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Ad hoc Networking
Mind-boggling Potential
Considering the nature of these networks, military applications come naturally to mind. But as of now, defense forces use satellite communications extensively. What is the real benefit they can derive from this emerging technology? "Indeed, the military uses satellite networks for a lot of their communication needs. But the bandwidth that is available over satellite channels is usually inadequate to satisfy the communication needs. Ad hoc networks are extremely useful when the nodes are localized (within a few kms or tens of kms of each other) and have to communicate with each other. Then they can get higher data rates with lower delays," says Basu, adding: "Also, satellite signals are often inaccessible indoors and in dense foliage. Needless to say, access to a satellite communication link often costs several dollars per minute whereas ad hoc wireless links are free."
"The MAC and routing problems are what make ad hoc networking very different from traditional wired IP networking or even wireless cellular or Wi-Fi networks," emphasizes Basu. According to him, in an ad hoc network, the MAC layer has to coordinate the order in which different nodes transmit in a distributed manner because there is no luxury of a central authority like the base station for computing the transmission schedule. The routing layer too has a more difficult task. Whereas in wired IP networks, hierarchical routing is feasible because nodes have static IP addresses which can be aggregated into hierarchical sub-network addresses. This is not possible in mobile ad hoc networks since nodes could be moving around. One mechanism of computing routes is by periodically broadcasting the status of all current neighboring links to all other nodes in the network. "A lot of research has been carried out in the last decade for optimizing this process since the wireless channel is much more resource-limited than a wired network. Recently, people have been rethinking even the design of physical layers to benefit ad hoc networking (eg, techniques such as cooperative diversity)," he says.
Ad hoc networks can play a major role in our day-to-day business. For instance, Basu talks about networking parking meters that could be configured through an ad hoc network. "One could have a transmitter on each parking meter; then you add a sensor that can tell whether there is a car in that spot. Thus, if a user wants a parking slot near his building all he does is query on the console in his car. The query is sent to the nearest parking meter, and if it isn't empty, the request would be forwarded to the next meter till it finds a free spot, and then even reserve it, if possible," he says.
Buildings could also be networked on such sensorized mesh ad hoc networks, he says. "If it is a bit chilly, the sensors in different windows transmit a message, and they are closed automatically, thereby saving heat," adds Basu.
"Blue tooth is the first true ad hoc product. It can support up to 80 nodes, sadly till date it has only been used for cable or wire replacement. It is a cool application, so is Zigbee," he says.
Battery life is one of the biggest challenges faced by the industry. "Since the devices are constantly transmitting data, the battery life could be a big issue. For that one needs to develop better protocols, or dramatic gains in the battery technology is required," Basu adds.
In the years to come, Basu hopes to see a lot more ad hoc networks, even in India. "The potentiality of ad hoc networks is mind boggling-from saving lives, in case of natural disasters like the tsunami or an earthquake, to making our lives easier and more happier. The future could be quite like the science fiction movies that we often watch. We are getting closer to that future with ad hoc networks," signs off an optimistic Basu.
Source: Dataquest
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