21-09-2013, 01:05 PM
Routing in Wireless Ad Hoc Networks
Wireless Ad Hoc Networks[.pdf (Size: 452.6 KB / Downloads: 21)
Mobile Ad hoc NETworks (MANETs)
• Autonomous system of
mobile routers connected by
wireless links, forming an
arbitrary graph
• Developed within the IETF
(Internet Engineering Task
Force) to extend the Internet
technology to mobile
networks
(MANETs)
• Nodes are computing and
communication devices, e.g laptops,
PDAs, mobile phones,even sensors
• Nodes organize and maintain the
network by themselves
• A node is both a host and a router
• First and foremost issue: routing
Proactive approach, e.g., DSDV , OLSR
1. Based on DV and LS, where each node has
complete/global knowledge of network
2. Node acts as host and router
3. When route changed, propagate update through
network
4. Good for connectionless traffic, where data can be
transferred at any time to any node, where each node
has a global knowledge of network
Reactive approach, e.g., AODV , DSR
1. Route ONLY created when needed by source node
2. So, NO need for global/complete knowledge of
network
3. Route discovery ends when route is discovered, or
when all possible paths are examined.
4. After route is established, route is maintained using
route maintenance protocol
Distance Vector Routing (1)
• Each node has a routing table where distance to all
reachable destinations are recorded
– Each node is responsible for keeping track and
informing its neighbors of its distance to each
destination
• A router computes its distance to a destination based
on its neighbors distance to the destination
Problems with Distance Vector
• Does not scale well with the number of nodes
in the network
• Slow convergence to the lowest cost route
• Slow recovery time if there are link failures,
and, hence, routing problems during disruption
times
• Count-to-infinity: Router loops may take
place