On search sets of expanding ring search in wireless networks

We focus on the problem of finding the best search set for expanding ring search (ERS) in wireless networks. ERS is widely used to locate randomly selected destinations or information in wireless networks such as wireless sensor networks In ERS, controlled flooding is employed to search for the destinations in a region limited by a time-to-live (TTL) before the searched region is expanded. The performance of such ERS schemes depends largely on the search set, the set of TTL values that are used sequentially to search for one destination. Using a cost function of searched area size, we identify, through analysis and numerical calculations, the optimum search set for the scenarios where the source is at the center of a circular region and the destination is randomly chosen within the entire network. When the location of the source node and the destination node are both randomly distributed, we provide an almost-optimal search set. This search set guarantees the search cost to be at most 1% higher than the minimum search cost, when the network radius is relatively large

Linear search problem with low sensing on two rays

We consider a generalization of the linear search problem where the searcher has low sensing capabilities on two rays. We first show the necessary conditions for an optimal search plan to exist. We then investigate properties of optimal search plans and show that optimal search plans are defined by an underlying fourth order recurrence relation. We then develop numerical methods that aid in estimating and finding optimal search plans. In Chapter 4, we present an algorithm that produces a search plan that approximates the minimum expected cost up to any desired accuracy for any probability density distribution. In Chapter 5, for specific distributions, properties of the underlying dynamics are used to numerically find optimal search plans

Dienstbasierte Kommunikation über unzuverlässige drahtlose Verbindungen für selbstorganisierende Sensor-Aktor-Netze

Die in dieser Arbeit vorgestellte ServiceCast-Architektur umfasst Lösungen zur dienstbasierten Adressierung und Kommuikation in drahtlosen Sensor-Aktor-Netzen. Besondere Beachtung kommt der realistischen Repräsentation und Kalibrierung des indeterministischen drahtlosen Kanals in Simulationen und dessen Auswirkungen auf Mechanismen höherer Protokolle zu. Diesen besonderen Randbedingungen wird durch neue Formen der Adressierung und Zustellung von Daten (z.B. Somecast) Rechnung getragen

Flood Search under the California Split Rule

We consider flood search on a line and show that no algorithm can achieve an average-case competitive ratio of less than 4 when compared to the optimal o#-line algorithm. We also demonstrate that the optimal scanning sequences are described by simple recursive relationships that yield surprisingly complex behavior related to Hamiltonian chaos