It was March 1960. A young, enthusiastic, and academically brilliant boy sat for the NDA exam and qualified. Though he didn’t fancy a career in defence services, he joined the academy in early 1961.
For someone with an academic bent to be enrolled at an institution where the focus was on sports, horse riding, gymnastics, and drills was unusual. Even his instructors at the academy would often tell him that he had made a wrong choice.
But it was too late to back out. Moreover, there was no alternative that he could think of.
That’s how Arogyaswami J Paulraj became “a navy officer by chance”.
Many years later, he would go to IIT Delhi for higher studies, and get exposed to the world of science, mathematics, and technology, eventually becoming “a scientist by choice”.
That puts him in a unique position — a brilliant scientist familiar to many in defence-services circles, and to some in the telecom industry, given his prodigious inventions.
Even though the world uses one of his inventions every day, Paulraj remains a face in the crowd for many.
A proud Indian at heart, the highly decorated former commodore of the Indian Navy has a string of accolades to his credit — the Padma Bhushan; two top honours in the telecommunications industry, the Marconi Prize and IEEE Alexander Graham Bell Medal; and a member of the USPTO’s National Inventors Hall of Fame. Yet, the professor emeritus of Stanford University’s Department of Electrical Engineering is one of the humblest souls one would come across.
If you are reading this on a smartphone using a 4G/LTE or 5G network, or on a laptop using a Wi-Fi network, you are using one of his greatest inventions that changed the way we communicate and remain connected. Paulraj is the inventor of “multiple input, multiple output” technology, or MIMO, without which today’s 4G, 5G, and Wi-Fi networks would not have been possible.
But, the road to MIMO’s invention was anything but linear. On one plane, Paulraj’s story is that of a small-town boy’s rise to the global stage via two disparate institutions — the Indian Navy and Stanford University. On another, it’s a journey in which serendipity complemented an urge to challenge the frontiers of technology. Here’s the tale, with its several twists and turns.
Calculus, Sputnik-1, and Russian kidnappers
Born on April 14, 1944, in Pollachi, a small town near Coimbatore in Tamil Nadu, Paul (as he is commonly known) is one of the six siblings. His father, Sinappan Arogyaswami, joined the Indian Navy soon after Paul’s birth. Paul did his early schooling in Mumbai, Coimbatore, and Cochin.
He completed his high school at the age of 15 from a boarding school called Montfort in Yercaud. Paul was a top-ranking student with a keen interest in Maths and Physics. When he came across Calculus, it caught his imagination. But, Calculus was not taught in schools back then, so he started exploring the subject on his own.
It won’t be wrong to say that this was the time the foundation of a genius started getting built.
Retired colonel Arul Raj, Paul’s younger brother, says, ”Paul was a genius since childhood, and I was more a playful child and not academically that bright.” When his father used to point this out to him, Arul would jokingly say, “All the brain went to my elder brother.”
Paul’s academic excellence had put him in funny situations at times. In 1957, when he was in high school, the Soviets launched the first Sputnik. Around that time, some Russians came to visit Yercaud. There were rumours in the school that they had come to kidnap Paul to work on their space programme because of his talent. The incident still brings a broad smile to his face.
A PhD with a twist
In 1959, after finishing high school, Paul joined a pre-university course at Loyola College in Chennai. He always fancied a career in Maths and Physics. But lack of guidance, coupled with limited financial resources, ultimately led him to join the National Defence Academy (NDA), which was completely free, given his father’s navy background.
Defence services was not the career he wanted, given his academic interests. Even the NDA faculty would tell him that he was in the wrong place. Nonetheless, he graduated at the top of his batch, bagging the president’s gold medal and achieving the position of academy cadet captain.
But his knack for science and technology stayed alive. In 1964, he joined the Naval College of Engineering at Lonavala and opted for the Electrical Engineering branch. While this professional training programme wouldn’t earn him a BE degree, he was the top student during the five years he spent at the institute.
It didn’t take long for the navy officials to figure out Paul’s academic genius. Although the lack of a formal BE degree made him ineligible for enrolment in a higher engineering course, the navy nominated him for the ME course at IIT Delhi. Professor PV Indiresan, who later became Paul’s mentor, impressed with his academic excellence, convinced the IIT Delhi senate to waive the requirement of a BE degree.
According to Paul, he was probably the first officer from the navy to get such an exemption. Later, the government decreed that the professional training received by former NDA officers was equivalent to a BE degree. Many bright navy officers benefitted from this move, which redefined the course of the Indian Navy.
But destiny had other plans for Paul.
Indiresan soon figured out that Paul’s aptitude was way above the ME curriculum. He suggested transferring Paul to a PhD programme. But, the big hurdle was to convince the higher-ups in the navy.
He wrote to the then vice-chief of naval staff, vice-admiral Krishnan to allow Paul to shift to a PhD programme instead of an ME. “The navy does not need scientists,” the vice-admiral wrote on the file, rejecting the proposal.
However, after a lot of persuasion, the navy relented on the condition that Paul would be given only two years — the duration of the ME course — to finish his research work. By the time Indiresan got all the approvals, only 18 months were left for the research work, but in yet another show of brilliance, Paul completed it within that time frame. Under normal circumstances, it would have taken at least four years to complete a PhD.
Years later, Paul’s wife Nirmala remembers meeting some of his IIT Delhi professors. “We used to hide from this guy [Paul] because he would have read two chapters ahead of what we were teaching. We used to keep our fingers crossed that he doesn’t start asking questions,” they told her.
At IIT Delhi, Paul had the opportunity to meet professor Thomas Kailath, another mentor and later a colleague at Stanford University, who visited the campus to teach filtering theory, which eventually became Paul’s research area. Kailath was so impressed by Paul’s thesis on non-linear and linear filtering that he invited him to Stanford University to deliver lectures.
The PhD flagged off Paul’s amazing and diverse achievements in the field.
A submarine attack opens up new horizons
As they say, things happen for a reason. Joining the Indian Navy had turned out to be a boon in disguise for Paul.
After finishing his PhD research, Paul returned to the navy in 1971. His thesis work was still pending, and he wanted to stay at IIT Delhi for another year to finish it, but the navy was planning a sea duty for him. On Paul’s request, the navy agreed and posted him at Navy Headquarters in Delhi. He had a busy routine — a day job at the Navy Headquarters and nights at the IIT Delhi library writing his thesis.
