveness of the algorithm, which has improved 10 (17%) of the 56 best published solutions to the Solomon benchmarks, while matching or improving the best solutions in 46 problems (82%). More important perhaps, the algorithm is shown to be very robust. With a fixed configuration of its parameters, it returns either the best published solutions (or improvements thereof) or solutions very close in quality on all Solomon benchmarks. Very preliminary results on the extended Solomon benchmarks are also given.

Routing in a delay tolerant network

Abstract: We formulate the delay-tolerant networking routing problem, where messages are to be moved end-to-end across a connectivity graph that is time-varying but whose dynamics may be known in advance. Th...

Intelligent well system and method

Abstract: An intelligent well system and method has a sand face completion and a monitoring system to monitor application of a well operation. Various equipment and services may be used. In another aspect, the invention provides a monitoring system for determining placement of a well treatment. Yet another aspect of the invention is an instrumented sand screen. Another aspect is a connector for routing control lines.

Comparison of routing metrics for static multi-hop wireless networks

Abstract: Routing protocols for wireless ad hoc networks have traditionally focused on finding paths with minimum hop count. However, such paths can include slow or lossy links, leading to poor throughput. A...

On the Computational Complexity of Sensor Network Localization

Abstract: Determining the positions of the sensor nodes in a network is essential to many network functionalities such as routing, coverage and tracking, and event detection. The localization problem for sensor networks is to reconstruct the positions of all of the sensors in a network, given the distances between all pairs of sensors that are within some radius r of each other. In the past few years, many algorithms for solving the localization problem were proposed, without knowing the computational complexity of the problem. In this paper, we show that no polynomial-time algorithm can solve this problem in the worst case, even for sets of distance pairs for which a unique solution exists, unless RP = NP. We also discuss the consequences of our result and present open problems.

Hierarchical location service for mobile ad-hoc networks

Abstract: Position-based routing has proven to be a scalable and efficient way for packet routing in mobile ad-hoc networks To enable position-based routing, a node must be able to discover the location of the node it wants to communicate with This task is typically accomplished by a location service In this paper, we propose a novel location service called HLS (Hierarchical Location Service) HLS divides the area covered by the network into a hierarchy of regions The top level region covers the complete network A region is subdivided into several regions of the next lower level until the lowest level is reached We call a lowest level region a cell For a given node A, one specific cell is selected on each level of the hierarchy by means of hash function As A changes its position it transmits position updates to these responsible cells If another node wants to determine the position of A it uses the same hash function to determine the cells that may hold information about the position of A It then proceeds to query the nodes in these cells in the order of the hierarchy until it receives a reply containing the current position of A Because of its hierarchical approach HLS is highly scalable and particularly well suited for networks where communication partners tend to be close to each other Due to the inherent scaling limitations of ad-hoc networks it is very likely that most ad hoc networks will display this property Furthermore HLS is very robust to node mobility and node failures since it uses regions to select location servers and not a chain of mobile nodes as it is the case, eg, for the well known Grid Location Service (GLS) We demonstrate these traits by providing extensive simulation data on the behaviour of HLS in a wide range of scenarios and by using GLS as a benchmark

On Customer Contact Centers with a Call-Back Option: Customer Decisions, Routing Rules, and System Design

Abstract: Organizations worldwide use contact centers as an important channel of communication and transaction with their customers. This paper describes a contact center with two channels, one for real-time telephone service, and another for a postponed call-back service offered with a guarantee on the maximum delay until a reply is received. Customers are sensitive to both real-time and call-back delay and their behavior is captured through a probabilistic choice model. The dynamics of the system are modeled as anM/M/N multiclass system. We rigorously justify that as the number of agents increases, the system's load approaches its maximum processing capacity. Based on this observation, we perform an asymptotic analysis in the many-server, heavy traffic regime to find an asymptotically optimal routing rule, characterize the unique equilibrium regime of the system, approximate the system performance, and finally, propose a staffing rule that picks the minimum number of agents that satisfies a set of operational constraints on the performance of the system.

