This document discusses geographical routing in mobile ad hoc networks. It describes traditional routing approaches like next-hop routing, source routing, and flooding, and their disadvantages. It then introduces geographical routing, which uses location information to route packets. Key geographical routing protocols discussed include LAR, DREAM, and GRID. LAR and DREAM disseminate location information and forward packets towards the destination's expected zone. GRID partitions the area into grids and elects gateways to route between grids towards the destination. The document also categorizes geographical routing algorithms based on their use of location services, forwarding strategies, and recovery schemes.

1. Geographical
Routing

2. Introduction
 Basically there are 2 approaches of
routing
1. Traditional routing algorithm adapted for
Ad Hoc Networks
2. Geographical routing

3. Traditional routing techniques
 Next hop routing
 Source routing
 Flooding

4. Next-Hop routing
• The algorithm calculates the next hop
which is better to reach the destination.
• As the destination node changes, the next
hop also changes.
• In this way, the packet is sent from sender
to destination through 1 or more hops
which acts as intermediate nodes

5. Source Routing
x
b
a
c
y
Which path??

6. • In this type of routing, the algorithm
calculates the lowest cost path to reach
the destination.
• Here, various routes are tabulated and
the best path is selected to send the
packets.

7. Flooding
 In this type, each node sends the status of
its state to every other node. Hence the
information about all other nodes in the
network is upadated continuously.
 At the time of routing, the algorithm
selects the node which is currently
available and sends the packet.

8. Disadvantages
 Scalability
 Quick topology Changes

9. Geographical Routing
 It makes use of location information in
routing
 The location of both the sender and the
destination is known.

10. Assumptions
 Each node knows of its own location
• Outdoor positioning device
 GPS: Global Positioning System
 Accuracy: about 5 to 50 meters
• Indoor positioning device
 Infrared
 Short distance radio

11.  The destination location is also known by
using the following routing techniques
 LAR – Location Aided Routing
 DREAM – Distant Routing Effect Algorithm
for Mobility.
 GRID Routing

12. LAR – Location Aided Routing
 Location-Aided Routing (LAR) in mobile
ad hoc networks
 Young-Bae Ko and Nitin H. Vaidya
 Texas A&M University
 All packets carry sender’s current
location.
 This info enables nodes to learn of each
other’s location.

13. Basic idea of LAR
 Same as DSR, except that if the
destination’s location is known, the
ROUTE_REQ is only flooded over the
“route search zone.”
Expected
zone

14. DREAM
 A Distance Routing Effect Algorithm for
Mobility (DREAM)
 S. Basagni, I. Chlamtac, V.R. Syrotiuk, B.A.
Woodward
 The University of Texas at Dallas
 Dissemination of location information:
• Each node periodically advertises its
location (and movement information) by
flooding.
• This way, nodes have knowledge of one
another’s location.

15. Basic Idea of DREAM
 Data Packet carries D’s and S’s locations.
 Forwarded toward only a certain
direction.
D
Expected zone
of D

16. Grid Routing
 “GRID: A Fully Location-Aware Routing
Protocol for Mobile Ad Hoc Networks”
 Wen-Hwa Liao, Yu-Chee Tseng, Jang-Ping
Sheu
 Partition the physical area into d x d
squares called grids.

17. Protocol Overview
 In each grid, a leader is elected, called
gateway.
 Responsibility of gateways:
 forward route discovery packets
 propagate data packets to neighbor grids
 maintain routes which passes the grid
 Routing is performed in a grid-by-grid
manner.

18. S
D
q
(c) Fan( )q, r
r
S
D
S
D
(a) Rectangle
(d) Two_Fan( )q, r
(b) Bar(w)
w
S
D
q
q
r
Route Search Range Options

19. Gateway election in a grid
 Any “leader can be used.
 Multiple leaders in a grid are acceptable.
 Preference in electing a gateway:
 near the physical center of the grid
 likely to remain in the grid for longer time
 once elected, a gateway remains so until
leaving the grid
election” protocol in distributed computing

20. Taxonomy of Geographical
Routing Algorithms
 Also called position-based routing
 Three major components of geographic
routing:
 Location services (dissemination of location
information)
 Next topic
 Forwarding strategies
 Recovery schemes

21. Forwarding Strategies
 Basic greedy methods
 Directional flooding
 Geographical source routing
 Power-aware routing