Image Processing Reference
In-Depth Information
7.2.3 Cluster-Based Routing Protocols
Another critical aspect for energy consumption is the presence of nodes which, being either closer
to the sink or on the optimal (e.g., minimum cost) path to the sink, perform more relaying than
the other nodes, thus depleting their energy reserve faster than the others. When such nodes run
out of energy, network survivability is compromised, and when all the nodes closest to the sink die,
the sink itself becomes unreachable. To avoid this problem, hierarchical or cluster-based routing was
introduced. In cluster-based routing, special nodes called cluster heads form a wireless backbone to
the sink. Each of them collects data from the sensors belonging to its cluster and forwards it to the
sink. In heterogeneous networks, cluster heads may be different from simple sensor nodes, being
equipped with more powerful energy reserves. In homogeneous networks, on the other hand, in
order to avoid a quick depletion of cluster heads, the cluster head role rotates, i.e., each node works
as a cluster head for a limited period of time. Energy saving in these approaches can be obtained
in many ways, including cluster formation, cluster-head election, etc. Some of these approaches also
perform data aggregation at the cluster-head nodes to reduce data redundancy and thus save energy.
Notable examples of cluster-based routing protocols are LEACH [Hei] and its extensions, which
will be discussed in Section ..
7.2.4 Location-Based Routing Protocols
Location-based routing protocols use position information for data relaying. Location information
can be exploited for energy-efficient data routing in WSNs as, based on both the location of sensors
and on knowledge of the sensed area, a data query can be sent only to a particular region of the
WSN rather than the whole network. his feature of location-based routing protocols may allow for
a significant reduction in the number of transmissions and thus in the power consumption of sensor
nodes. Location-based routing protocols will be discussed in Section ..
7.2.5 QoS-Enabled Routing Protocols
A number of routing algorithms for WSNs which take some kind of QoS into account have been
proposed. QoS is usually addressed in terms of either end-to-end or average delay, or deadline miss
ratio. Some of these protocols are energy-aware, while others are not. A notable non-energy-aware
QoS-enabled protocol is SPEED [He] [He], a well-known protocol which combines feedback
control and nondeterministic geographic forwarding to achieve a predictable end-to-end commu-
nication delay under given distance constraints. The basic idea of SPEED is to maintain a desired
delivery speed across the sensor network. Although SPEED is not energy-aware, it inspired a number
of energy-aware QoS-enabled routing protocols for WSNs, some of which will be described in
Section ..
7.3 Data-Centric Power-Efficient Routing Protocols
7.3.1 Sensor Protocols for Information via Negotiation
The aim of the family of adaptive negotiation-based protocols for WSNs called SPIN, presented
in [Kul], is to efficiently disseminate information among sensors in an energy-constrained environ-
ment. he basic idea in SPIN is to name the data using high-level descriptors called metadata. he use
of metadata negotiation reduces the transmission of redundant data throughout the network, as com-
pared to the classic Flooding protocol. Hence, SPIN protocols address major problems of flooding,
i.e., message implosion, overlap, and resource blindness (as SPIN protocols are energy-aware).
This is done by negotiating data at the sensor nodes before transmission occurs and introducing
