Alumni @ IITD

IIT Delhi alumnus Professor Emeritus, Stanford University Arogyaswami Paulraj has been inducted into the National Inventors Hall of Fame for developing wireless technology to transmit and receive data at high speeds. Professor Paulraj pioneered MIMO a wireless technology that has revolutionized broadband wireless internet access for billions of people worldwide. MIMO improves both transmission data rates and expands network coverage. It is the essential foundation for all current (WiFi and 4G mobile) and future broadband wireless communications. Born in Pollachi, Tamil Nadu, India, Prof Paulraj joined the Indian Navy at age 15. The Navy, impressed with his academic record, sent him to IIT Delhi, where he earned a Ph.D. for advances to signal filtering theory.

He will be formally inducted at the 46th Annual National Inventors Hall of Fame Ceremony on May 3, 2018, at the National Building Museum in Washington, D.C.

In an interview with Dr Vanita Srivastava, Prof Paulraj talks about MIMO, his stay in IIT Delhi and more. Edited excerpts.

You have been inducted to the National Inventors Hall of Fame for developing wireless technology to transmit and receive data at high speeds. Can you please elaborate a little bit on the MIMO technology.


MIMO (multiple-input multiple-output) wireless uses multiple antennas both at the transmitter and the receiver to enable a technique called Spatial Multiplexing which boosts data rates in a wireless link. MIMO does this by creating "parallel spatial data streams" within the same radio frequency channel. MIMO requires special encoding of signals at the transmitter and corresponding decoding of signals at the receiver. The key idea in MIMO is that a signal transmitted from each antenna of the transmitter antenna array, given the right propagation conditions, can appear with a different spatial signature at the receiving antenna array, and thereby allows the receiver to separate the different impinging transmit data streams, enabling spatial multiplexing.

MIMO effectively multiplies the radio spectrum, a scarce and very expensive resource, by the number of antennas used at both ends. Current wireless systems like WiFi and LTE support MIMO with up to 8 antennas. Future systems like 5G cellular technology are predicted to employ 100+ antenna configurations, offering a huge multiplication of the radio spectrum.


Can you please tell a little about your stay in IIT Delhi? What was your PhD research focused on at IIT Delhi


In July 1969, then a Lieutenant in the Navy, I was fortunate to be deputed to IIT Delhi for two years for an M.Tech program. I had joined the Navy as cadet via the National Defense Academy in 1961 and after stints with a variety of training schools and some sea service; I was delighted to finally arrive at a real university. I was lucky to quickly catch the eye of Profs. Indiresan and Duttaroy, who encouraged me to sit for the Ph.D. entrance exam, which I presumably cleared. Prof Indiresan, then Head of EE Dept., had great difficulty in persuading the Navy and the IIT Senate to allow me to switch to a PhD program. The Navy relented on the condition that I finish my PhD work in my originally allocated two year deputation period. I therefore returned to the Navy in June 1971, with some core research in non-linear estimation theory already done, but had yet to write my thesis. To my great surprise I was back at IITD in mid-1972 for 18 months to undertake a sonar design project. This work was very different from my theoretical PhD research, but perhaps even more exciting.

My Ph D work used stochastic calculus and advanced math. It unified a whole range of results in that area. The thesis resulted in an invite form Stanford University to teach a course on that subject, but because of my Navy status, I could not get GOI permission.


What steps should be taken to reverse the brain drain in India?


My hope is that brain drain is slowing a lot. That's good news. We still have to build companies in core technology in computing and communications. I hope India will do that now and not be 100% dependent on imports.


What do you like to do in your spare time?


Play with my grandkids - Anjali, Arman, Indira and Amara.