An experimental evaluation and guideline for path finding in weighted dynamic network

Shortest path computation is a building block of various network applications. Since real-life networks evolve as time passes, the Dynamic Shortest Path (DSP) problem has drawn lots of attention in recent years. However, as DSP has many factors related to network topology, update patterns, and query characteristics, existing works only test their algorithms on limited situations without sufficient comparisons with other approaches. Thus, it is still hard to choose the most suitable method in practice. To this end, we first identify the determinant dimensions and constraint dimensions of the DSP problem and create a complete problem space to cover all possible situations. Then we evaluate the state-of-the-art DSP methods under the same implementation standard and test them systematically under a set of synthetic dynamic networks. Furthermore, we propose the concept of dynamic degree to classify the dynamic environments and use throughput to evaluate their performance. These results can serve as a guideline to find the best solution for each situation during system implementation and also identify research opportunities. Finally, we validate our findings on real-life dynamic networks.

Analysis of Bird Flyways in 3D

Bird migration is a long studied phenomenon that involves animals moving back and forth from wintering sites and to reproductive grounds. Several studies have focused on identifying the timing, physiology and evolution of migration, but a spatial approach to understand the migratory routes is still an open challenge. Geographic Information Systems (GIS) can provide the tools to explore such a complicated issue. Birds usually move from the wintering sites to spring breeding grounds in multiple flights, stopping at intermediate sites to rest and refuel, being unable to cover the distance in a single travel. The choice of stopover sites by birds depends not only on their ecological features but also on their position and visibility along main migratory flyways. In this work, we calculated the possible migratory routes that minimize the distance covered or the elevation gaps for birds crossing the Southern Alps, simulating the flight within a network connecting potential stopover sites and other relevant point of passage, using the shortest path computation. Subsequently, we performed a visibility analysis along the identified flyways to understand which stopover sites, belonging to the Natura2000 network, were visible for a bird in an area with complex morphology. Data available from ringing stations confirm the selection or avoidance of some stopover sites based on their en route visibility. The knowledge of bird flyways and stopover sites has implications for conservation as well as for planning, especially for wind farms or other infrastructures.

Um Novo Algoritmo IA-RSA Ciente de Imperfeições de Camada Física para Redes Ópticas Elásticas

Este artigo prop õe um novo algoritmo de roteamento e alocação de espectro ciente dos efeitos de camada física (IA-RSA - Impairment-Aware Routing and Spectrum Assignment) para redes ópticas elásticas. O objetivo do algoritmo proposto é reduzir a probabilidade de bloqueio causada pela degradação da qualidade de transmiss ão quando novos circuitos s ão estabelecidos. O algoritmo proposto é comparado com outros algoritmos IA-RSA: Modified Dijkstra Path Computation (MD-PC) e K-Shortest Path Computation (KS-PC). Resultados de simulação mostram que o algoritmo proposto apresenta um desempenho superior ao dos algoritmos MD-PC e KS-PC em termos de i) probabilidade de bloqueio de circuitos, ii) probabilidade de bloqueio de banda, iii) justiça no atendimento de diferentes pares de n ós origem e destino e iv) justiça no atendimento de diferentes larguras de banda para as topologias EON e NSFNet.