But destiny had other plans.
In December 1971, the Indo-Pak war broke out. The Indian Navy frigate, INS Khukri, fitted with a prototype of the Sonar 170B modified by Bhabha Atomic Research Centre (BARC), was on a combat-patrol mission when it was sunk in a torpedo action. The sonar was unable to detect the enemy submarine and India lost over 200 brave soldiers, many of whom Paul knew.
In an official navy history record, Paul reminisces that the morning after the sinking of INS Khukri, commodore Chatterjee, who was director of the electrical engineering department at Navy Headquarters, asked him if he knew anything about Sonars. “I don't remember what I told him, but later that afternoon, I accompanied him to Bombay,” Paul recalls.
Chatterjee recommended Paul to lead the Sonar 170B project to improve its performance. Paul noticed some shortcomings in BARC’s approach and proposed to develop an alternative receiver technology using advanced signal processing. The navy also agreed to his request to allow him to work on the project at IIT Delhi.
After some initial hiccups, Paul and his team developed a new technology for Sonar 170B within three months. After extensive trials, the navy approved the new model for deployment in its fleet. Alongside, Paul finished writing his PhD thesis and submitted it around the middle of 1973.
In 1974, Paul received the Vishisht Seva Medal for “distinguished service of a high order” for successfully leading the project to improve the performance of sonar 170B.
A specialist in anti-submarine warfare, the former chief of naval staff, retired admiral Vishnu Bhagwat, collaborated with Paul on sonar-technology development.
He vividly remembers that when he requested Paul to fund higher studies of a couple of brilliant navy officers several years later, he immediately agreed. “I wanted to build an army of mini-Paulrajs across the Indian Navy,” he says.
Admiral Bhagwat is well-known for his support for greater indigenisation of the Indian Navy’s technology base. Emphasising the importance of having in-house technology experts, he adds, “If the opponent is technologically so ahead that you can’t take it on, that’s a threat.”
On his part, Paul says, “I admire and share admiral Bhagwat’s lifelong quest for greater and authentic indigenisation of the Indian Navy’s technology base.”
APSOH: inexperienced team, limited resources, so what?
After the sonar project, Paul went for a research fellowship programme on signal-processing algorithms at Loughborough University, UK, in 1974. The navy used to send Paul on many such programmes when he was not involved in any major project. ”When they didn’t know what to do with him, they sent him off,” says Nirmala Paulraj jokingly.
Paul spent a year and a half at Loughborough University and on orders from the Naval Headquarters, he visited some sonar manufacturers in the UK and France at the end of the programme to assess the design and performance of the new panoramic sonars.
On his return, Paul approached senior navy officers with a proposal to develop indigenous next-generation panoramic fleet sonar. Initially, the navy was reluctant, but given the remarkable success of the Sonar 170B project, he was given the green signal. This time, the project was much bigger and more complex.
The navy assigned Paul to DRDO’s Naval Physical and Oceanographic Lab (NPOL) in Cochin in 1976 to lead the development of this new sonar. The project was codenamed APSOH (advanced panoramic sonar hull-mounted).
At first, NPOL didn’t involve Paul in the panoramic sonar project it was already working on. Paul recalls that the poor history of relations between service officers and the R&D community could have been the reason for this.
NPOL had ordered a computer from the US, and it arrived damaged. While at Loughborough University, Paul built a minicomputer by himself and wrote an assembly code for its operating system. He wrote a new boot code for the damaged computer and fixed it. This did the trick, and he was involved in the sonar-project team, which he eventually led and delivered successfully. The project took seven years to complete.
According to Paul, APSOH was the biggest military electronics project in India at that time and one of the biggest indigenous technology commitments from Indian defence services. Improved variations of APSOH are still deployed in the navy’s warships.
In the official navy history, Paul recorded his thoughts on APSOH in retrospect: “Now that I lead aspects of wireless technology at a worldwide level, I have a better understanding of the technology development process in the developed countries. I sometimes compare APSOH with other achievements I see in my new field. I am always amazed as to how such an inexperienced team, with such few resources, pulled off this major project in such a short period. APSOH was an impossible dream that came true for many of us.”
In 1984, Paul received Ati Vishisht Seva Medal for “distinguished service of an exceptional order” for the development and commissioning of APSOH.
Undying ESPRIT
After the APSOH project was completed, the navy rewarded Paul with a two-year fully sponsored sabbatical anywhere in the world to explore new areas. Paul requested professor Kailath to let him join his group at Stanford University. Initially, Kailath declined, saying that he may not be a good fit, as he was more of a practical engineer, and his group worked more on theoretical concepts. But later, on Paul’s persistence, he allowed him to join as visiting faculty. In 1983, Paul moved to Stanford along with his family.
Kailath’s group was working on the estimation of direction-of-arrival (DOA) of multiple signals using antenna arrays. Paul had worked on DOA estimation of a single signal during the APSOH project. The problem at Stanford involved multiple signals, and Paul developed a new approach to solve the DOA problem through an algorithm called ESPRIT (Estimation of Signal Parameters via Rotational Invariance Technique). His hands-on experience of working on sonar projects, combined with an advanced mathematical approach, resulted in a revolutionary solution.
ESPRIT is a topic still taught in universities. Professor Helmut Bolcskei, chair of the Mathematical Information Sciences at ETH, Zurich, says, “ESPRIT is not often mentioned, but it’s a famous invention. I still teach it to my students. It is such an elegant algorithm.”
In 1986, Paul returned to India and founded the Centre for Artificial Intelligence and Robotics in Bengaluru. Briefly thereafter, DRDO proposed his name to lead India’s ambitious light combat aircraft (LCA) project. But, given his past experience with bureaucratic bottlenecks, Paul proposed a different operating structure for the efficient management of the LCA project, which was eventually stalled.
He was later deputed as chief scientist at Bharat Electronics (BEL), where he started two central research labs. During this time, he also built another lab, the Centre for Development of Advanced Computing, in Bengaluru.
That was when Paul started to think about moving to an academic career. But changing course at the age of 46 and his service background posed challenges.