Dynamic Programming Approximations for a Stochastic Inventory Routing Problem

Abstract: This work is motivated by the need to solve the inventory routing problem when implementing a business practice called vendor managed inventory replenishment (VMI). With VMI, vendors monitor their customers' inventories and decide when and how much inventory should be replenished at each customer. The inventory routing problem attempts to coordinate inventory replenishment and transportation in such a way that the cost is minimized over the long run. We formulate a Markov decision process model of the stochastic inventory routing problem and propose approximation methods to find good solutions with reasonable computational effort. We indicate how the proposed approach can be used for other Markov decision processes involving the control of multiple resources.

Link-level measurements from an 802.11b mesh network

Abstract: This paper analyzes the causes of packet loss in a 38-node urban multi-hop 802.11b network. The patterns and causes of loss are important in the design of routing and error-correction protocols, as...

CMOS-like logic in defective, nanoscale crossbars

Abstract: We present an approach to building defect-tolerant, nanoscale compute fabrics out of assemblies of defective crossbars of configurable FETs and switches. The simplest structure, the complementary/symmetry array, can implement AND-OR-INVERT functions, which are powerful enough to implement general computation. These arrays can be combined to create logic blocks capable of implementing sum-of-product functions, and still larger computations, such as state machines, can be obtained by adding additional routing blocks. We demonstrate the defect tolerance of such structures through experimental studies of the compilation of a small microprocessor onto a crossbar fabric with varying defect rates and compiler mapping parameters.

Distributed algorithms for maximum lifetime routing in wireless sensor networks

Abstract: A sensor network of nodes with wireless transceiver capabilities and limited energy is considered. We propose distributed algorithms to compute an optimal routing scheme that maximizes the time at which the first node in the network drains out of energy. The problem is formulated as a linear programming problem and subgradient algorithms are used to solve it in a distributed manner. The resulting algorithms have low computational complexity and are guaranteed to converge to an optimal routing scheme that maximizes the network lifetime. The algorithms are illustrated by an example in which an optimal flow is computed for a network of randomly distributed nodes.

Analysis of multipath Routing-Part I: the effect on the packet delivery ratio

Abstract: In this paper, we develop an analytical framework for evaluating multipath routing in mobile ad hoc networks. The instability of the topology (e.g., failure of links) in this type of network due to nodal mobility and changes in wireless propagation conditions makes transmission of time-sensitive information a challenging problem. To combat the inherent unreliability of these networks, we propose a routing scheme that uses multiple paths simultaneously by splitting the information between a multitude of paths, so as to increase the probability that the essential portion of the information is received at the destination without incurring excessive delay. Our scheme works by adding an overhead to each packet, which is calculated as a linear function of the original packet bits. The resulting packet (information and overhead) is fragmented into smaller blocks and distributed over the available paths. The probability of reconstructing the original information at the destination is derived in an analytical form and its behavior is studied for some special cases. It is shown that, under certain constraints, the packet dropping probability decreases as the number of used paths is increased.

On the effect of localization errors on geographic face routing in sensor networks

Abstract: In the absence of location errors, geographic routing - using a combination of greedy forwarding and face routing - has been shown to work correctly and efficiently. The effects of location errors on geographic routing have not been studied before. In this work we provide a detailed analysis of the effects of location errors on the correctness and performance of geographic routing in static sensor networks. First, we perform a micro-level behavioral analysis to identify the possible protocol error scenarios and their conditions and bounds. Then, we present results from an extensive simulation study of GPSR and GHT to quantify the performance degradation due to location errors. Our results show that even small location errors (of 10% of the radio range or less) can in fact lead to incorrect (non-recoverable) geographic routing with noticeable performance degradation. We then introduce a simple modification for face routing that eliminates probable errors and leads to near perfect performance.

