Mobile Ad-hoc Network (MANET)
Wednesday, 17. January 2007, 06:18:03
Overview
A mobile ad-hoc network (MANET) is a kind of wireless ad-hoc network, and is a self-configuring network of mobile routers (and associated hosts) connected by wireless links—the union of which form an arbitrary topology. The routers are free to move randomly and organise themselves arbitrarily; thus, the network's wireless topology may change rapidly and unpredictably. Such a network may operate in a standalone fashion, or may be connected to the larger Internet.
Mobile ad-hoc networks became a popular subject for research as laptops and 802.11/Wi-Fi wireless networking became widespread in the mid- to late 1990s. Many of the academic papers evaluate protocols and abilities assuming varying degrees of mobility within a bounded space, usually with all nodes within a few hops of each other, and usually with nodes sending data at a constant rate. Different protocols are then evaluated based on the packet drop rate, the overhead introduced by the routing protocol, and other measures.
The MIT Media Lab $100 laptop program hopes to develop a cheap laptop for mass distribution (>1 million at a time) to developing countries for education. The laptops will use ad-hoc wireless mesh networking to develop their own communications network out of the box.
Vehicular ad-hoc networks or VANETs are a form of MANETs used for communication among vehicles and between vehicles and roadside equipment.
Routing
Routing within a MANET is different from traditional routing in wired network.
There is no infrastrcure within a MANET and dedicated router. Each node has to do routing, behaving as a host and a router.
The topology may change at any time, so routing has to reach convergence in a short period of time. And because wireless medium has a limited bandwidth, and MANET nodes may run on battery, routing mechanism with high overhead will not be a good choice for MANET. There are mayor reasons that traditional routing protocols are not suitable for MANET.
Considering the factors mentioned above, on-demand routing protocols are competitive candidates. They only perform routing process while the application layer has data to send, if not, they will stay silent. Examples are DSR, AODV, TORA, etc.
But there are indeed proactive routing protocols. One example is OLSR, which maintains neighbor relation by sending periodical Hello messages and keeps a link-state route database constantly, no matter the user application layer wants to send data or not.
By first look, we may take on-demand routing as more reasonable for MANET. Interestingly, however, proactive OLSR is an Internet standard defined in RFC 3626, while the well known on-demand routing protocols haven't reached standard status. DSR and TORA are still draft, while AODV is an Internet experimental protocol.
A mobile ad-hoc network (MANET) is a kind of wireless ad-hoc network, and is a self-configuring network of mobile routers (and associated hosts) connected by wireless links—the union of which form an arbitrary topology. The routers are free to move randomly and organise themselves arbitrarily; thus, the network's wireless topology may change rapidly and unpredictably. Such a network may operate in a standalone fashion, or may be connected to the larger Internet.
Mobile ad-hoc networks became a popular subject for research as laptops and 802.11/Wi-Fi wireless networking became widespread in the mid- to late 1990s. Many of the academic papers evaluate protocols and abilities assuming varying degrees of mobility within a bounded space, usually with all nodes within a few hops of each other, and usually with nodes sending data at a constant rate. Different protocols are then evaluated based on the packet drop rate, the overhead introduced by the routing protocol, and other measures.
The MIT Media Lab $100 laptop program hopes to develop a cheap laptop for mass distribution (>1 million at a time) to developing countries for education. The laptops will use ad-hoc wireless mesh networking to develop their own communications network out of the box.
Vehicular ad-hoc networks or VANETs are a form of MANETs used for communication among vehicles and between vehicles and roadside equipment.
Routing
Routing within a MANET is different from traditional routing in wired network.
There is no infrastrcure within a MANET and dedicated router. Each node has to do routing, behaving as a host and a router.
The topology may change at any time, so routing has to reach convergence in a short period of time. And because wireless medium has a limited bandwidth, and MANET nodes may run on battery, routing mechanism with high overhead will not be a good choice for MANET. There are mayor reasons that traditional routing protocols are not suitable for MANET.
Considering the factors mentioned above, on-demand routing protocols are competitive candidates. They only perform routing process while the application layer has data to send, if not, they will stay silent. Examples are DSR, AODV, TORA, etc.
But there are indeed proactive routing protocols. One example is OLSR, which maintains neighbor relation by sending periodical Hello messages and keeps a link-state route database constantly, no matter the user application layer wants to send data or not.
By first look, we may take on-demand routing as more reasonable for MANET. Interestingly, however, proactive OLSR is an Internet standard defined in RFC 3626, while the well known on-demand routing protocols haven't reached standard status. DSR and TORA are still draft, while AODV is an Internet experimental protocol.
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