Hinting at how politics within organisations and bureaucracy impacted him, Nirmala Paulraj says, “Stress was never from work. Stress was always from people causing problems.”
Retired admiral RH Tahiliani, former chief of the naval staff in one of the official navy histories, has shared his disappointment with the circumstances that led to Paul’s decision to move to the US: “His departure for Stanford University was a major loss for our country and the circumstances that led to his move may explain why we have so few Nobel laureates from India.”
MIMO’s link with rain and a haircut
In 1991, Paul took early retirement from the navy and approached Kailath again for a post-doc position at Stanford. Kailath offered him a research associate position at Stanford for the interim.
While many were disappointed about him leaving the country, Paul, with his characteristic optimism, always looked at the positives. At the Marconi Prize event, he said, “Coming to Stanford was one of the most fortunate breaks in my life. I am very grateful for the opportunity.”
At Stanford, renowned math professor Gene Golub was working on a project for the US Air Force to intercept and separate interfering signals arriving from different directions. He involved Paul in this project.
Paul built a prototype to analyse and understand the signals in the real world instead of using software-based simulators. Using cordless phones as different signal sources and a base station with multiple antennas to receive signals, he experimented with a range of signal-separating algorithms. The system was able to parse the signals effectively when the phones were far apart, but failed when they were too close.
And then it started raining.
The team moved the set-up indoors and to its surprise, the system was capable of separating the signals even when the phones were just next to each other. Paul started to think of the logical explanation behind this. It didn’t take him long to figure out that it was the multiple-path propagation of signals that bounced from the walls and arrived at a different angle at the base station (despite the phones being next to each other) that helped the receiver separate them. Though this finding didn’t help in cracking the US Air Force problem, it planted the seed for the invention of MIMO.
One day, as he was thinking about this interesting finding while having a haircut, a Eureka moment happened: What if he put two antennas on the transmitter and use two antennas on the receiver side and send two data streams on the same frequency channel? Wouldn’t the data rate be doubled?
Thus, MIMO was born.
Recalling the incident in one of his interviews, Paul, with characteristic humility, said, “It was rain and some good fortune that led to MIMO’s invention.”
Later, he did some mathematical calculations and figured out that by having multiple antennas (say, n) on each side of the radio link, the capacity of the link could be increased n times without any additional power.
Although companies and investors back then were sceptical about the idea, Paul would go on to have the last laugh and successfully demonstrated MIMO’s feasibility when he founded his first company Iospan Wireless.
Paul explains MIMO thus: “MIMO multiplied the link speed of wireless networks manifold and also improved their range and reliability. MIMO’s speed-up is 4x in most current deployments, with options for 8x. Today’s pervasive 4G-5G mobile and Wi-Fi networks would be impossible without MIMO.”
MIMO-powered wireless networks enable 6.5 billion smartphone users to access the Internet, as well as connect billions of IoT devices. Industry groups estimate the global economic value of wireless networks in 2021 to be around USD7.8 trillion.
“MIMO was a gamechanger for wireless communications. It was what enabled high-speed, high-reliability wireless communications, not only in cellular but also in Wi-Fi,” says Andrea Goldsmith, dean at the School of Engineering and Applied Science at Princeton University, US.
Goldsmith is among the most influential electrical engineering professors in the US. She serves on many of the nation’s advisory positions, including the Presidential Committee on Science and Technology, and is on the board of several companies, including Intel, Medtronic, and Crown Castle. She and Paul were colleagues at Stanford for more than two decades.
It was September 6, 1994, exactly 29 years ago, when the United States Patent and Trademark Office granted the patent for MIMO’s invention to Paul, with Thomas Kailath as co-inventor.
A rare combination
While Paul’s strength in theoretical aspects was nurtured by his mentor, professor Kailath, at Stanford University, his inclination towards developing solutions and applications comes from professor Indiresan, his mentor at IIT Delhi.
Admiral Bhagwat aptly captures this unique combination when he says, “He has this unique ability to carry a concept into mathematical formulations, and then convert it into an experimental project, and convert that project with the technology and the materials available to have the best-in-class product.”
Soundararajan echoes the thought, “He is that rare genius who is not only a scientist, but a visionary and a leader in the true sense of the term.”
Professor Bolcskei of ETH, Zurich, agrees. “He’s an absolutely impressive systems engineer. He combines that with a deep mastery of physics and mathematics. These three things together make him a singular figure … which for a scientist is very rare. That singles him out.”
Bolcskei, well known for his contributions to the theory of MIMO communications and deep neural networks, was a post-doctoral researcher with Paul’s group at Stanford in the late 1990s. “I have watched with pride his contributions at the highest levels to the theoretical foundations of signal processing,” says Paul about Bolcskei.
Bolcskei says he tries to adopt Paul’s constructive mindset — one that is only interested in substance. “If something goes wrong, he will just say, ‘How can we move forward?’ There will never be a clean-up, or trying to know who was responsible. He cares about people. He understands that people are who they are, and we all make mistakes.”
The sentiment is echoed by Aruna Soundararajan, former telecom secretary, Department of Telecom, and chairperson of the Digital Communications Commission. “For him, only the cause matters. He doesn’t look at personalities, he doesn’t look at personal setbacks. He is like Arjuna, who only sees his target,” she says.
“The IAS cadre has produced several outstanding officers, but Aruna Soundararajan stands out even within this elite club. Her intelligence, dedication, and judgement while leading tech-heavy departments have served India very well,” Paul says about her capabilities.
For Paul, it is the collective, and not the individual, that matters. It’s never about him. “He's incredibly humble. He’s also incredibly generous. He spends a lot of his time promoting other people, promoting students, and promoting colleagues.” says Goldsmith. “As a scientist, what differentiates him is his vision and depth of knowledge. There are very few people that span such a broad range of experiences.”
At the felicitation ceremony of the Marconi Prize, professor John Cioffi, the inventor of DSL technology and a colleague of Paul at Stanford, said, “Paul’s technical capability is almost unparalleled. Such people are pretty rare.”
Nirmala Paulraj puts across Paul’s brilliance in a different way, “I used to be a quiz champion. But now, I don’t even Google, I just ask Paulraj and the answer is there. My Google is Paulraj.”
