.FLYINGHEAD WIRELESS INFRASTRUCTURE
.TITLE Routing misbehavior in mobile ad-hoc networks
.AUTHOR Humayun Bakht
.SUMMARY One of the fundamental functions of a network is the transfer of data packets from one location to another, or routing. The absence of a fixed infrastructure makes routing a challenge a mobile ad-hoc environment. In this article, Contributing Editor Humayun Bakht show you what causes routing problems and how you can overcome these challenges in a mobile ad-hoc network.
.DEPT
Routing is the transfer of data packets from one location to another, and it’s one of the fundamental network functions. Network throughput, which is the ratio of data packets sent and received, is directly related to the routing function of any network. In other words, if the routing function is good enough, then we can expect a better output from the network. In today’s environment, we see different types of networks. Figure A shows one type of network, a traditional fixed computer network.
.FIGPAIR A Here’s what a traditional fixed network looks like.
Another type of network is a wireless network, which you can see in Figure B. Other than a wireless network, which depends on some sort of supporting structure for normal communication operations, mobile ad-hoc networks are short range wireless network provide communication services without the support of any centralized structure.
.FIGPAIR B This figure illustrates how wireless networks work.
Routing in mobile ad-hoc networks is achieved through mobile nodes acting as intermediate nodes. These nodes are responsible for receiving and forwarding data packets from one host to another in the network. The absence of a fixed infrastructure makes routing a challenge in a mobile ad-hoc environment.
There are also several other issues which have an effect on the overall performance of the mobile ad-hoc network. Some of these issues include bandwidth constraints, hidden terminal problems, security and limited battery power of the participating nodes. These issues are somehow interrelated with the overall routing mechanism. In order to gain a better routing solution, it’s almost always required to address these issues in conjunction with the routing problem of the mobile ad-hoc network.
Within the traditional routing mechanism, there are also several other issues to consider. For example, a node can become selfish and refuse to forward data packets to other nodes; or the node fails to forward data packets to the destination node. Finally, a node could enter an an inactive state because of a limited power supply. These are some of the issues can result in communication breakdowns and can eventually lead us to an abnormal network environment.
Let’s consider when a node refuses to forward data packets to the other nodes. There are number of approaches you can take that would solve this problem. These solutions could involve an initial mutual agreement which can force all intermediate nodes to act as intermediate nodes without refusing to forward any data packet which comes to them.
Although no centralized scheme exists in mobile ad-hoc networks, it could be a better routing strategy to appoint a particular node as a central node. The appointed node then will hand various other jobs which are not required from other nodes of the network. You can use the central node for any such agreement. Another solution is to track down the node that’s acting as a selfish node. Once this node has been identified, all other connections with this particular node could be dropped, followed by the re-establishment of all the routes.
The situation where a node cannot forward data packets because of battery failure can be resolved by choosing a battery supply which can last longer. Another solution might be to agree on a certain power limits where all nodes can be considered as an active. As soon as a node power supply drops below the agreed limit, this connection can be considered as the risky one. All other routes under this condition can be reorganized.
One final suggestion is to include the voluntary services from all the participating nodes. Whenever a node approaches a low battery power limit, it can broadcast an information packet to all the other nodes in the network. This packet must contain information such as next hop neighbors, node ID, or sequence number which can assist other nodes readjust their routing tables and the whole network could be reorganized.
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In summary, where routing itself a core challenge in mobile ad-hoc networks, there are still some threats even to the existing traditional routing mechanisms as adopted by mobile ad-hoc network. We have discussed some existing routing issues and have suggested some of the possible solutions.
Although there’s more of a focus on a routing mechanisms for mobile ad-hoc network, very little attention has been given to make conventional routing mechanisms effective. The solutions covered in this article could possibly help to improve the performance of basic routing mechanism as in use for routing in mobile ad-hoc networks.
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