Replica Distribution Scheme for Location-Dependent Data in Vehicular Ad Hoc Networks using a Small Number of Fixed Nodes

In vehicular ad hoc networks (VANETs), it is difficult for nodes to reliably access data on other nodes due to the mobility of vehicles. To improve the accessibility by certain vehicles to data generated at other vehicles, it is effective to distribute replicas of such data. However, if the density of vehicles is low, it is difficult to distribute an adequate number of replicas. In this paper, we propose the System for Sharing Objects with Location information on Ad hoc Network Fixed Node eXtention (SOLA-FX). SOLA-FX utilizes a small number of fixed nodes that are not connected to the infrastructure network. They are placed at intersections to support the storage and distribution of location-dependent data generated by vehicles, and forwarding of request/reply messages. We conducted simulations to determine suitable positions of the fixed nodes and an effective replica distribution operation between vehicles and the fixed nodes. The results showed that arranging fixed nodes in an area where location-dependent data items are frequently generated improves the accessibility to replicas with a small number of fixed nodes. We also confirmed that making each fixed node broadcast a replica when it has been received by a few vehicles in a previous replica distribution improves the accessibility to the replica with low replica distribution overhead.