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What are ad hoc networks? And how did you come to use the term for it?
Ad hoc networks are wireless networks that can be set up quickly for communication between nodes and which do not need any infrastructural support from satellites, cellular towers or base stations. The term packet radio network was a precursor to the term mobile ad hoc network or MANET. The latter has been in vogue since the mid-90s. I started working in this area around 1999 – the term was already popular in the research community by then.
How is the technology different from the ones that are currently quite popular like WiMax or Wi-Fi?
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.
 You have spoken about, how the military can make use of these networks. But are they not already using satellite networks for communication. What are the benefits they can derive from it?
Yes, the military indeed 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.
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.
How does ad hoc technology work? How does the radio waves compare to IP network?
Ad hoc networking has forced designers to rethink different layers of the network protocol stack above the physical layer, i.e., medium access (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.
In ad hoc networks, 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. 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).
What are the different devices that can make use of ad hoc? What are the data transfer rates?
All devices that are equipped with appropriate radio hardware can run an ad hoc network protocol stack and they can form an ad hoc network. The most well known examples of ad hoc networking hardware in the commercial world include Wi-Fi cards configured in “ad hoc mode” (as opposed to “infrastructure mode”), Bluetooth, and Zigbee transceivers. The raw data rates of various 802.11 cards (a/b/g) are in the range of a few tens of Mbit/s (11-54 Mbps) although the aggregate achievable network throughput is typically much lower than that and it diminishes with the addition of new nodes to the network.
Your association with BBN Laboratories and your work there?
I have been working at BBN Technologies since 2003. We are an advanced R&D consulting firm based in Cambridge (Massachusetts, USA). Among many “firsts”, BBN’s biggest claim to fame is that they built the first ARPANET routers in early 70s. (The ARPANET was the precursor to the Internet.) I work on various research projects in mobile ad hoc networks, low energy sensor networks, and disruption tolerant networks.
India is regarded as an IT Powerhouse, do you think, there is enough innovation happening out of India? What are the reasons for it or the lack of it?
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 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.
How do you unwind? What are you interests? Do you visit India?
I am a sports fanatic and follow baseball and American football religiously. I used to watch cricket and soccer a lot when I was in India but those are rarely shown on US television; hence I was forced to migrate to following new sports. I play soccer, chess, and hike occasionally. I am also a movie buff – especially like watching good independent films, and I dabble in photography. I visit my parents and family in India about once a year. If I’m on a trip to Europe, I try to extend it into a bonus trip to India.
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