Given all the interactions I have had with Paul, I can say with certainty that he has an aura that none can miss.
Honours and accolades
In all, 265 patents are registered with the US Patent and Trademark Office that have Paul’s name as the inventor or co-inventor. Besides, he has won a host of awards in India and abroad.
While the list is long, here are some of the most prestigious awards and honours that he has received:
- National Inventors Hall of Fame, 2018: Paul was inducted into the US Patent and Trademark Office National Inventors Hall of Fame for the invention of MIMO. Over the past 50 years, 624 scientists have made it to the list. They include Thomas Alva Edison, Guglielmo Marconi, Alexander Graham Bell, Claude Shannon, Nikola Tesla, the Wright Brothers, and Steve Jobs.
- Marconi Fellow, 2014: Again, the invention of MIMO fetched Paul this award, considered the Nobel Prize equivalent for technology pioneers. There are 56 Marconi fellows globally, including Martin Cooper, for inventing the handheld mobile phone; Vinton G Cerf, and Robert Kahn, known as fathers of the Internet, for designing TCP/IP protocols; Tim Berners-Lee, for inventing the World Wide Web; John Cioffi, for inventing DSL; professor Yash Pal, for applying modern communications technology to meet the needs of Indian villagers; and Lawrence Page and Sergey Brin for founding Google.
- IEEE Alexander Graham Bell Medal, 2011: Awarded for exceptional contribution to communications and networking sciences and engineering, Paul received this prize for the application of MIMO in wireless communication systems. There are 55 recipients of this award globally.
- Padma Bhushan, 2010: Paul received India’s third-highest national award for his contributions to the Indian Navy.
“In telecom, there are two top recognitions — the IEEE Alexander Graham Bell Medal, which has a bias towards theoretical contributions, and the Marconi Prize, which honours contributions that convert breakthrough ideas into products benefiting billions of people. I am incredibly honoured to have won both,” Paul said during his address at the Marconi Prize felicitation event.
Then President of India, Pratibha Patil presents the Padma Bhushan to Prof. Arogyaswami Joseph Paulraj in New Delhi on March 31, 2010.
The family man
While juggling between the sonar 170B project and completing his PhD thesis, Paul got married in February 1973 to Nirmala. Earlier this year, they celebrated their 50 years of togetherness. According to Paul, his wife has always been his biggest support. “It has been 50 years of married life and Nimi has persevered in supporting the family through life’s inevitable challenges,” says Paul.
They are blessed with two daughters. Mallika, who is into environmental sciences, graduated from Stanford and later studied at LSE, London. Nirupa, who studied medicine at Manipal, and is a physician in Las Vegas.
Paul always wanted both his daughters to explore technical careers and study at Stanford, but now his only hope is from the grandchildren, who Nirmala Paulraj says hide whenever he brings up this discussion.
Nirmala Paulraj says senior officers from the armed services would often tell her, “You have to be the one to make the sacrifice to allow him to achieve his potential.” Now, with great pride, she says, “I feel I have done that.”
Though on a lighter note, Nirmala says, “Behind every successful man, there is a disgruntled wife.” But given the way things have worked out for Paul, she adds that she is very happy and proud to be the disgruntled one.
Commenting about his reserved nature, his brother, colonel Arul Raj, says, “When we all get together, we crack jokes and pull each other’s leg. He is quiet and more philosophical. But that is his nature.”
Arul is India’s foremost military painter. His war paintings adorn many iconic locations – the Rashtrapati Bhawan, Service Headquarters, and military museums and offices. The new National War Memorial in Delhi has six large bas-relief bronze murals of war scenes, which all are based on his paintings.
Commending the legendary talents of his younger brother, Paul says, “He is the pride of our family. And we all love him.”
His heart still beats for India
“I’m not ready to stop work yet. My biggest challenge is finding time for all the things I want to do,” Paul said when he received the Marconi Prize in 2014. About a decade later, he still feels the same.
About to be an octogenarian in a few months, Paul continues to work for the betterment of India. ”I wish I was younger because there is so much to do.”
Commenting on Paul’s love for his country of origin, admiral Bhagwat says, “He is a patriot of high order … a national treasure.”
Paul has articulated an ambitious vision for India and shared it with the Indian government at the prime-ministerial level. He strongly believes that India has the potential and resources to build an ecosystem of world-class universities that will help brilliant scientists and engineers to stay in the country and innovate.
Colonel Arul Raj adds that Paul “has this great dream to see this country [India] come up”.
Paul was the chair of the steering committee of the High-Level Forum for 5G in India, which played an instrumental role in the country’s 5G journey.
He is also on the advisory committee of India Semiconductor Mission, chairing the Fabless Chip Design segment.
Paul identifies semiconductors, aerospace particularly commercial jets, new-molecule pharmaceuticals, advanced instrumentation, and biotechnology as the core areas on which India should focus. He strongly believes that academia, industry, and the government need to work together to make this happen. On this, Soundararajan says, “He knows exactly where each capability is available. He knows the strengths and weaknesses of Indian academia. He knows the strengths and weaknesses of Indian industry. He knows how our policy environment is structured.”
Paul is clued on to developments on the ground. He travels to India almost every other month. He interacts with professors, students, top industry executives, government officials, and policy makers. He wants the government to find ways to target just 5% of the global value chain. That, he says, will be enough to serve as the launchpad for further progress.
“My dream for India is to one day become a leader in innovation-driven advanced-technology industries,” says Paul. He wants it to be a nation with research universities that contribute to human advancement at the highest levels. “An India that rises to become an influential and respected nation – not just for its economic and technological progress, but also for its high values and the way it cares for the least of its citizens. A nation that is a beacon for peace, hope, and reconciliation for all humanity,” is how he sums up his vision.
To make this vision a reality, here’s his advice to the youth of the country: “Nothing worthwhile is ever easy. A worthwhile goal takes hard work, patience, and perseverance. Hard work comes more easily if we love what we do, and we usually acquire that if we are good at doing it. But finding what we are good at is also not easy. More likely, it comes from working hard at something worthwhile which slowly turns into the work we love. Once we find that, many things will fall into place.” He sums up by saying, ”Great people are just ordinary people with an extraordinary amount of determination.”
