Abstract
Self-organization is a phenomenon in nature which has been studied in several areas, namely biology, thermodynamics, cybernetics, computing modeling, and economics. Systems exhibiting self-organization have well defined characteristics such as robustness, adaptability, and scalability, which make self-organization an attractive field of study for two kinds of applications: a) maintaining the communication among mobile devices in wireless networks, and b) coordination of swarms of mobile robots. In ad hoc networks, there is not necessarily an underlying infrastructure in which the nodes can maintain communicated with other nodes; so due to this feature, it is necessary to provide efficient self-organization algorithms for routing, managing, and reconfiguring the network. Furthermore, self-organization in nature provide clear examples about how complex behaviors can arise from only local interaction between entities, namely the ants colony, feather formation, and flock of birds. Based on the above mentioned examples, several algorithms have been proposed to accomplish robot formations using only local interactions. Due to resource constraints in mobile devices, selforganization requires simple algorithms for maintaining and adapting wireless networks. The use of resources for establishing robot formations can be reduced by improving simple rules to accomplish the formation. This article first presents a brief overview of several works developed in ad hoc networks; then, delves deeper into the key algorithms; and finally, challenges arising in this area are discussed.
TopBackground
Self-organizing networks can be classified as follows:
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Mobile Ad hoc Networks (MANET). In this kind of network the nodes are mobile devices operating under energy consumption constraints.
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Wireless Mesh Networks (WMNs). The backbone of the network consists of mesh routers (which have reduced mobility) allowing the communications between mobile mesh clients. (Figure 1).
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Wireless Sensor Networks (WSNs). They are composed of a large number of sensor nodes widespread on a field; they are used for collecting information on the environment and transmitting such information to themselves or to a base station (Figure 2).
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Vehicular Ad Hoc Networks (VANETs). These networks use ad hoc communications for detecting obstacles on the road and emergency events by exchanging information obtained from the roadside or from other vehicles (Figure 3).
A common feature of these networks is the mobility of nodes; furthermore, there exists not always a relaying structure. These facts evidence the need for including within the network management systems, strategies for maintaining communication between nodes despite the mobility.
In next section, several approaches for solving this problem are presented. Although there are some issues not addressed yet, this overview may be aware to the reader about the state of art in this area.
TopSelf-Organization In Ad-Hoc Networks
An ad-hoc network may be structured in three ways: flat topology, hierarchical topology, and hybrid topology (Dressler, 2006; Tang & Tienfield, 2006). Hierarchical topology is the most widely used because it is scalable, allowing for efficient routing protocols for large networks; furthermore, it has well stated battery consumption schemas. The hybrid topology is suitable for combining ad hoc networks with existing network infrastructures.
Key Terms in this Chapter
QoS (quality of service): Set of technologies that provide a reliable data transmission ensuring data quality.
Wireless Networks: Networks that do not need wires to allow the communication; instead they use wireless technologies as 802.11, WiFi, WiMax, Zigbi, and so forth.
Cluster-Based Algorithms: These kinds of algorithms organize the nodes in clusters where a clusterhead is elected. The members of the cluster can communicate with nodes in other clusters through clusterhead.
Bio-Inspired Algorithms: Algorithms based on living beings’ behaviors to accomplish a task efficiently.
Mobile Devices: Computer-based communication devices that give us the possibility to be connected wherever we are at any time.
Self-Organization: Phenomenon in nature which allows the spontaneous appearing and maintaining of a functional structure ( Tang & Tienfield, 2006 ).
Ad-hoc Networks: Networks that do not need an infrastructure to allow the communication. The communication is established between devices using a wireless technology.