(4) Putting Nodes into Sleep Mode
- In DD, to save power, sensors are kept off until tasked by a reception of an
- Another example is the LEACH protocol which is based on a TDMA scheme.
Each member sends its data to the CH in its own time slot and it can go to the
sleep mode in other slots to conserve its energy.
(5) Load Balancing
- The LEACH protocol adapts dynamic clustering by dividing time into rounds
and, at the beginning of each round, the roles of CHs are rotated to balance the
energy consumption among the nodes.
- The GBR protocol deploys a traffic spreading technique to balance the traffic
load among the nodes. New data streams are not passed through nodes that are
currently part of the routes of other data streams.
- Another example is the Energy-Aware Routing protocol [ 41 ] which is a
variant of the DD protocol. Unlike DD which enforces one path to receive
data at higher rates, the Energy-Aware Routing protocol maintains multiple
paths at each node, and selecting the path is based on the energy consumption
level of each stored path. Having different paths selected at different times
balances the load and energy consumption among the nodes in the network.
- In the PEGASIS protocol, the role of chain leader is rotated among nodes in
the chain in a round robin fashion to balance the energy consumption among
(6) Use of Energy-Aware Metrics
- In addition to deploying dynamic clustering, the CH election process in
LEACH is based on the nodes' current residual energy.
- The GEAR protocol depends on the use of an energy-aware heuristic that
considers the geographical information as well for selecting the next-hop
toward the target region.
(7) Use of Restricted Flooding
- The GEAR protocol utilizes restricted flooding as one of the options for
disseminating packets within the area of interest.
With the scope of WSNs being expanded, researchers and application devel-
opers realized that, for some applications, there is a need for getting real-time and
precise information about the fast-changing events of the monitored phenomena.
This need for precise monitoring drove the need for designing sensor nodes
capable of capturing, storing, and sending multimedia data. Sensor networks
comprised of such powerful nodes are known as Wireless Multimedia Sensor
Networks (WMSNs). Generating and reporting multimedia data imposed some
stringent QoS requirements that should be met by WMSNs and their protocols,
including the routing protocols. WMSNs routing protocols should add to the tra-
ditional WSN protocols some techniques for handling the QoS requirements such