Paul is a living example of how hard work, perseverance, patience, and determination can lead one to the greatest heights. Given all the contributions that he has made to the country and to the world, it won’t be wrong to say that he is like an Einstein or Newton of today.
As the author of this profile, I feel honoured having met this living legend in person and it was an absolute pleasure to pen down his momentous contributions.
(Graphics by Sadhana Saxena)That puts him in a unique position — a brilliant scientist familiar to many in defence-services circles, and to some in the telecom industry, given his prodigious inventions.
Even though the world uses one of his inventions every day, Paulraj remains a face in the crowd for many.
A proud Indian at heart, the highly decorated former commodore of the Indian Navy has a string of accolades to his credit — the Padma Bhushan; two top honours in the telecommunications industry, the Marconi Prize and IEEE Alexander Graham Bell Medal; and a member of the USPTO’s National Inventors Hall of Fame. Yet, the professor emeritus of Stanford University’s Department of Electrical Engineering is one of the humblest souls one would come across.
If you are reading this on a smartphone using a 4G/LTE or 5G network, or on a laptop using a Wi-Fi network, you are using one of his greatest inventions that changed the way we communicate and remain connected. Paulraj is the inventor of “multiple input, multiple output” technology, or MIMO, without which today’s 4G, 5G, and Wi-Fi networks would not have been possible.
But, the road to MIMO’s invention was anything but linear. On one plane, Paulraj’s story is that of a small-town boy’s rise to the global stage via two disparate institutions — the Indian Navy and Stanford University. On another, it’s a journey in which serendipity complemented an urge to challenge the frontiers of technology. Here’s the tale, with its several twists and turns.
Calculus, Sputnik-1, and Russian kidnappers
Born on April 14, 1944, in Pollachi, a small town near Coimbatore in Tamil Nadu, Paul (as he is commonly known) is one of the six siblings. His father, Sinappan Arogyaswami, joined the Indian Navy soon after Paul’s birth. Paul did his early schooling in Mumbai, Coimbatore, and Cochin.
He completed his high school at the age of 15 from a boarding school called Montfort in Yercaud. Paul was a top-ranking student with a keen interest in Maths and Physics. When he came across Calculus, it caught his imagination. But, Calculus was not taught in schools back then, so he started exploring the subject on his own.
It won’t be wrong to say that this was the time the foundation of a genius started getting built.
Retired colonel Arul Raj, Paul’s younger brother, says, ”Paul was a genius since childhood, and I was more a playful child and not academically that bright.” When his father used to point this out to him, Arul would jokingly say, “All the brain went to my elder brother.”
Paul’s academic excellence had put him in funny situations at times. In 1957, when he was in high school, the Soviets launched the first Sputnik. Around that time, some Russians came to visit Yercaud. There were rumours in the school that they had come to kidnap Paul to work on their space programme because of his talent. The incident still brings a broad smile to his face.
A PhD with a twist
In 1959, after finishing high school, Paul joined a pre-university course at Loyola College in Chennai. He always fancied a career in Maths and Physics. But lack of guidance, coupled with limited financial resources, ultimately led him to join the National Defence Academy (NDA), which was completely free, given his father’s navy background.
Defence services was not the career he wanted, given his academic interests. Even the NDA faculty would tell him that he was in the wrong place. Nonetheless, he graduated at the top of his batch, bagging the president’s gold medal and achieving the position of academy cadet captain.
But his knack for science and technology stayed alive. In 1964, he joined the Naval College of Engineering at Lonavala and opted for the Electrical Engineering branch. While this professional training programme wouldn’t earn him a BE degree, he was the top student during the five years he spent at the institute.
It didn’t take long for the navy officials to figure out Paul’s academic genius. Although the lack of a formal BE degree made him ineligible for enrolment in a higher engineering course, the navy nominated him for the ME course at IIT Delhi. Professor PV Indiresan, who later became Paul’s mentor, impressed with his academic excellence, convinced the IIT Delhi senate to waive the requirement of a BE degree.
According to Paul, he was probably the first officer from the navy to get such an exemption. Later, the government decreed that the professional training received by former NDA officers was equivalent to a BE degree. Many bright navy officers benefitted from this move, which redefined the course of the Indian Navy.
But destiny had other plans for Paul.
Indiresan soon figured out that Paul’s aptitude was way above the ME curriculum. He suggested transferring Paul to a PhD programme. But, the big hurdle was to convince the higher-ups in the navy.
He wrote to the then vice-chief of naval staff, vice-admiral Krishnan to allow Paul to shift to a PhD programme instead of an ME. “The navy does not need scientists,” the vice-admiral wrote on the file, rejecting the proposal.
However, after a lot of persuasion, the navy relented on the condition that Paul would be given only two years — the duration of the ME course — to finish his research work. By the time Indiresan got all the approvals, only 18 months were left for the research work, but in yet another show of brilliance, Paul completed it within that time frame. Under normal circumstances, it would have taken at least four years to complete a PhD.
Years later, Paul’s wife Nirmala remembers meeting some of his IIT Delhi professors. “We used to hide from this guy [Paul] because he would have read two chapters ahead of what we were teaching. We used to keep our fingers crossed that he doesn’t start asking questions,” they told her.
At IIT Delhi, Paul had the opportunity to meet professor Thomas Kailath, another mentor and later a colleague at Stanford University, who visited the campus to teach filtering theory, which eventually became Paul’s research area. Kailath was so impressed by Paul’s thesis on non-linear and linear filtering that he invited him to Stanford University to deliver lectures.
The PhD flagged off Paul’s amazing and diverse achievements in the field.
A submarine attack opens up new horizons
As they say, things happen for a reason. Joining the Indian Navy had turned out to be a boon in disguise for Paul.
After finishing his PhD research, Paul returned to the navy in 1971. His thesis work was still pending, and he wanted to stay at IIT Delhi for another year to finish it, but the navy was planning a sea duty for him. On Paul’s request, the navy agreed and posted him at Navy Headquarters in Delhi. He had a busy routine — a day job at the Navy Headquarters and nights at the IIT Delhi library writing his thesis.
But destiny had other plans.
