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An Introduction to a GIS-Based In-Road Information Network
Karim Mohammadi
Iran University of Science and Technology
mohammadi@iust.ac.ir
S. Shahab Sahhafi
Iran University of Science and Technology
sssahhafi@ee.iust.ac.ir
Abstract—
This paper proposes a new in-road information network to significantly improve Location Service and Routing Protocol based on GIS (Geographic Information System) road map, speed and location of vehicles. Recent surveys have shown that current in-road information networks are inefficient to find a destination node in long-distant routes (Location Service), and unable to transfer information between source and destination easily for high-speed vehicles (Routing Protocol). In order to overcome these difficulties the new in-road information network suggests using communication map layer and considering each vehicle speed and location, to divide in-road network into two hierarchical levels and makes it similar to a chain of cells. As a matter of fact, these are the cells which virtually communicate with each other, and make Location Service and Routing Protocol become easy and possible. The paper just observes the network layer, and physical layers and interfaces are ignored.
I. INTRODUCTION
This paper presents a new method based on Geographical Information system (GIS) maps in making an efficient location service and routing protocols for in-road information networks. Creating an in-road information network as an infrastructure for the inter-vehicle communication has been considered recently. The main goal of this network is to transfer traffic data and improve the safety of the road transportation. However, there are some problems which may reduce the reliability and affect the performance of an in-road information network: it is difficult to find a specific vehicle (node) in this large network. On the other hand, it is difficult to track a destination vehicle in the network and forward a data packet to it, even when the current position of the destination node is known.
Mobile ad hoc networks which are made by distributed mechanisms and cooperation among all the nodes are bases of in-road information networks [1] [2].
Problems with physical layer, in which high speed vehicles decrease the capability of current spread spectrum standards, and network layer, in which location service and routing protocol are not reliable, affect the in-road performance of mobile ad hoc networks.
Roads characteristics with fast and unpredictable movements of vehicles drastically increase rate of the change in an in-road information network topology, so location services and routing algorithms in current ad hoc networks have many limitations in road communication. This is because relative positions of vehicles are frequently changed and make creating, control and maintenance of routes very difficult. Also, it makes an increase in the amounts of control messages and beacons which are using network band width improperly.
Overcoming this problem, vehicle position data is needed. So that, each vehicle should be equipped with a GPS receiver to get its own instant geographical coordination. On the other hand, in a position-based network a source needs to know a destination position before sending data, so it must flood a request message in all directions of the network. Although this mechanism can determine the destination position, it is a consuming time and high-cost procedure. However, by using maps, storing and processing spatial and non-spatial data in Geographical Information System (GIS), time and cost will be saved.
The objective of this paper is to develop a new method to design network hierarchy structure based on GIS information and roads maps.
It is hypothesized that all of network nodes (vehicles) are equipped with GPS receivers, maps, GIS and required communication equipment inside.
II. GIS-BASED NETWORK ZONES
Position is an important data in networks using position–based routings. Large networks use hybrid routing protocols []. So, the whole network should be divided into many zones with unique IDs (Zone ID). In fact, Zone IDs are very important because they are a part of the address field of each packet. Furthermore, each node has a unique ID, too. Making a packet address, a node has to integrate its ID and its relative zone ID.
In many mobile ad-hoc networks, zones depend on node existence. It means that, some nodes together make a zone, so if these nodes separate from each other, that zone may be divided into smaller zones. Also, it is possible a zone to be eliminated or merged with other ones.
According to importance of packet address field, it must be guaranteed that there aren’t any similar IDs for different zones. This makes sure that the sending data packet can be received properly in the destination. To achieve this aim, making vehicle-independent zones for in-road information network is proposed. Nowadays, some cars have GIS maps in their navigation systems. It is expected that in future, most of the cars will have this system with them, so they can identify in which road they are moving along.
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