Many protocols depend on the source-initiated techniques and these protocols
are typically designed for applications like the data gathering or object tracking
applications. Some of these protocols send their actual data to the data collector
without any prior negotiation and others deploy, preceding the actual data trans-
mission, a kind of meta-data advertisement for conserving the energy that may be
wasted in sending and receiving data that is not of interest to others. What follows
are examples of protocols that utilize source-initiated techniques:
• Actual Data Transmission Based
- The Low Energy Adaptive Clustering Hierarchy (LEACH) protocol [ 29 ]is
the first and most popular energy-efficient hierarchical clustering algorithm
for WSNs. Nodes in LEACH are partitioned into clusters with each cluster
member reporting data periodically to its cluster-head (CH). Each CH collects
the data from its cluster members, then aggregates and sends it directly to the
BS. The election of CHs is a distributed, stochastic, energy-aware process that
is run locally at the nodes. Heinzelman et al. also presented a variant, called
LEACH-Centralized (LEACH-C), which moves the burden of the CH elec-
tion to the BS.
- The Minimum Cost Forwarding Algorithm (MCFA) [ 30 ] exploits the fact that
the destination is always known; it is the BS. In MCFA, each node maintains
the least cost path estimate from itself to the sink. The source broadcasts the
data to its neighbors. A node receiving a packet will rebroadcast it if the node
is on the least cost path between the source and the sink.
- The Power-Efficient Gathering in Sensor Information Systems (PEGASIS)
protocol [ 31 ] is a hierarchical chain-based protocol. The chain in PEGASIS is
the set of nodes that are closest to one another and form a path to the BS. Each
node sends its data only to its next node in the chain, the nearest one to it.
Each chain has a chain leader that collects the data from other nodes in the
chain, then aggregates and sends it directly to the BS.
- To improve the performance of the traditional hierarchical protocols such as
LEACH and PEGASIS, a trend of engaging artificial intelligence techniques
in establishing a route and forming the network hierarchy is being adopted.
Some examples of these intelligent hierarchical protocols that involve actual
data transmissions are the protocols proposed in [ 32 , 33 ]. In Ref. [ 32 ], Kumar
et al. proposed a routing protocol based on a genetic algorithm (GA) that
handles the clustering and network configurations as an optimization problem.
The goal of their proposed protocol and use of a GA is to minimize the
number of cluster-heads for less channel contention and higher efficiency. The
protocol divides the network into a number of independent clusters using a
GA that determines the number of clusters, cluster-heads, members of each
cluster, and the transmission schedules for a given number of transmissions.
Simple heuristics are used to keep energy efficient clusters for a longer time
than less energy efficient clusters. The clustering setup and configurations are