Adaptive Clustering for Mobile Wireless networks
Adaptive Clustering.ppt (Size: 491 KB / Downloads: 73)
Mobile Ad hoc Network (MANET)?
A Mobile Ad hoc Network (MANET) is an autonomous system of nodes called mobile stations (MSs) connected by wireless links.
A MANET does not necessarily need support from any existing network infrastructure like an Internet gateway or other fixed stations.
The network’s wireless topology may dynamically change in an unpredictable manner since nodes are free to move.
Information is transmitted in a store-and forward manner using multi hop routing.
Each node is equipped with a wireless transmitter and a receiver with an appropriate antenna.
We assume that it is not possible to have all nodes within each other’s radio range.
When the nodes are close-by i.e., within radio range, there are no routing issues to be addressed.
At a given point in time, wireless connectivity in the form of a random multi-hop graph exists between the nodes.
Characteristics of Ad Hoc Networks
Dynamic topologies: Network topology may change dynamically as the nodes are free to move.
Bandwidth-constrained, variable capacity links: Realized throughput of wireless communication is less than the radio’s maximum transmission rate. Collision occurs frequently.
Energy-constrained operation: Some nodes in the ad hoc network may rely on batteries or other exhaustible means for their energy.
Limited physical security: More prone to physical security threats than fixed cable networks.
Virtual navigation: Data from a remote database is transmitted periodically in small relevant blocks using links present in the path of the automobile. This database may contain the graphical representation of streets, buildings, maps and the latest traffic information, which may be used by the driver to decide on a route.
Tele-medicine: Conference assistance from a surgeon for an emergency intervention.
Tele-Geo processing: Queries regarding location information of the users.
Crisis-management: Natural disasters, where the entire communication infrastructure is in disarray.
Education via the internet
Routing in MANETS - Goals
Provide the maximum possible reliability - use alternative routes if an intermediate node fails.
Choose a route with the least cost metric.
Give the nodes the best possible response time and throughput.
Route computation must be distributed. Centralized routing in a dynamic network is usually very expensive.
Routing computation should not involve the maintenance of global state.
Every node must have quick access to routes on demand.
Each node must be only concerned about the routes to its destination.
Broadcasts should be avoided (highly unreliable)
It is desirable to have a backup route when the primary route has become stale.
TORA not designed to find shortest path
TORA uses paths close to optimum when node mobility is low
Proposed a highly adaptive distributed routing algorithm that well-suited in mobile wireless networks
Decouple the generation of far-reaching control message propagation from the dynamics of the network topology
Possible enhancement would be to periodically propagate refresh packets outwards from the dest.
The refresh process permits intro of far-reaching control message propagation into the protocol independent of the network topology