In this chapter, the idea of formulating the node connectivity into a form suitable for the purpose of monitoring the dynamic of any given node pair was proposed. It had been able to show that the node connectivity time constitutes the length of time where node-pairs are connected and communication sessions can be established. By analytical calculation and simulation, the node connectivity time depends on the relative velocity of the node-pair. It shows that there is an upper limit and a lower limit for the connection time. Between these limits, communication sessions can be carried out. In order to monitor the quality of connection between a node-pair and for the whole route which is made up of a collection of node-pairs, npem, npcm, and nci are introduced. The nci is shown to be a viable way to estimate the quality of node-pair connection in terms of its timeliness. The index, nci, could be used as one of the metrics to identify and select the best path to the destination.
TopIntroduction
Mobile ad hoc network (MANET) is formed by a group of nodes that communicate with each other over a single or multiple wireless channels. They operated in a decentralized and self–organizing manner without the necessity for a fixed wireless networking infrastructure. An outstanding feature of MANET is the multihop mode of communications, beyond the direct radio connection amongst the nodes. Each node could be a transmitter, a receiver or a router forwarding data traffic toward its destination. The fundamental idea of such networks goes back to the 1980s (I. Chlamtac, M. Conti, and J. J.-N. Liu (2003)), but have shown an increase in research interest recently, due to emerging technology in wireless communications and the microelectronic industries. A node is typically equipped with a radio transmitter and receiver, which allows communication sessions with other nodes. Salient features of MANET are; (1) its implementation could increase the mobility and flexibility, as it can be activated in a very short time; (2) it can be more economical due to limited infrastructure costs; (3) more robust than conventional wireless networks because of their non-hierarchical distributed control mechanisms; (4) due to its multi-hop character, communication could be established beyond the Line of Sight (LOS); (5) low power consumption of wireless devices, attributed to less power is required for sending a signal over any distance in multiple shorter hops. Several application scenarios, such as mobile computers for conferencing and home networking, wireless sensor networks (I.F. Akyildiz, W. Su, Y. Sankara subramaniam and E. Cayirci (2002)), multihop extensions of cellular telecommunication systems (X. Jiang et al (2004)), and vehicular networking (K. J. Wong et al.(2003), C. Lochert et al.(2003)) are the favourites amongst the researchers today. This technology has been proposed as a complementary to the fourth-generation wireless networks. Nodes typically rely on each other to establish communication sessions. Hence, network connectivity could be regarded as a fundamental characteristic for the proper functionality of the network. The node density, number of nodes, transmission range and the spatial nodes distribution generally affect node connectivity.
Nodes in MANET are typically mobile with some mobility characteristics. The dynamicity of MANET topology is due to nodes mobility. Mobile nodes also perform as router to the packet transmission, hence each single node contributes to the node and network connectivity. The connectivity failed, if a node inadvertently fails and secondly when the spatial density of the nodes is too low. Connectivity is one of the most fundamental aspects of MANET. Network connectivity of MANET is a complex problem due to the uncertainty of the network topology. A number of studies concerning network connectivity modeling and analysis of a particular MANET have been reported in the recent technical literature (P. Santi and D. M. Blough (2002), P. Santi (2005), C. Bettstetter (2002), O. Dousse, P. Thiran, and M. Hasler (2002), M. Desai and D. Manjunath (2002), C. H. Foh and B. S. Lee (2004)). All these research works aim at providing a mean to calculate the Quality of Services (QoS) measured in terms of the probability of network connectivity.