Coloured Petrinet for Modelling and Validation of Dynamic Transmission Range Adjustment Protocol for Ad Hoc Network

Abstract

The IEEE 802.11 standard defines two operational modes for WLANs: infrastructure based and infrastructureless or ad hoc. A wireless ad hoc network comprises of nodes that communicate with each other without the help of any centralized control. Ad hoc implies that the network does not rely on a pre-existing infrastructure but rather each node participates in routing by forwarding data for other nodes. The decentralized nature improves the scalability of wireless ad hoc network as compared to wireless managed networks.
Each node acts as either a host or router. A node that is within the transmission range of any other node can establish a link with the later and becomes its immediate neighbour.
However, the nodes in the ad hoc networks are constrained with limited resources and computation capability. So it may not be possible for a node to serve more number of neighbours at some instant of time. This enforces a node to remain connected or disconnected with few of its existing neighbours supporting the dynamic restructuring of the network. The presence of dynamic and adaptive routing protocol enables ad hoc networks to be formed quickly.
The Dynamic Transmission Range Adjustment Protocol (DTRAP) provides a mechanism for adjusting transmission range of the ad hoc nodes. They maintain a threshold number of registered neighbours based on their available resources. The node protects its neighbourhood relationship during data communication by controlling its transmission range.
It registers or de-registers a communicating node as its neighbour by dynamically varying the transmission range. However a node has a maximum limit on its transmission range.
If the distance between the node and its neighbour is less than the transmission range and;
1)if the number of neighbours of a node falls short of threshold value, the node dynamically increases its transmission range in steps until it is ensured of an optimal number of neighbours
2)if the number of neighbours of a node exceeds the threshold value, the node dynamically decreases its transmission range in steps until it is ensured of an optimal number of neighbours.
Coloured Petri nets (CP-nets) is the modelling language tool used for systems having communication, synchronisation and resource sharing as significant aspects. It provides
a framework for the design, specication, validation, and verication of systems. It describes the states in which the system may be in and the transition between these states.
The CPN combines Petri nets and programming languages. Petri nets amalgamate the use of graphical notation and the semantical foundation for modelling in systems. The functional programming language standard ML provides the primitives for the definition of data types and manipulation of data values. Besides providing the strength of a graphical modelling language, CP-nets are theoretically well-founded and versatile enough to be used in practice for systems of the size and complexity of industrial projects.