and inefficient bandwidth utilization. On the other hand, this redundancy of data
can be advantageous. By utilizing data aggregation techniques, this redundancy
can be exploited by the routing protocol to decrease the number of transmissions
and hence, improve the energy efficiency and the bandwidth utilization.
(i) Diverse Applications
WSNs have a wide range of applications each with its own requirements.
Therefore, there is no ''one-for-all'' protocol; the requirements of the data gath-
ering applications are different from those that focus on critical event reporting.
The protocol designers should develop the protocol in a way that satisfies the needs
of the application and utilizes the resources efficiently.
Having all these unique challenges for WSNs has forced the design of new
routing protocols instead of using the existing protocols of MANETs. New pro-
tocols have been needed to meet all these design challenges and provide the
needed network performance. To make the WSN operational for several years, the
energy efficiency should be the primary design goal in any WSN protocol.
Wireless Mesh Networks
Routing for WMNs plays a crucial role for providing WMN services with the
required quality for users. WMNs have some unique characteristics that impose
distinguishing challenges, and features that offer opportunities for improvement
when designing a WMN routing protocol. The most prominent ones are:
(a) QoS Guarantee
As the main objective of a WMN is providing broadband services, routing for
WMNs should depend on the use of QoS and link quality metrics to satisfy the
QoS requirements; minimize delay, provide real time communications, and bal-
ance the load between the multiple available paths.
(b) Robust Coverage
To guarantee QoS and provide efficient services, the WMN should be more
robust to network faults and link failures. Dead zones can be eliminated by adding
mesh routers and by the proper placement of routers to avoid service disruptions.
A WMN routing protocol should utilize the availability of multiple paths between
the potential source-destination pairs. Such redundancy of communication paths
can also impose challenges for the routing protocol due to increased complexity
for maintaining these paths.
(c) Minimal Mobility
In the backbone WMN, WMRs are almost stationary. With such static
deployment, mobility support in WMNs is not a major concern. This releases the