Improvements on Ant Routing for Sensor Networks

Abstract: Ad-hoc wireless sensor networks have been an active research topic for the last several years. Sensor networks are distinguished from traditional networks by characteristics such as deeply embedded routers, highly dynamic networks, resource-constrained nodes, and unreliable and asymmetric links. Ant routing has shown good performance for communication networks; in this paper, we show why the existing ant-routing algorithms do not work well for sensor networks. Three new ant-routing algorithms are proposed and performance evaluations for these algorithms on a real application are conducted on a routing simulator for sensor networks.

Method for programming a routing layout design through one via layer

Abstract: A method for programming a routing layout design through one via layer includes forming a plurality of metal traces on a first routing layer and a second routing layer, and positioning a plurality of vias within a via layer disposed between the first and second routing layers for connecting the metal traces on the first and second routing layers according to a first current route defined by a predetermined circuit layout design to connect a first node and a second node so as to establish a second current route equivalent to the first current route.

Routing architecture exploration for regular fabrics

Abstract: In an effort to control the parameter variations and systematic yield problems that threaten the affordability of application-specific ICs, new forms of design regularity and structure have been proposed. For example, there has been speculation [6] that regular logic fabrics [1] based on regular geometry patterns [2] can offer tighter control of variations and greater control of systematic manufacturing failures. In this paper we describe a routing framework that accommodates arbitrary descriptions of regular and structured routing architectures. We further propose new regular routing architectures and explore the various performance vs. manufacturability trade-offs. Results demonstrate that a more regular, restricted routing architecture can provide a substantial advantage in terms of manufacturability and predictability while incurring a moderate performance penalty.

Blocking in all-optical networks

Abstract: We present an analytical technique of very low complexity, using the inclusion-exclusion principle of combinatorics, for the performance evaluation of all-optical, wavelength-division multiplexed networks with no wavelength conversion. The technique is a generalized reduced-load approximation scheme which is applicable to arbitrary topologies and traffic patterns. One of the main issues in computing blocking probabilities in all-optical networks is the significant link load correlation introduced by the wavelength continuity constraint. One of the models we propose takes this into account and gives good results even under conditions with high link load correlation. Through numerous experiments we show that our models can be used to obtain fast and accurate estimates of blocking probabilities in all-optical networks and scale well with the path length and capacity of the network. We also extend one of our models to take into account alternate routing, ina the form of Fixed Alternate Routing and Least Loaded Routing.

Traffic grooming, routing, and wavelength assignment in optical WDM mesh networks

Abstract: In this paper, we consider the traffic grooming, routing, and wavelength assignment (GRWA) problem for optical mesh networks. In most previous studies on optical mesh networks, traffic demands are usually assumed to be wavelength demands, in which case no traffic grooming is needed. In practice, optical networks are typically required to carry a large number of lower rate (sub-wavelength) traffic demands. Hence, the issue of traffic grooming becomes very important since it can significantly impact the overall network cost. In our study, we consider traffic grooming in combination with traffic routing and wavelength assignment. Our objective is to minimize the total number of transponders required in the network. We first formulate the GRWA problem as an integer linear programming (ILP) problem. Unfortunately, for large networks it is computationally infeasible to solve the ILP problem. Therefore, we propose a decomposition method that divides the GRWA problem into two smaller problems: the traffic grooming and routing problem and the wavelength assignment problem, which can then be solved much more efficiently. In general, the decomposition method only produces an approximate solution for the GRWA problem. However, we also provide some sufficient condition under which the decomposition method gives an optimal solution. Finally, some numerical results are provided to demonstrate the efficiency of our method.

DNA Display I. Sequence-Encoded Routing of DNA Populations

Abstract: Recently reported technologies for DNA-directed organic synthesis and for DNA computing rely on routing DNA populations through complex networks. The reduction of these ideas to practice has been limited by a lack of practical experimental tools. Here we describe a modular design for DNA routing genes, and routing machinery made from oligonucleotides and commercially available chromatography resins. The routing machinery partitions nanomole quantities of DNA into physically distinct subpools based on sequence. Partitioning steps can be iterated indefinitely, with worst-case yields of 85% per step. These techniques facilitate DNA-programmed chemical synthesis, and thus enable a materials biology that could revolutionize drug discovery.