Networking Reference
In-Depth Information
as achieving low delay, high throughput, and a satisfactory level of reliability
while keeping the main goal of improving energy efficiency. For the data for-
warding techniques to be adopted by WMSNs, only the event-based and query-
based techniques are considered. The continuous reporting model is not suitable
for use in such networks because the continuous delivery and compression of
multimedia data is very energy-consuming which will lead to a fast depletion of a
node's battery. With these special routing requirements, there is an interest in
developing WMSN routing protocols that consider QoS and handle the multimedia
reporting challenges. Some of these protocols can be found in [ 42 , 43 ]. Although
QoS is considered in those protocols, it is still considered an auxiliary requirement
for the traditional WSNs.
Wireless Mesh Networks
WMNs are comprised of almost stationary nodes. This feature leads to relaxing the
mobility and energy constraints. Therefore, WMNs are not in need of auxiliary
routing components. The WMN core components are the three main core routing
components: route discovery, route selection, and route representation and data
forwarding. The WMN QoS requirements and needs can be handled by special
metrics and functionalities involved in the route selection component as will be
discussed later in this section.
(a) Route Discovery
Some protocols, for route discovery, are proactive, others are reactive, and
some are based on hybrid techniques.
(1) Proactive-based
- The Light Client Management routing Protocol (LCMP) [ 44 ] makes use of
two routing tables for maintaining the topology information; a table for
maintaining information about the local mesh clients and another table for
recording information about the remote clients and the mesh routers associ-
ated to them.
- The Tree-Based Routing (TBR) Protocol [ 45 ] is the proactive part of the
default, hybrid routing protocol proposed by IEEE 802.11s for WMNs. TBR
depends on broadcasting beacon messages carrying the gateway's information
to maintain a tree-like topology. TBR assumes that all traffic is either directed
to/from the gateway and it maintains a multi-hop path from each mesh router
to the tree root, the gateway. The drawback of TBR is that, for intra-mesh
traffic, the protocol unnecessarily overloads the root which leads to scalability
problems.
- The Optimized Tree-based Routing (OTR) protocol [ 46 ] improves on the
TBR protocol by allowing for multiple gateways instead of the single gateway
assumption of TBR. As well, OTR divides the tree into pieces and the route is
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