Identification of anchor zones for floating content in VaNETs based on centrality measures

Abstract

Floating Content is the information with local and temporal validity and spatial relevance. These contents are produced and consumed by mobile nodes in a region called anchor zone. This floating content remains alive during its lifecyclewithout the need for fixed infrastructure, being maintained only by themobile nodes that consume and forward it—because of this, determining the most viable anchor zones to use floating content is one of the challenges of the Vehicular Network. This work presents the study and scientific experiment wherethe use of measures of centrality to identify the most viable anchor zones to spread the floating content proved to be effective. The study consisted of two parts: the first consisted of analyzing two real vehicular bases: one theMobile Century, which traffic of 2 900 vehicles on a section of 18km of "Nimitz Freeway", near Union City, California, in the United States, during February, 02 of 2008; other the T-Drive, which traffic of 8 388 vehicles from 02 to 08 of February of 2008 in a region of Beijing, China. In these two bases, two techniques were presented to identify the most viable anchor zones: GRID POSITION and BETWEENNESS CENTRALITY MEASURE. This study allowed us to observe the regions and times where there was the most significant flow of vehicles, through GRID POSITION technique and the regions where there was the most influential flow of vehicles using BETWEENNESS CENTRALITY. Due to not being able to verify which regions are more viable to use floating content, which motivated the second part of the work. The second part consisted in simulate two real bases over synthetic traffic: The first one shows the traffic of 18 000 vehicles in a section of 18km of "Nimitz Freeway" near Union City, California, in the United States. The second has the traffic of 100 000 vehicles in a region of Beijing, China. On these bases, we presented four model strategies, based on FLOW OF VEHICLES(State-of-The-Art), BETWEENNESS AND DEGREE CENTRALITY MEASURES and the HYBRID, mixed flow of vehicles and betweenness centrality to determine the anchor zones most viable in VANET scenarios. After identifying the most viable anchor zones in each strategy, we used a simulation where we verified in which of the strategies the floating content remained alive for longer and the number of vehicles affected. These simulation experiments showed that the strategies of centrality measures performed better than other strategies. The total simulation time was 18000s. By using centrality measures, the floating content remained alive for 17 008s on "Nimitz Freeway", USA and 13 579s in Beijing, China.