Feature: Networking the ‘ad hoc’ way - TR35 2

Here goes the second part of the 6 series on TR35 Winner. This time I talk about ad hoc networks , believe me it was one tough nut to crack. I earnestly thank Prithwish in helping me understand ad hoc in around an hour that we spoke. Check the article for yourself.


Networking the ‘ad hoc’ way

Ad hoc networks are the current talk of the town with scores of companies working on the standards and applications. Pritwish Basu a scientist at BBN Technologies has won an award for his work on ad hoc networks.

Boxing day (December 26) of 2004 will be forever be etched in our memories. It was the day, when human misery hit a crescendo, a day when nature unleashed its fury on the South Asian shores of Indonesia, India, Srilanka and others. It was the day when the Tsunami stuck. While innumerable people died in the wake of the flooding waters, thousands died in the aftermath, for want of medicine and food.

There was no real paucity of medicine and food packages, what was lacking was a communication structure over which the relief process could be coordinated. But how can relief agencies communicate, when the whole infrastructure has been ripped apart? Satellite communication is quite dear (cost wise) and often unreliable in cases of far-flung locations.

An alumnus from Indian Institute of Technology (Delhi), based in the U.S., is currently working on a technology that will make all such concerns (communications without infrastructure) redundant. And, he recently received a prestigious award for his work. Pritwish Basu a scientist at BBN Technologies has developed algorithms that enable wireless devices to interconnect with each other (ad hoc networks) with very low drop rates. For his work, Basu recently awarded the prestigious TR35 Award. It is an award given annually by MIT’s Technology Review to a selection of 35 of the world’s leading high-tech innovators under the age of 35.

Thirty-one year old Basu is pretty gung-ho on being selected for this award and terms it to be a ‘pleasant surprise’. He describes ad hoc networks as wireless networks that can be set up quickly for communication between nodes and do not need any infrastructural support from satellites, cellular towers or base stations.

Ad hoc is a term borrowed from Latin and can be loosely translated as, “for this purpose only”. The term aptly describes the way the whole network is configured. Unlike a traditional network, in which, all the devices are linked to a central hub, in an ad hoc network, all the devices communicate with each other and relay data forward.

It may seem fairly similar to the Wi-Fi network that is common nowadays. Basu clarifies. “The similarity with Wi-Fi (IEEE 802.11a/b/g) or WiMax is that an ad hoc network also may use similar wireless radio transceivers. However the difference is that in the case of Wi-Fi etc., there is a static base station that is established a priori and that allows wireless nodes to access the Internet; in case of ad hoc networks, there is no base station and nodes communicate directly with other nodes in their transmission (radio) range, and they can help in cooperatively forwarding packets to remote nodes that are not in direct communication range of the source node. There are several well-known ad hoc routing protocols that can perform this task,” he says.

In a way, Game theory finally makes an appearance in the ICT domain. For the past few decades, Game theory has been used as a tool for understanding the way people, communities, or nations interact with each other. Basically speaking, Game theory talks about interplay of different people, wherein each desires to maximize his benefit. All these people cooperate to a level, till such state is reached (maximum benefits for all). This is cooperation at its best. Ad hoc networks symbolize cooperation, wherein one device collaborates with another for transmitting data.

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 of all soldiers in the armed forces. 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.”

“Ad hoc networking has forced designers to rethink different layers of the network protocol stack above the physical layer, i.e., medium access control (MAC), network (routing), transport, and application layers. 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 and hence it is not as easy to aggregate their addresses into subnet addresses. 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 occurred 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 (e.g., techniques such as cooperative diversity),” he says.

Amazingly, ad hoc networks can play a major role in our everyday lives. For instance, Basu talks about networking parking meters that could be configured through an ad-hoc network. “One could have a transmitters 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 to 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 reserves 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 truly 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 says.
Ironically, for a man who is at the forefront of designing new networks, could have been a doctor as he had passed a few medical entrance exams. But his love for maths scored over his interests in medicine. “I do not regret that choice,” he says. His father is a retired civil servant and mother a housewife, both currently reside in Delhi. Basu considers Boston University to be his Alma meter, where he did his MS and PhD. He has also graduated from his love for cricket to soccer and baseball and continues to visit India regularly.

In the years to come, Basu hopes to see a lot more ad hoc networks, even in India. “The potential of ad hoc networks is mind boggling. From saving lives in case of natural disasters like tsunami or earthquake, to making our lives easier and more happier. The future could be quite like the science fiction movies that we often see. We are getting closer to that future with ad hoc networks,” signs off an optimistic Basu.

India is regarded as an IT Powerhouse, do you think, there is enough innovation happening out of India?
There is innovation happening in India in institutions like IISc but I don’t think that it is enough considering how much progress India has made in the IT sector recently. I believe this is primarily due to the lack of research funding from the Indian IT industry. The government funding is inadequate as well. There is a direct relationship between R&D funding and research/innovation output. I believe if the IT sector invests some of its profits towards fundamental and applied research (and not just proven products), then we will see several innovations happen in India. The other roadblock is the highly structured educational system in most schools and colleges. There is much more emphasis on consistency over all subjects rather than creativity or innovation.

Can ad-hoc networks make an appearance in India?
Mesh networks and sensor networks are forms of ad hoc networks that could easily make an appearance in India. Asset tracking and monitoring applications could motivate the use of sensor networks in India. The deployment challenges and business models may be slightly different though.

Shashwat DC

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