Routing Techniques in Wireless Sensor Networks: A Survey - Part2

Directed Diffusion: It is a data-centric application paradigm where Base Station (BS) broadcasts the interests and sources will reply to the interests. Even though this protocol is very popular it has its own drawbacks. This is unsuitable for one-time queries, is not applicable to applications that require continuous data delivery to the BS and is not energy efficient.

Rumor Routing: This protocol floods the events rather than queries and each node maintains an event table and generated agent which propagate information to distant nodes. This protocol is energy-efficient and handles node-failures but doesn't work well when number of events is large.

MCFA: This algorithm exploits the fact that the direction of routing is always known and nodes doesn't have to maintain a routing table. In this each message is broadcasted to its neighbors and node checks if it is on the least-cost path between the sensor node and the base station.

Gradient-Based Routing (GBR): Key idea of this protocol is to memorize the height of the node (min number of hops) to the base station when interest is diffused. GBR uses data aggregation and traffic spreading to uniformly divide the traffic over the network. Three different data dissemination techniques are discussed in GBR, Stochastic scheme, Energy-based scheme and Stream-based scheme.

COUGAR: This protocol adds a query layer that lies between the network and application layers. Sensor nodes select a leader node to transmit the data. Base Station generates a query plan which specifies the flow of data and selection of leader to a query. In this protocol, addition of query layer to each node is an overhead and leader nodes should be dynamically maintained to prevent them from being hot-spots.

ACQUIRE: This protocol divides complex queries into sub-queries. When BS sends query each node tries to respond to query before forwarding it to another node. This protocol is not evaluated through simulations.

Energy-Aware Routing: The main objective of this protocol is to increase network lifetime. In this set of paths are maintained based on energy-levels. Route set up is complicated in this protocol.

LEACH : In this few nodes act as cluster head nodes and these nodes are rotated. This protocol is operated in two-phase. In setup phase clusters are organized and cluster heads are selected. In steady phase data is transferred to base station. Some issues with LEACH are, assumes all nodes can transmit with enough power and also assumes that cluster heads consume same energy as non-cluster head nodes.