03-08-2012, 04:27 PM
Wireless Mobile Ad Hoc Networks
1Wireless Mobile.ppt (Size: 2.57 MB / Downloads: 38)
Introduction
Two types of wireless networks:
infrastructured network:
base stations are the bridges
a mobile host will communicate with the nearest base station
handoff is taken when a host roams from one base to another
ad hoc network:
infrastructureless: no fixed base stations
without the assistance of base stations for communication
Due to transmission range constraint,
two MHs need multi-hop routing for communication
quickly and unpredictably changing topology
Mobile Ad Hoc Networks
Formed by wireless hosts which may be mobile
Without (necessarily) using a pre-existing infrastructure
Routes between nodes may potentially contain multiple hops
Many Applications
Personal area networking
cell phone, laptop, ear phone, wrist watch
Military environments
soldiers, tanks, planes
Civilian environments
taxi cab network
meeting rooms
sports stadiums
boats, small aircraft
Emergency operations
search-and-rescue
policing and fire fighting
Many Variations
Fully Symmetric Environment
all nodes have identical capabilities and responsibilities
Asymmetric Capabilities
transmission ranges and radios may differ
battery life at different nodes may differ
processing capacity may be different at different nodes
speed of movement
Asymmetric Responsibilities
only some nodes may route packets
some nodes may act as leaders of nearby nodes (e.g., cluster head)
Challenges
Limited wireless transmission range
Broadcast nature of the wireless medium
Packet losses due to transmission errors
Mobility-induced route changes
Mobility-induced packet losses
Battery constraints
Potentially frequent network partitions
Ease of snooping on wireless transmissions (security hazard)