26-07-2014, 03:52 PM
Challenges in Mobile Adhoc Network Routing and their Solutions using Ant Colony Optimization Technique
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INTRODUCTION
Mobile Ad-hoc Network (MANET) is a dynamic wireless network with or without fixed infrastructure. Nodes move freely and arrange themselves randomly.
One of the major issues in MANET is routing due to the mobility of the nodes.
Routing means the act of moving information across an internet work from a source to a destination.
When it comes to MANET, the complexity increases due to various characteristics like
Dynamic topology
Time varying QoS requirements
Limited resources and energy
Nature-inspired algorithms (swarm intelligence) such as ant colony optimization (ACO) algorithms have shown to be a good technique for developing routing algorithms for MANETs.
ROUTING
It is the process of sending a packet of data from source to destination .
It is usually performed by a dedicated device known as router which enables messages to pass from one computer to another and eventually reach the target machine.
Each intermediary system performs routing by passing along the message to the next system .
MOBILE ROUTING
IP assumes end hosts are in fixed physical locations
IP addresses enable IP routing algorithms to get packets to the correct network
What if a hosts moves to a different network?
Two solutions:
The host carries the old IP address. Maintain host-specific routes for all mobile hosts on all routers. Not scalable, because of too many individual routes need to be maintained.
Change IP address of the mobile host to an address in the new network. Upper layer connections (such as TCP) will break. Also, not easy to find IP address for a mobile host that moves frequently
MOBILE IP
Mobile IP solution : Preserve the original address, but also use a new care-of-address (COA).
Mobile IP was developed as a means for transparently dealing with problems of mobile users
Enables hosts to stay connected to the Internet regardless of their location
Enables hosts to be tracked without needing to change their IP address
Requires no changes to software of non-mobile hosts/routers
Requires addition of some infrastructure
Has no geographical limitations
Requires no modifications to IP addresses or IP address format
Supports security
TABLE DRIVEN PROACTIVE ROUTING
This type of protocols maintains fresh lists of destinations and their routes by periodically distributing routing tables throughout the network.
The main disadvantages of such algorithms
are :
Respective amount of data for maintenance.
Consumption of more bandwidth.
ON DEMAND REACTIVE ROUTING
This type of protocols finds a route on demand by flooding the network with Route Request packets.
The main disadvantages of such algorithms are:
High latency time in route finding.
Excessive flooding can lead to network clogging.
FLOW ORIENTED ROUTING
This type of protocols finds a route on demand by following present flows.
One option is to unicast consecutively when forwarding data while promoting a new link.
The main disadvantages are :
Exploring new routes without prior knowledge takes a long time
May refer to entitative existing traffic to compensate for missing knowledge on routes
CONSTANTLY CHANGING TOPOLOGY
Due to the continuous motion of nodes, the topology of the mobile ad hoc network changes constantly: the nodes can continuously move into and out of the range of the other nodes in the ad hoc network, and the routing information will be changing all the time because of the movement of the nodes.
SCALABILITY
The scale of the ad hoc network keeps changing all the time: because of the mobility of the nodes in the mobile ad hoc network, you can hardly predict how many nodes there will be in the network in the future.
As a result, the protocols and services that are applied to the ad hoc network such as routing protocol and key management service should be compatible to the continuously changing scale of the ad hoc network, which may range from decades of nodes to hundreds of nodes, or even thousands of nodes