In December 1971, the Indo-Pak war broke out. The Indian Navy frigate, INS Khukri, fitted with a prototype of the Sonar 170B modified by Bhabha Atomic Research Centre (BARC), was on a combat-patrol mission when it was sunk in a torpedo action. The sonar was unable to detect the enemy submarine and India lost over 200 brave soldiers, many of whom Paul knew.
In an official navy history record, Paul reminisces that the morning after the sinking of INS Khukri, commodore Chatterjee, who was director of the electrical engineering department at Navy Headquarters, asked him if he knew anything about Sonars. “I don't remember what I told him, but later that afternoon, I accompanied him to Bombay,” Paul recalls.
Chatterjee recommended Paul to lead the Sonar 170B project to improve its performance. Paul noticed some shortcomings in BARC’s approach and proposed to develop an alternative receiver technology using advanced signal processing. The navy also agreed to his request to allow him to work on the project at IIT Delhi.
After some initial hiccups, Paul and his team developed a new technology for Sonar 170B within three months. After extensive trials, the navy approved the new model for deployment in its fleet. Alongside, Paul finished writing his PhD thesis and submitted it around the middle of 1973.
In 1974, Paul received the Vishisht Seva Medal for “distinguished service of a high order” for successfully leading the project to improve the performance of sonar 170B.
A specialist in anti-submarine warfare, the former chief of naval staff, retired admiral Vishnu Bhagwat, collaborated with Paul on sonar-technology development.
He vividly remembers that when he requested Paul to fund higher studies of a couple of brilliant navy officers several years later, he immediately agreed. “I wanted to build an army of mini-Paulrajs across the Indian Navy,” he says.
Admiral Bhagwat is well-known for his support for greater indigenisation of the Indian Navy’s technology base. Emphasising the importance of having in-house technology experts, he adds, “If the opponent is technologically so ahead that you can’t take it on, that’s a threat.”
On his part, Paul says, “I admire and share admiral Bhagwat’s lifelong quest for greater and authentic indigenisation of the Indian Navy’s technology base.”
APSOH: inexperienced team, limited resources, so what?
After the sonar project, Paul went for a research fellowship programme on signal-processing algorithms at Loughborough University, UK, in 1974. The navy used to send Paul on many such programmes when he was not involved in any major project. ”When they didn’t know what to do with him, they sent him off,” says Nirmala Paulraj jokingly.
Paul spent a year and a half at Loughborough University and on orders from the Naval Headquarters, he visited some sonar manufacturers in the UK and France at the end of the programme to assess the design and performance of the new panoramic sonars.
On his return, Paul approached senior navy officers with a proposal to develop indigenous next-generation panoramic fleet sonar. Initially, the navy was reluctant, but given the remarkable success of the Sonar 170B project, he was given the green signal. This time, the project was much bigger and more complex.
The navy assigned Paul to DRDO’s Naval Physical and Oceanographic Lab (NPOL) in Cochin in 1976 to lead the development of this new sonar. The project was codenamed APSOH (advanced panoramic sonar hull-mounted).
At first, NPOL didn’t involve Paul in the panoramic sonar project it was already working on. Paul recalls that the poor history of relations between service officers and the R&D community could have been the reason for this.
NPOL had ordered a computer from the US, and it arrived damaged. While at Loughborough University, Paul built a minicomputer by himself and wrote an assembly code for its operating system. He wrote a new boot code for the damaged computer and fixed it. This did the trick, and he was involved in the sonar-project team, which he eventually led and delivered successfully. The project took seven years to complete.
According to Paul, APSOH was the biggest military electronics project in India at that time and one of the biggest indigenous technology commitments from Indian defence services. Improved variations of APSOH are still deployed in the navy’s warships.
In the official navy history, Paul recorded his thoughts on APSOH in retrospect: “Now that I lead aspects of wireless technology at a worldwide level, I have a better understanding of the technology development process in the developed countries. I sometimes compare APSOH with other achievements I see in my new field. I am always amazed as to how such an inexperienced team, with such few resources, pulled off this major project in such a short period. APSOH was an impossible dream that came true for many of us.”
In 1984, Paul received Ati Vishisht Seva Medal for “distinguished service of an exceptional order” for the development and commissioning of APSOH.
Undying ESPRIT
After the APSOH project was completed, the navy rewarded Paul with a two-year fully sponsored sabbatical anywhere in the world to explore new areas. Paul requested professor Kailath to let him join his group at Stanford University. Initially, Kailath declined, saying that he may not be a good fit, as he was more of a practical engineer, and his group worked more on theoretical concepts. But later, on Paul’s persistence, he allowed him to join as visiting faculty. In 1983, Paul moved to Stanford along with his family.
Kailath’s group was working on the estimation of direction-of-arrival (DOA) of multiple signals using antenna arrays. Paul had worked on DOA estimation of a single signal during the APSOH project. The problem at Stanford involved multiple signals, and Paul developed a new approach to solve the DOA problem through an algorithm called ESPRIT (Estimation of Signal Parameters via Rotational Invariance Technique). His hands-on experience of working on sonar projects, combined with an advanced mathematical approach, resulted in a revolutionary solution.
ESPRIT is a topic still taught in universities. Professor Helmut Bolcskei, chair of the Mathematical Information Sciences at ETH, Zurich, says, “ESPRIT is not often mentioned, but it’s a famous invention. I still teach it to my students. It is such an elegant algorithm.”
In 1986, Paul returned to India and founded the Centre for Artificial Intelligence and Robotics in Bengaluru. Briefly thereafter, DRDO proposed his name to lead India’s ambitious light combat aircraft (LCA) project. But, given his past experience with bureaucratic bottlenecks, Paul proposed a different operating structure for the efficient management of the LCA project, which was eventually stalled.
He was later deputed as chief scientist at Bharat Electronics (BEL), where he started two central research labs. During this time, he also built another lab, the Centre for Development of Advanced Computing, in Bengaluru.
That was when Paul started to think about moving to an academic career. But changing course at the age of 46 and his service background posed challenges.
Hinting at how politics within organisations and bureaucracy impacted him, Nirmala Paulraj says, “Stress was never from work. Stress was always from people causing problems.”
Retired admiral RH Tahiliani, former chief of the naval staff in one of the official navy histories, has shared his disappointment with the circumstances that led to Paul’s decision to move to the US: “His departure for Stanford University was a major loss for our country and the circumstances that led to his move may explain why we have so few Nobel laureates from India.”
