Query-Points Visibility Constraint Minimum Link Paths in Simple Polygons

We study the query version of constrained minimum link paths between two points inside a simple polygon P with n vertices such that there is at least one point on the path, visible from a query point. The method is based on partitioning P into a number of faces of equal link distance from a point, called a link-based shortest path map (SPM). Initially, we solve this problem for two given points s, t and a query point q. Then, the proposed solution is extended to a general case for three arbitrary query points s, t and q. In the former, we propose an algorithm with O(n) preprocessing time. Extending this approach for the latter case, we develop an algorithm with O(n3) preprocessing time. The link distance of a q-visible path between s, t as well as the path are provided in time O(log n) and O(m + log n), respectively, for the above two cases, where m is the number of links.

Analysis of Delay-Tolerant Routing Protocols using the Impact of Mobility Models

Intermittently connected mobile networks are sparsely connected wireless ad-hoc networks where there is no end-to-end path from a source device to a destination. Generally, these paths do not exist. Hence, these devices use intermittent path using the concept of the store-and-forward mechanism to successfully do the communication. These networks are featured by long delay, dissimilar data rates, and larger error rates. Hence, we see the analysis of several delay-tolerant routing protocols, e.g., epidemic, spray-and-wait, prophet, maxprop, rapid, and spray-and-focus using opportunistic network environment simulator. At first, the investigations of the above considered routing protocols are done across three mobility models namely random direction, random walk, and shortest path map based movement mobility model for node impact only. Then, we evaluate these routing protocols against the impact of message copy, buffer, and time-to-live using shortest path map considering the result of node impact. We use three metrics and the result shows that spray-and-focus deserves good performance for showing higher delivery, lower latency, and lower overhead among all routing techniques while epidemic the poor.

Bonding Based Technique for message forwarding in Social Opportunistic Network

Integrating social networks properties such as centrality, tie strength, etc into message forwarding protocols in opportunistic networks has grown into a vital major benchmark. The opportunistic network is a demanding network with no set route to travel a message from the source to be able to the destination. During these networks, nodes use possibilities gained based on store-carry-forward patterns to forward communications. Every node that obtains a message when it activities another node makes selection concerning the forwarding or not necessarily delivering the node came across. Most of these message forwarding protocols use the benefit of social properties information like contact information and social relationship enclosed by the nodes in the social opportunistic network. In this paper, a Bonding based forwarding technique is proposed which is finding direct and indirect bonding among nodes by exploiting contact information and social pattern. In the proposed protocol, we also focus on indirect bonding by finding weakest direct bonded nodes and then replace it with strong indirect bonded nodes of the network. In this work, the balance between transmission delay and network traffic is considered by using shortest path map based mobility model. ONE simulator is used for simulation and performance of the proposed protocol is compared contrary popular approaches for instance Epidemic, PRoPHET, and BubbleRap, and Interaction based when using the shortest path map based mobility model. The Bonding based forwarding technique performs adequately well concerning the number of messages delivered, overhead ratio, message dropping and average latency.

OPTIMAL CONSTRUCTION OF THE CITY VORONOI DIAGRAM

We address proximity problems in the presence of roads on the L1 plane. More specifically, we present the first optimal algorithm for constructing the city Voronoi diagram. We apply the continuous Dijkstra method to obtain an optimal algorithm for building a shortest path map for a given source, and then it extends to that for the city Voronoi diagram. Moreover, our algorithm can be extended to other generalized situations including metric spaces induced by roads and obstacles together.

SHORTEST PATHS AMONG OBSTACLES IN THE PLANE

We give a subquadratic (O(n3/2+∊) time and O(n) space) algorithm for computing Euclidean shortest paths in the plane in the presence of polygonal obstacles; previous time bounds were at least quadratic in n, in the worst case. The method avoids use of visibility graphs, relying instead on the continuous Dijkstra paradigm. The output is a shortest path map (of size O(n)) with respect to a given source point, which allows shortest path length queries to be answered in time O( log n). The algorithm extends to the case of multiple source points, yielding a method to compute a Voronoi diagram with respect to the shortest path metric.