.FLYINGHEAD WIRELESS INSFRASTRUCTURE
.TITLE Problems and solutions in mobile ad-hoc networks
.AUTHOR Humayun Bakht
.SUMMARY In this latest installment of his ongoing series addressing ad-hoc networks, Contributing Editor Humayun Bakht discusses some of the associated problems and their solutions.
.DEPT
We’re living in the age of information technology. All around us, we see revolutions in various forms. From wireless communication, to cellular phones, to withdrawals from cash machines, we encounter technological developments daily we couldn’t have imagined in the past.
Before we talk about wireless communication, there are two important concepts with which you must be familiar: front-end and back-end applications. Front-end and back-end are terms used to characterize program interfaces and services relative to the user of these interfaces and services.
A front-end application is one that application users interact with directly. A back-end application serves indirectly in support of the front-end services, usually by being closer to the required resource or having the capability to communicate with the required resource. The back-end application may interact directly with the front-end or, perhaps more typically, is a program called from an intermediate program that mediates front-end and back-end activities.
The wireless cellular system has been in use since the 1980s. Now, with advanced wireless systems, you can do online chatting, send pictures from one place to another, and if you can afford it, stay globally connected with friends, relatives, etc. all the time. This wireless cellular system reduces distances, offers better services, and makes us able to utilize many advance services more efficiently than before.
Here, the problem is our thirst for better and not with the system. For me, the system is fine, but yes there are some limitations. Adaptability is the core issue. Simply, how adaptable is the system under various environments? Will the system work even if the supporting structure crashes? Can the system work without dependency on any infrastructure? Does the system need an administrator to monitor the whole range of operations? Many other similar issues come up when we discuss the overall adaptability of fixed wireless communication systems.
An old concept, in modified form, has emerged with the invention of technologies like Bluetooth, WiFi, etc. This concept is known as the mobile ad-hoc, or peer-to peer network. The mobile ad-hoc network is one of the new additions in the family of wireless networks. It was first used on an experimental basis in the 1970s to run various military applications. Later, DARPA launched a project to monitor the feasibility of the concept of peer-to-peer networking.
.BREAK_EMAIL To learn more about the problems with ad-hoc networks, and their solutions, click here.
A mobile ad-hoc network is an autonomous system of mobile nodes connecting together in the absence of fixed infrastructure. Mobile ad-hoc networking is an advantageous way of exchanging peer-to-peer information among various types of network devices, such as fixed, portable, and mobile nodes. The use of these networks has increased dramatically, and they’re being used for implementing solutions for business, entertainment, and safety applications in business, residential, and industrial areas. The key characteristic of a mobile ad-hoc network is the ability of any mobile node to route traffic for other nodes in the network.
The concept of ad-hoc networking opens a broad spectrum of potential applications. The first, and the most important scenario, is the ability to establish a network in places where it’s not possible otherwise: i.e., in a disaster relief setting, or in a situation where the entire communication structure has been destroyed.
One thing we should be clear about is, there’s no doubt two machines in an ad-hoc network could be networked, but with a completely different art of network formation. No router, no administrator, no access server, etc. What does it mean? It means we can’t use the existing strategies for network control as efficiently as we do in a fixed wireless network. New technology requires new techniques. This is one of the major issues that appears to be an obstacle in deploying an ad-hoc network as a leading technology in the future wireless generation.
Routing, security, limited bandwidth, and low power are some of the important challenges to the technology. As far as low power is concerned, it’s more of a hardware issue. However, it does effect the other operations of the ad-hoc network. When each participating host has to be a router, packets are forwarded to all other nodes in the network. For wireless 1 to send packets to wireless 4, it has to take routing services from wireless 2. But what if wireless 2 refuses or is unable to do so. That’s a problem.
If we were to ask someone their basic motive in establishing a network, a typical answer might be "to ease communication" among various parties. So, for the time being we’ll limit our discussion to the routing mechanism in a mobile ad-hoc network.
As no router is available, each node has to rely on the others to route packets from one host to another. Possible problems could be that a node is not awake, or low on power. What if the node is busy fulfilling the other requests? What if there are already too many packets involved? What if the network is large? What if the node has changed location? Many more questions arise when we talk about routing mechanisms in mobile ad-hoc networks.
A number of solutions have already been proposed for routing in a mobile ad-hoc network. Some focus on maintaining a continuous network view, and some on establishing routes only when required. Both techniques have resolved problems up to a point, but they don’t provide the complete solution to the problem.
As for the first solution, maintaining network status all the time reduces the battery life of the participating nodes, and chances are the network won’t last long. And with the second, too many query packets not only could lead us toward a bottleneck, but would also consume a good amount of available bandwidth.
One of the possible solutions to the various problems in a mobile ad-hoc network is to recognize one problem as a central issue, and the rest of the problems as inter-related to the central problem. Based on the basic motivation of establishing a communication network, I personally regard routing as one of the core issues. If we take this approach, I’m quite sure we could come up not only with the solution to one problem, but with the solution to many other problems as well. This solution will hopefully lead us toward a structured form of a non-structured network.
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