MIMO’s link with rain and a haircut
In 1991, Paul took early retirement from the navy and approached Kailath again for a post-doc position at Stanford. Kailath offered him a research associate position at Stanford for the interim.
While many were disappointed about him leaving the country, Paul, with his characteristic optimism, always looked at the positives. At the Marconi Prize event, he said, “Coming to Stanford was one of the most fortunate breaks in my life. I am very grateful for the opportunity.”
At Stanford, renowned math professor Gene Golub was working on a project for the US Air Force to intercept and separate interfering signals arriving from different directions. He involved Paul in this project.
Paul built a prototype to analyse and understand the signals in the real world instead of using software-based simulators. Using cordless phones as different signal sources and a base station with multiple antennas to receive signals, he experimented with a range of signal-separating algorithms. The system was able to parse the signals effectively when the phones were far apart, but failed when they were too close.
And then it started raining.
The team moved the set-up indoors and to its surprise, the system was capable of separating the signals even when the phones were just next to each other. Paul started to think of the logical explanation behind this. It didn’t take him long to figure out that it was the multiple-path propagation of signals that bounced from the walls and arrived at a different angle at the base station (despite the phones being next to each other) that helped the receiver separate them. Though this finding didn’t help in cracking the US Air Force problem, it planted the seed for the invention of MIMO.
One day, as he was thinking about this interesting finding while having a haircut, a Eureka moment happened: What if he put two antennas on the transmitter and use two antennas on the receiver side and send two data streams on the same frequency channel? Wouldn’t the data rate be doubled?
Thus, MIMO was born.
Recalling the incident in one of his interviews, Paul, with characteristic humility, said, “It was rain and some good fortune that led to MIMO’s invention.”
Later, he did some mathematical calculations and figured out that by having multiple antennas (say, n) on each side of the radio link, the capacity of the link could be increased n times without any additional power.
Although companies and investors back then were sceptical about the idea, Paul would go on to have the last laugh and successfully demonstrated MIMO’s feasibility when he founded his first company Iospan Wireless.
Paul explains MIMO thus: “MIMO multiplied the link speed of wireless networks manifold and also improved their range and reliability. MIMO’s speed-up is 4x in most current deployments, with options for 8x. Today’s pervasive 4G-5G mobile and Wi-Fi networks would be impossible without MIMO.”
MIMO-powered wireless networks enable 6.5 billion smartphone users to access the Internet, as well as connect billions of IoT devices. Industry groups estimate the global economic value of wireless networks in 2021 to be around USD7.8 trillion.
“MIMO was a gamechanger for wireless communications. It was what enabled high-speed, high-reliability wireless communications, not only in cellular but also in Wi-Fi,” says Andrea Goldsmith, dean at the School of Engineering and Applied Science at Princeton University, US.
Goldsmith is among the most influential electrical engineering professors in the US. She serves on many of the nation’s advisory positions, including the Presidential Committee on Science and Technology, and is on the board of several companies, including Intel, Medtronic, and Crown Castle. She and Paul were colleagues at Stanford for more than two decades.
It was September 6, 1994, exactly 29 years ago, when the United States Patent and Trademark Office granted the patent for MIMO’s invention to Paul, with Thomas Kailath as co-inventor.
A rare combination
While Paul’s strength in theoretical aspects was nurtured by his mentor, professor Kailath, at Stanford University, his inclination towards developing solutions and applications comes from professor Indiresan, his mentor at IIT Delhi.
Admiral Bhagwat aptly captures this unique combination when he says, “He has this unique ability to carry a concept into mathematical formulations, and then convert it into an experimental project, and convert that project with the technology and the materials available to have the best-in-class product.”
Soundararajan echoes the thought, “He is that rare genius who is not only a scientist, but a visionary and a leader in the true sense of the term.”
Professor Bolcskei of ETH, Zurich, agrees. “He’s an absolutely impressive systems engineer. He combines that with a deep mastery of physics and mathematics. These three things together make him a singular figure … which for a scientist is very rare. That singles him out.”
Bolcskei, well known for his contributions to the theory of MIMO communications and deep neural networks, was a post-doctoral researcher with Paul’s group at Stanford in the late 1990s. “I have watched with pride his contributions at the highest levels to the theoretical foundations of signal processing,” says Paul about Bolcskei.
Bolcskei says he tries to adopt Paul’s constructive mindset — one that is only interested in substance. “If something goes wrong, he will just say, ‘How can we move forward?’ There will never be a clean-up, or trying to know who was responsible. He cares about people. He understands that people are who they are, and we all make mistakes.”
The sentiment is echoed by Aruna Soundararajan, former telecom secretary, Department of Telecom, and chairperson of the Digital Communications Commission. “For him, only the cause matters. He doesn’t look at personalities, he doesn’t look at personal setbacks. He is like Arjuna, who only sees his target,” she says.
“The IAS cadre has produced several outstanding officers, but Aruna Soundararajan stands out even within this elite club. Her intelligence, dedication, and judgement while leading tech-heavy departments have served India very well,” Paul says about her capabilities.
For Paul, it is the collective, and not the individual, that matters. It’s never about him. “He's incredibly humble. He’s also incredibly generous. He spends a lot of his time promoting other people, promoting students, and promoting colleagues.” says Goldsmith. “As a scientist, what differentiates him is his vision and depth of knowledge. There are very few people that span such a broad range of experiences.”
At the felicitation ceremony of the Marconi Prize, professor John Cioffi, the inventor of DSL technology and a colleague of Paul at Stanford, said, “Paul’s technical capability is almost unparalleled. Such people are pretty rare.”
Nirmala Paulraj puts across Paul’s brilliance in a different way, “I used to be a quiz champion. But now, I don’t even Google, I just ask Paulraj and the answer is there. My Google is Paulraj.”
Given all the interactions I have had with Paul, I can say with certainty that he has an aura that none can miss.
Honours and accolades
In all, 265 patents are registered with the US Patent and Trademark Office that have Paul’s name as the inventor or co-inventor. Besides, he has won a host of awards in India and abroad.
