05-11-2012, 04:30 PM
Routing in Mobile Ad-Hoc Networks
Routing in Mobile Ad-Hoc.ppt (Size: 156.5 KB / Downloads: 120)
Towards MANETs
Networking wireless hosts:
Cellular Networks
Infrastructure dependent
High setup costs
Large setup time
Reliable
Some motivating applications:
Casual conferencing
low set-up time, cost preferred
Battlefield operations/disaster relief
infrastructure unavailable
Personal area networking
devices around the home/office
Cellular networks are not preferred.
Dynamic Source Routing (DSR)
Routing is through source routing
complete path with each packet
Route discovery
flooding RREQ till a node replies
Route maintainance
explicit link breakage notification
Mobility of a node can break routes passing through it.
Destination Sequenced Distance Vector (DSDV)
Modified Distance Vector protocol
periodic DV updates
High frequency of DV updates
topology is dynamic
Does not scale well
size of DV updates increase
high routing overheads
The Dynamic Virtual Backbone
The dynamic virtual backbone is a concept wherein a set of relatively stable routes are formed despite nodes being mobile.
a possible way is to abstract mobility through aggregation
a dynamic group of nodes by preventing some information from moving out of the group, keeps mobility transparent to the rest of the network.
Kelpi
Kelpi: a MANET routing algorithm based on the concept of Virtual Backbone Routing (VBR).
Assumptions:
nodes equipped with positioning system, say a GPS receiver
nodes capable of multi-level transmission
mobility scenario
upto vehicular speeds of mobility
area of a few kilometres
fairly dense network
typical battlefield/disaster relief scenario
Kelpi: Route Discovery
node S wants to send to node D
S must know D’s cell
S discovers D’s cell by sending a FIND_CELL packet to its router
Routers flood FIND_CELL among themselves
A router with the node in its node_list replies directly to S
Implementation
ns-2 network simulator used for implementing Kelpi
open source, used widely in MANET research
critical modifications to ns-2
packet headers
physical layer code for multi-powered transmitter
introduction of new routing agent: Kelpi
Kelpi vs. other algorithms
Advantages
designed to provide stable routes
increased throughput due to two levels of transmission
reduced flooding overhead
Disadvantages
positioning system required
muliple levels of transmission preferred
routers may be overloaded in a dense network