.FLYINGHEAD WIRELESS INFRASTRUCURE
.TITLE Power aware routing for mobile ad-hoc networks
.AUTHOR Humayun Bakht
.SUMMARY Contributing Editor Humayn Bakht continues his quest to educate Computing Unplugged’s readers about mobile ad-hoc networks. In this article, he examines why routing data is important and two methods that can gauge how much power is used to transmit data.
.DEPT
Routing is one of the fundamental aspects of any network. Routing can be defined as a process of packet exchange between various hosts in a network. In traditional networks, including those wireless networks which operate with the help of some supporting structure, routing is normally carried out by various network devices such as routers and base stations. Sadly, these devices are not very helpful for routing in mobile ad-hoc networks.
Mobile ad-hoc networks are short-lived networks which are formed to connect various wireless devices to each other without a fixed infrastructure. Recent advances such as Bluetooth and WiFi are a couple of example of how mobile ad-hoc networks could be implemented.
The absence of a fixed supporting structure makes mobile ad-hoc networks capable of providing various network operations in places where a fixed infrastructure would normally be destroyed. Some of the possible application areas of these networks are disaster recovery, sensor networks, and various military operations.
In reality, one of the basic aspects of such a network formation is to help carry out various network operations in a battle field. Ad-hoc networks were later implemented in wider projects by DARPA (Defense Advanced Research Projects Agency), which is why these networks are sometimes called DARPA packets radio networks. The current research in this area highlights some of the challenges. These weaknesses are one of the main hassles in the implementation of ad-hoc network at a large scale. Some of these weaknesses include routing, low bandwidth, power constraints, security and hidden terminal problem.
Where on one hand, routing requires some specific techniques to be developed to route packets between two mobile nodes of mobile ad-hoc network, bandwidth constraints requires routing techniques to be less congested. These techniques must consume less power and provide a secure routing transmission. These challenges make routing in a mobile ad-hoc network an interesting issue. Work in this area started a decade ago and to date there a number of different routing solutions have been proposed. One of the main drawbacks is that consideration hasn’t been given to address routing in conjunction with the above mentioned issues. That’s why while we find these solutions are good in handling some of these challenges, we find them lacking in addressing others.
With power aware routing for mobile ad-hoc networks, we find routing itself is a major problem. Why do we actually need a power aware routing solution for mobile ad-hoc networks? This is due to the fact that ad-hoc networks operate on low battery devices, and if we have routing solution which required all participating wireless devices to be continuously awake, the battery of these devices would run out. Obviously, it’s not feasible to have your transmission broken down because of low power availability. Plus, establishing an ad-hoc network from scratch is a time consuming topic which does involve other complexities. It’s almost crucial to have a power aware routing solutions specifically for mobile ad-hoc networks.
The existing routing solutions can broadly be classified into two main types: tables driven and on demand routing solutions. Tables driven protocols are considered to be some of the earlier efforts in proposing a separate routing solution for mobile ad-hoc networks. These protocols require all the mobile hosts to be continuously awake by sending topology updates to all other nodes at a regular intervals. That’s how they maintain a consistent overview of the entire network. Therefore, whenever a node is required to send information to other nodes, it drives the route information from the routing table and transfers this information to the destination node. The procedure is straight forward, especially in an environment which is highly dynamic. By highly dynamic, we mean nodes change their locations or topology continuously. There is very little doubt about the poor performance of these protocols not as a whole but in terms of power consumption. In my opinion, this approach cannot be regarded as a power aware routing technique.
On-demand protocols establish a routing path only when a transmission is required. In other words, if node A wants to transmit some information for node B, node A initiates a route discovery procedure. Once the route is found, data is transferred from A to B. Clearly, this approach is good, especially in terms of power saving. Moreover, some of these protocols allow nodes to go into sleep mode while they are not in an active transmission.
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In summary, power aware routing is an essential aspect in developing efficient routing techniques for mobile ad-hoc network. These types of techniques are required as most of the participating devices generally operate on low battery power. There is much effort has been done to deliver a routing solution which can not only route packet between two hosts in a mobile ad-hoc network but also consume less power. However there is still lot to do before these solutions could be implemented in a real environment, thereafter, can be use to deliver successful future ad-hoc network products.
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