While the list is long, here are some of the most prestigious awards and honours that he has received:
- National Inventors Hall of Fame, 2018: Paul was inducted into the US Patent and Trademark Office National Inventors Hall of Fame for the invention of MIMO. Over the past 50 years, 624 scientists have made it to the list. They include Thomas Alva Edison, Guglielmo Marconi, Alexander Graham Bell, Claude Shannon, Nikola Tesla, the Wright Brothers, and Steve Jobs.
- Marconi Fellow, 2014: Again, the invention of MIMO fetched Paul this award, considered the Nobel Prize equivalent for technology pioneers. There are 56 Marconi fellows globally, including Martin Cooper, for inventing the handheld mobile phone; Vinton G Cerf, and Robert Kahn, known as fathers of the Internet, for designing TCP/IP protocols; Tim Berners-Lee, for inventing the World Wide Web; John Cioffi, for inventing DSL; professor Yash Pal, for applying modern communications technology to meet the needs of Indian villagers; and Lawrence Page and Sergey Brin for founding Google.
- IEEE Alexander Graham Bell Medal, 2011: Awarded for exceptional contribution to communications and networking sciences and engineering, Paul received this prize for the application of MIMO in wireless communication systems. There are 55 recipients of this award globally.
- Padma Bhushan, 2010: Paul received India’s third-highest national award for his contributions to the Indian Navy.
“In telecom, there are two top recognitions — the IEEE Alexander Graham Bell Medal, which has a bias towards theoretical contributions, and the Marconi Prize, which honours contributions that convert breakthrough ideas into products benefiting billions of people. I am incredibly honoured to have won both,” Paul said during his address at the Marconi Prize felicitation event.
Then President of India, Pratibha Patil presents the Padma Bhushan to Prof. Arogyaswami Joseph Paulraj in New Delhi on March 31, 2010.
The family man
While juggling between the sonar 170B project and completing his PhD thesis, Paul got married in February 1973 to Nirmala. Earlier this year, they celebrated their 50 years of togetherness. According to Paul, his wife has always been his biggest support. “It has been 50 years of married life and Nimi has persevered in supporting the family through life’s inevitable challenges,” says Paul.
They are blessed with two daughters. Mallika, who is into environmental sciences, graduated from Stanford and later studied at LSE, London. Nirupa, who studied medicine at Manipal, and is a physician in Las Vegas.
Paul always wanted both his daughters to explore technical careers and study at Stanford, but now his only hope is from the grandchildren, who Nirmala Paulraj says hide whenever he brings up this discussion.
Nirmala Paulraj says senior officers from the armed services would often tell her, “You have to be the one to make the sacrifice to allow him to achieve his potential.” Now, with great pride, she says, “I feel I have done that.”
Though on a lighter note, Nirmala says, “Behind every successful man, there is a disgruntled wife.” But given the way things have worked out for Paul, she adds that she is very happy and proud to be the disgruntled one.
Commenting about his reserved nature, his brother, colonel Arul Raj, says, “When we all get together, we crack jokes and pull each other’s leg. He is quiet and more philosophical. But that is his nature.”
Arul is India’s foremost military painter. His war paintings adorn many iconic locations – the Rashtrapati Bhawan, Service Headquarters, and military museums and offices. The new National War Memorial in Delhi has six large bas-relief bronze murals of war scenes, which all are based on his paintings.
Commending the legendary talents of his younger brother, Paul says, “He is the pride of our family. And we all love him.”
His heart still beats for India
“I’m not ready to stop work yet. My biggest challenge is finding time for all the things I want to do,” Paul said when he received the Marconi Prize in 2014. About a decade later, he still feels the same.
About to be an octogenarian in a few months, Paul continues to work for the betterment of India. ”I wish I was younger because there is so much to do.”
Commenting on Paul’s love for his country of origin, admiral Bhagwat says, “He is a patriot of high order … a national treasure.”
Paul has articulated an ambitious vision for India and shared it with the Indian government at the prime-ministerial level. He strongly believes that India has the potential and resources to build an ecosystem of world-class universities that will help brilliant scientists and engineers to stay in the country and innovate.
Colonel Arul Raj adds that Paul “has this great dream to see this country [India] come up”.
Paul was the chair of the steering committee of the High-Level Forum for 5G in India, which played an instrumental role in the country’s 5G journey.
He is also on the advisory committee of India Semiconductor Mission, chairing the Fabless Chip Design segment.
Paul identifies semiconductors, aerospace particularly commercial jets, new-molecule pharmaceuticals, advanced instrumentation, and biotechnology as the core areas on which India should focus. He strongly believes that academia, industry, and the government need to work together to make this happen. On this, Soundararajan says, “He knows exactly where each capability is available. He knows the strengths and weaknesses of Indian academia. He knows the strengths and weaknesses of Indian industry. He knows how our policy environment is structured.”
Paul is clued on to developments on the ground. He travels to India almost every other month. He interacts with professors, students, top industry executives, government officials, and policy makers. He wants the government to find ways to target just 5% of the global value chain. That, he says, will be enough to serve as the launchpad for further progress.
“My dream for India is to one day become a leader in innovation-driven advanced-technology industries,” says Paul. He wants it to be a nation with research universities that contribute to human advancement at the highest levels. “An India that rises to become an influential and respected nation – not just for its economic and technological progress, but also for its high values and the way it cares for the least of its citizens. A nation that is a beacon for peace, hope, and reconciliation for all humanity,” is how he sums up his vision.
To make this vision a reality, here’s his advice to the youth of the country: “Nothing worthwhile is ever easy. A worthwhile goal takes hard work, patience, and perseverance. Hard work comes more easily if we love what we do, and we usually acquire that if we are good at doing it. But finding what we are good at is also not easy. More likely, it comes from working hard at something worthwhile which slowly turns into the work we love. Once we find that, many things will fall into place.” He sums up by saying, ”Great people are just ordinary people with an extraordinary amount of determination.”
Paul is a living example of how hard work, perseverance, patience, and determination can lead one to the greatest heights. Given all the contributions that he has made to the country and to the world, it won’t be wrong to say that he is like an Einstein or Newton of today.
As the author of this profile, I feel honoured having met this living legend in person and it was an absolute pleasure to pen down his momentous contributions.
(Graphics by Sadhana Saxena)
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