Localized and emergent protocols: Localized protocols
A localized protocol for a sensor network is a protocol in which all information processed by a node is either: (a) local in nature (i.e. they are properties of the node’s neighbors or itself); (b) global in nature (i.e. they are properties of the sensor network as a whole), but obtainable immediately (in short constant time) by querying only the node’s neighbors
or itself. Localized protocols have the following benefits:
ŘScalability. Localized protocols allow nodes to act independently and simultaneously in various parts of the network. Hence, localized protocols often exhibit better scalability in large networks than centrally controlled protocols, which may have to wait for information to propagate across the network.
ŘRobustness. When information use is purely local and no centralized control infrastructure is needed, the chances for protocol failure due to transmission errors and node failure are reduced.
The definition of an emergent algorithm is outlined by Fisher and Lipson. An emergent protocol for sensor network is localized protocol in which the desired global property is explicitly neither encoded in the protocol nor organized by a central authority, but emerges as a result of repeated local interaction and feedback between the nodes. One of the main distinguishing characteristics of emergent protocols over other localized protocols is the existence of feedback during protocol operation. Feedback occurs when some node A affects some node B, which then directly or indirectly affects node A again. Due to the reliance on repeated feedback, emergent protocols are commonly iterative in nature, requiring several rounds of communication between a node and its neighbors.