Equal-cost multi-path routing

About: Equal-cost multi-path routing is a research topic. Over the lifetime, 10472 publications have been published within this topic receiving 249362 citations.

Adaptive Position Update for Geographic Routing in Mobile Ad Hoc Networks

Abstract: In geographic routing, nodes need to maintain up-to-date positions of their immediate neighbors for making effective forwarding decisions. Periodic broadcasting of beacon packets that contain the geographic location coordinates of the nodes is a popular method used by most geographic routing protocols to maintain neighbor positions. We contend and demonstrate that periodic beaconing regardless of the node mobility and traffic patterns in the network is not attractive from both update cost and routing performance points of view. We propose the Adaptive Position Update (APU) strategy for geographic routing, which dynamically adjusts the frequency of position updates based on the mobility dynamics of the nodes and the forwarding patterns in the network. APU is based on two simple principles: 1) nodes whose movements are harder to predict update their positions more frequently (and vice versa), and (ii) nodes closer to forwarding paths update their positions more frequently (and vice versa). Our theoretical analysis, which is validated by NS2 simulations of a well-known geographic routing protocol, Greedy Perimeter Stateless Routing Protocol (GPSR), shows that APU can significantly reduce the update cost and improve the routing performance in terms of packet delivery ratio and average end-to-end delay in comparison with periodic beaconing and other recently proposed updating schemes. The benefits of APU are further confirmed by undertaking evaluations in realistic network scenarios, which account for localization error, realistic radio propagation, and sparse network.

Special issue on Rich Vehicle Routing Problems

Abstract: Editorial The Vehicle Routing Problem (VRP) is a key to efficient transportation management and supply-chain coordination. In broad terms, it deals with the optimal assignment of a set of transportation orders to a fleet of vehicles, and the sequencing of stops for each vehicle. The VRP has a large number of real-life applications and comes in many guises, depending on the type of operation, the time frame for decision making, the objective, and the types of constraint that must be adhered to. Outside of transportation logistics, the VRP has less intuitive but still important applications, e.g. in robotics and VLSI design. The VRP is a computationally hard, discrete optimization problem. It has been a main subject for thousands of researchers since it was introduced by Dantzig and Ramser in 1959. A large variety of optimization and approximation methods have been proposed and studied. Depending on variant and response requirements, exact VRP methods of today have a size limit of 50-100 orders. Hence, there has been much research on algorithms that are able to find high quality solutions in limited time. Our ability to find good solutions to practical variants of the VRP in a reasonable response time has increased tremendously since this problem was introduced. Improvements are not only due to a general increase in computing power, but also to substantial advances, both in exact methods and heuristics. VRP research is regarded as one of the great successes of Operations Research. The results have lead to a tool industry in route design and fleet management, through which research results have yielded huge economical and environmental savings. VRP research has often been criticized for being too focused on idealized models with non-realistic assumptions for practical applications. The methodological evolution has lead to a situation where the classical problems are now more or less regarded as being solved from a pragmatic point of view. As a result, the research community has turned to variants of the VRP which before were considered too difficult to handle. The variants include aspects of the VRP that are essential to the routing of vehicles in real-life. The family of those extended problems are often called Rich Vehicle Routing Problems. In addition to the internal motivation in the research community alluded to above, the growing tool industry and their end users provide external forces in the direction of richer VRP models. This is the backdrop for our …

Full-Chip Routing Considering Double-Via Insertion

Abstract: As the technology node advances into the nanometer era, via-open defects are one of the dominant failures due to the copper cladding process. To improve via yield and reliability, redundant-via insertion is a highly recommended technique proposed by foundries. Traditionally, double-via insertion is performed at the postlayout stage. The increasing design complexity, however, leaves very limited space for postlayout optimization. It is thus desirable to consider the double-via insertion at both the routing and postrouting stages. In this paper, we present a new full-chip gridless routing system considering double-via insertion for yield enhancement. To fully consider double vias, the router applies a novel two-pass, bottom-up routability-driven routing framework and features a new redundant-via aware detailed maze routing algorithm (which could be applied to both gridless and grid-based routing). We also propose a graph-matching based post-layout double-via insertion algorithm to achieve a higher insertion rate. In particular, the algorithm is optimal for grid-based routing with up to three routing layers and the stacked-via structure. Experiments show that our methods significantly improve the via count, number of dead vias, double-via insertion rates, and running times.