wilamowski-b-m-irwin-j-d-industrial-communication-systems-2011

Routing in Wireless Networks 4-7
Firstly, due to the relatively large number of sensor nodes, it is not possible to build a global addressing
scheme for the deployment of a large number of sensor nodes as the overhead of ID maintenance is high.
Therefore, classic IP-based protocols cannot be applied to sensor networks.
Secondly, in contrast to typical communication networks, almost all applications of sensor networks
require the flow of data from multiple sources to a particular base station.
Thirdly, sensor nodes are tightly constrained in terms of energy, processing, and storage capacities
and this must be considered when designing a routing protocol. The next consideration is that in most
application scenarios, nodes in WSNs are generally stationary after deployment except for a few mobile
nodes. The next characteristic is that sensor networks are application specific (the requirements change
according to the application). Position awareness of sensor nodes is also important since data collection
is normally based on the location. Finally, data collected by many sensors in WSNs is typically based
on common phenomena, so there is a high probability that this data has some redundancy. This characteristic
must be used by the routing protocols to improve energy and bandwidth utilization [AK04].
Due to such differences, many new algorithms have been proposed for the problem of routing data in
sensor networks. The three main categories are flat, hierarchical, and location based, although there are
several others based on network flow or quality of service (QoS) awareness.
4.4.1 Flat Routing Protocols
In flat networks, each node normally plays the same role and sensor nodes collaborate to perform the
sensing task. Due to the large number of nodes, it is not feasible to assign a global identifier to each node.
This consideration has led to data-centric routing, where the base station sends queries to certain regions
and waits for data from the sensors located in the selected regions. Since data are being requested through
queries, attribute-based naming is necessary to specify the properties of data.
4.4.2 Hierarchical Routing Protocols
The hierarchical routing protocols use methods originally proposed in wireline networks. These are
well-known techniques with special advantages related to scalability and efficient communication. The
concept of hierarchical or cluster-based routing is also utilized to perform energy-efficient routing in
WSNs. In this type of architecture, higher-energy nodes are used to process and send the information,
while low-energy nodes can be used to perform the sensing in the proximity of the target. The creation
of clusters and assigning special tasks to cluster heads can greatly contribute to overall system scalability,
lifetime, and energy efficiency.
4.4.3 Location-Based Routing Protocols
Sensor nodes that use this routing protocol are addressed by means of their location. The distance
between neighboring nodes is estimated according to signal strengths. Coordinates of the neighboring
nodes can be obtained by exchanging information between neighbors. Some protocols use GPS to find
the location of neighboring nodes. In order to save energy in some location-based schemes, the nodes
that are not active go into sleep mode.
4.5 Summary of the Main Routing Protocols
in Wireless Networks
The most common MANET routing protocols are described in this chapter. These are promoted by the
IETF MANET Working Group by publishing them as experimental RFC, and are OLSR, Topology dissemination
Based on Reverse Path Forwarding (TBRPF), AODV, and Dynamic Source Routing (DSR).
© 2011 by Taylor and Francis Group, LLC