Routing in Wireless Sensor Networks

Elet-6316: Routing Algorithms & Protocols
Dr. Driss Benhaddou

By: Syed Ashar Zia

 Phase I: Introduction to Wireless
sensor networks, its applications,
architecture, and
challenges.

 Phase II: Routing Protocols
introduction,
DSDV, AODV, Cluster-based
routing.

 Phase III: Performance evaluation of
AODV and DSDV through
BY: SYED ASHAR ZIA 2

 WSN refers to a network of sensor nodes
connected through wireless medium.
 WSN is usually a large network
connecting even more than a thousand
nodes.
 Sensor nodes are used to monitor, record
and notify specific conditions at various
locations.
 Conditions could be
temperature, humidity, wind, pressure, an

 WSN has a wide range of applications,
such as:
 Military applications,
 Environmental monitoring,
 Industrial sensing,
 Security applications.
 WSN is very useful for monitoring
remote locations where human access
is limited or not possible at all.


Fig: Sensor Network with Internet access


 Sensor nodes/End nodes
 Responsible for sensing the conditions.
 Base Station/Sink node
 Collects information from end-nodes.
 Gateways
 Processing Hub
 Processes the collected data at BS.
 Storage Hub


 Three layers are added
in TCP/IP model.

 To increase the
awareness at the
nodes.

 Task, Mobility & Power
are crucial information
in sensor networks.


 Architecture
 Energy efficient architecture is priority.
 Compromises could be made on size,
capacity, cost & speed.

 Routing
 Different from the traditional IP Networks.
 Talking to thousands of nodes makes it
complex and inefficient at the energy &
storage level.


 Distributed Signal Processing
 Important part at the low-level layer in WSN.
 Provides BS with locations & signal
identification of nodes, etc.

 Storage & Data retrieval
 Central storage of data from several nodes.
 Storage at nodes requires processing at the
nodes.


 Actuation
 Required action for sensed quantity.
 Such as pointing cameras, alarming sounds,
opening valves, etc.

 Security
 Attackers may change the behavior of nodes
leading to change in results.
 Confidentiality, integrity, robustness, and
authenticity matters in WSN.


Routing in WSN

Network Protocol
Structure Operation

Flat Hierarchical Location Negotiation Multi-path Query
QoS based
Networks Networks based based based based


 WSNs are usually ad-hoc in nature.
 Nodes’ communication directly to BS
defines their MANET (Mobile Ad-hoc
Network) nature.
 Set of standards are defined for the
protocols used in Ad-hoc networks
 Mobility of nodes disturbs the
standards, therefore routing is quiet
challenging.


Proactive/Table
DSDV, FSR, STAR
Driven

Hybrid ZRP

Routing Protocols
for MANET
Reactive/
DSR, AODV, TORA
On-demand Driven

Cluster-based LANMAR, CEDAR


 Pro-Active Protocols
 Routing table with all paths maintained at
each node.
 E.g. DSDV (Direct Sequenced Distance
Vector)
 Reactive Protocols
 Discovers route when required.
 E.g. AODV (Ad-hoc On-demand Distance
Vector)
 Hybrid
 Combination of Proactive ZIA Reactive
BY: SYED ASHAR
& 18

 Each node maintains a routing table
containing
 List of all available destinations
 Number distance to each each destination
 Next hop to reach a destination
 The succession of next hops leads to a
destination
 Each node periodically broadcasts its current
estimate of the shortest distance to each
available destination to all of its neighbors
 Typical representative: Distributed Bellman-

 Design Goals
 Keeping the simplicity of Bellman-Ford.
 Avoid looping issues
 Route information is transmitted by
broadcast
 Updates are transmitted periodically or
immediately when any significant topology
change is available
 Even sequence no.s are assigned by
destination
 If a broken link is detected: metric ∞ and
updated odd sequence no. are assigned by
detecting host. BY: SYED ASHAR ZIA 21

 Types of Broadcast updates
 Full Dump: All information from the
transmitting node.
 Incremental: All information that has
changed since the last full
dump.
 Full dump is transmitted if incremental dump
exceeds the size of one NPDU.
 Routing Table is maintained with latest
sequence numbered route and least
cost metric.

 Excellent performance in small
networks.
 Energy efficient as route processing is
minimal.
 Routing overhead is approximately
constant regardless of node movements
and traffic load.
 Simple implementation using Bellman-
Ford algorithm.


 Bandwidth and size of table increases
with increasing number of nodes.
 Overhead increases for maintaining
large no. of nodes, hence degrades the
performance of network.
 Fails to converge if nodes are changing
locations quickly.
 Not very efficient in route updating.
 Limits no. of nodes that can join network.


 Intended for the networks with thousands
of nodes.
 It’s a reactive or demand-driven protocol
which calculates the route when required
and caches it for further use.
 Routing table only maintains next hop for
the destination rather than complete
route.
 Freshness of route is maintained by
sequence numbers.

 Routing Table maintains:
 Destination IP address
 Destination sequence number
 Valid destination sequence number flag
 Other state & routing flags
 Network interface
 Hop count
 Next hop
 Lifetime (route expiration time)


 Basic message set
in AODV includes:
 Hello - For link status
 RREQ - Route
Request
 RREP - Route Reply
 RERR - Route Error

 Only in case of
Route is not in table
and has to be
discovered.

A
B?

B?
B?
B?

B?
B? B?

B

 Maintenance of Routes is handled very
efficiently in AODV
 Hello messages broadcast by active nodes
periodically called HELLO_INTERVAL.
 If no Hello reply from a neighbor within
DELETE_PERIOD link failure is identified.
 RERR message is broadcasted to other
neighbors.
 Entries based on that node invalidated.
 Route is rediscovered using RREQ when it is
required.


Simulation done by:
Abdul Hadi Abd Rahman & Zuriati Ahmad Zukarnain
European Journal of Scientific Research

Scenario 1: End-to-End Delay with increasing number of nodes.

In AODV graph fluctuates between 0.3 and 2.4sec while in DSDV it is between
0.005 and 0.008 sec. This shows that route calculation or discovery method in
AODV increases the End-to-End delay.


Scenario 2: Routing Overhead with increasing number of nodes.

Here, three routing protocols are compared, AODV, DSDV and Improved
DSDV. Here, we can see that with increasing no. of nodes routing overhead
increases dramatically in DSDV which causes instability when it’s a large
network.

 Small WSN:
 DSDV is better than AODV.
 Less routing overhead
 Delay is negligible when compared to the
time it takes to calculate route in AODV.
 Large WSN:
 AODV is better than DSDV
 Efficiently handles mobility and route
updates.
 Less overhead and appropriate delay.

 Routing in Wireless sensor networks – Rachid
Ennaji & Muhammad Boulmalf – IEEE, 2009
 Performance comparison of AODV, DSDV and I-
DSDV – Abdul Hadi & Zuriati Ahmed – European
Journal of Sc. Research
 Group-based clustering RP – Lei Zhang – IEEE,
2007
 http://www.ece.ul.ie/homepage/tom_newe/RFP05.
html
 http://www.ece.gatech.edu/research/labs/bwn/WM
SN/projectdescription.html
 www.authorstream.com

Routing in Wireless Sensor Networks

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