Lecture 7

1. Wireless Ad Hoc and Sensor Networks
CSE 5109
Sajeeb Saha
Assistant Professor
Dept. of CSE, JnU

2. Wireless Ad Hoc Routing
Protocols
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3. What is Routing?
– The process of moving a packet of data from source to
destination.
– Routing is usually performed by a dedicated device called
a router.
– Each intermediary computer performs routing by passing
along the message to the next computer.
– Part of this process involves analyzing a routing table to
determine the best path.
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4. Common objective:
Route packets along the optimal path
– Routing protocols adapt to changing network conditions and by
definition offers multi-hop paths
– Routing protocols differ in route table
 construction
 maintenance
 update
Next-hop routing protocols can be categorized as:
– Link-state
– Distance-vector
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Purpose of Routing

5. – [Dijkstra 1959 and McQuillan+ 1980]
– Traditional link-state protocols may not be suitable
– Closer to centralized version of shortest-path algorithm
– Each node maintains a view of network topology with a cost for each link
– Link costs are broadcast periodically to keep the views consistent
– Each node updates its view and applies a shortest-path algorithm to find its
next hop for each destination
– Routing loops may occur due to propagation delays, partitioned networks, and
so on
– Alternative link-state routing approaches may not require all nodes to have
the identical link-state information and route selection algorithms and may find
routes on demand
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Link State Routing
Distributed database problem

6. – [Ford+ 1962 and Leiner+ 1987]
– Based on shortest-path routing algorithms i.e., Distributed Bellman-
Ford
– DBF algorithms are also known as Distance-Vector (DV)
– Routers exchange their distances to known destinations;
– a router uses the distance vectors received from its neighbors to
compute its own distances.
– For each destination, the node stores a single route table entry along
with next-hop neighbor
– Route table entry for destination contains metric which is distance
from node to the destination and also the next-hop (vector) towards
destination
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Distance Vector Routing
Distributed computation problem

7. • Mobility
– Induced route changes
– Induced packet losses
– frequent network partitions
• Error-Prone Shared Broadcast Radio Channel
– Hidden/Exposed terminal problem
– Packet losses due to transmission errors
• Bandwidth Constraint
– Less data rate
– Minimum Control Information
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Challenges in Wireless Ad Hoc Routing

8. • Resource Constraint
– Battery Life
– Processing Power
• Security Hazard
– Ease of snooping on wireless transmissions
– Ease of denial-of-service attack
– Misbehaving nodes difficult to identify
– Nodes can be easily compromised
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Challenges in Wireless Ad Hoc Routing

9. 1. The routing protocol should be Distributed.
2. It must be adaptive to frequent topology changes.
3. Route computation and maintenance must involve a minimum
number of nodes.
4. It must be Localized.
5. The routes must be loop-free and stale-free.
6. The number of packet collisions must be kept to a minimum.
7. It must converge to a optimal route.
8. It must optimally use scarce resources such as bandwidth,
computing power, memory, and battery power.
9. It should be able to provide a certain level of quality of service
(QoS)
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Wireless Ad Hoc Routing Requirements

10. Ad-Hoc Mobile
Routing
Protocols
Table Driven /
Proactive
Hybrid
On-Demand-
Driven /
Reactive
DSDV
GSR
FSR
HSR
ZHLS
CGSR
WRP
AODV
DSR
TORA
CBRP
ABR
SSR
ZRP
Cluster
OLSR
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Wireless Ad Hoc Unicast Routing Protocols

11. Table Driven Routing Protocol
– proactive!!
– continuously evaluate the routes
– attempt to maintain consistent, up-to-date routing
information
• when a route is needed, one may be ready
immediately
– when the network topology changes
• the protocol responds by propagating updates
throughout the network to maintain a consistent
view
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12. • Proactive: maintain routing information
independently of need for communication
• Update messages send throughout the network
periodically or when network topology changes.
• Low latency, suitable for real-time traffic
• Bandwidth might get wasted due to periodic
updates
• They maintain O(N) state per node, N = #nodes
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Table Driven Routing Protocol

13. • DSDV – Destination-Sequenced Distance
Vector
• WRP – Wireless Routing Protocol
• GSR – Global State Routing
• FSR – Fisheye State Routing
• HSR – Hierarchical State Routing
• ZHLS – Zone-based Hierarchical Link State
Routing Protocol
• CGSR – Clusterhead Gateway Switch Routing
Protocol
Table Driven Routing Protocol

14. – reactive!!
– on-demand style: create routes only when it is
desired by the source node
• route discovery: invoke a route-determination
procedure
• the procedure is terminated when
– a route has been found
– no route is found after all route permutations
are examined
– longer delay: sometimes a route may not be ready
for use immediately when data packets come
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On Demand Routing Protocol

15. • Reactive: discover route only when you need it
• Saves energy and bandwidth during inactivity
• Can be bursty -> congestion during high activity
• Significant delay might occur as a result of route
discovery
• Good for light loads, collapse in large loads
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On Demand Routing Protocol

16. • AODV – Ad Hoc On-demand Distance
Vector Routing
• DSR – Dynamic Source Routing
• TORA – Temporally Ordered Routing
Algorithm
• CBRP – Cluster Based Routing Protocols
• ABR – Associativity Based Routing
• SSR – Signal Stability Routing
On Demand Routing Protocol

17. Hybrid Routing Protocols
• Proactive for neighborhood, Reactive for far
away (Zone Routing Protocol, Haas group)
• Proactive for long distance, Reactive for
neighborhood (Safari)
• Attempts to strike balance between the two
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18. Hierarchical Routing
• Nodes are organized in clusters
• Cluster head “controls” cluster
• Trade off
– Overhead and confusion for leader election
– Scalability: intra-cluster vs intercluster
• One or Multiple levels of hierarchy
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19. Geographical Routing
• Nodes know their geo coordinates (GPS)
• Route to move packet closer to end point
• Protocols DREAM, GPSR, LAR
• Propagate geo info by flooding (decrease
frequency for long distances)
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20. Ad Hoc Wireless Networks:
Architectures and Protocols
• Chapter 7
Suggested Reading
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21. THANK YOU