Helmut Bolcskei’s Tribute to Paulraj


Distinguished ETH Professor Bolcskei is a long time friend and colleague of Paul and included many anecdotes in the speech introducing him at the award ceremony.

Dear Professor Sir Payne, Dr. Cerf, Marconi Fellows, Consul General Parthasarathi, Prof. Kailath, Prof. Paulraj, colleagues, ladies and gentlemen,

In describing who we came together to celebrate tonight, let me start with a quote by the American baseball-philosopher Yogi Berra, who said: “If you get a guy that can play a couple positions, it helps you out a real lot.”

The story of Paulraj’s invention of MIMO wireless technology is succinctly captured by the following quote by Mahatma Gandhi: “First they ignore you, then they laugh at you, then they fight you, then you win.” Today MIMO technology is at the core of virtually all broadband wireless communication systems with billions of users worldwide.

It all started in 1991 when Paulraj, after a highly successful career of 31 years in the Indian navy, retired as a commodore, a rank equivalent to a 1-star general, and joined Stanford University as a research associate with Prof. Thomas Kailath, who is with us tonight. Former Chief of the Naval Staff Admiral R. H. Tahiliani, upon learning about Paulraj’s Marconi Fellowship, said “The Navy is enormously proud of Paulraj’s achievements and will remain always indebted for his landmark development of the APSOH sonar.” This sonar system is still in the news in India. Admiral Arun Prakash on the occasion of the recent commissioning of the INS Kolkata, the biggest Indian-built war ship to join the India navy, commented on what he considers one of the biggest success stories of technology developed in the Indian navy: “The provenance of the Humsa sonar goes back to 1975 when a brilliant naval electronic engineer, Lieutenant Arogyaswami PaulRaj, led a team to develop an advanced panoramic sonar; then at the cutting edge of technology.”

A few months after joining Stanford in 1991, Paulraj started working on the problem of signal separation in the course of a DARPA project. Because of his practical bent, he bought a few 900MHz phones, put them on the same radio frequency channel, and tested his ideas outdoors. When the phones were sufficiently far apart things worked out fine, just as theory predicted. However, when the phones got too close to each other it turned out impossible to tell their signals apart. One day it was raining and Paulraj moved the experimental equipment indoors. He observed that suddenly it was possible to separate the signals coming from two people walking next to each other, seemingly violating what theory said. Building on Yogi Berra’s insight that: “In theory there is no difference between theory and practice. In practice there is.”, Paulraj quickly realized what was happening. The signals transmitted by closely spaced phones bounced off the walls experiencing what is called multipath propagation and came back looking very different so that now they could be separated.

Two days later while having a haircut at the barber’s he realized that he could use this principle to put two antennas on a cell phone and send out two independent data streams which the receiver, also equipped with two antennas, could separate provided the environment looked busy enough, or in technical terms if there was enough scattering.

This idea, called spatial multiplexing, multiplies data rates by creating “parallel spatial data streams” within the same frequency channel. A patent was filed in Feb. 1992, issued in Sep. 1994, and MIMO wireless technology was born. Before I forget, Paul, it would be great if you could give me your barber’s address. I would like to sign up for a haircut as long as I have some hair left to be cut.

When I told this story a colleague, who knew about Paulraj’s involvement in India’s combat jet development program, he told me: “Helmut, the only consolation we can derive out of this story is that at least he did not invent MIMO wireless during his flight training on a Russian MIG 27.”

Paulraj initially faced a lot of skepticism in attracting the wireless industry’s interest in MIMO technology. Research funding for MIMO was also difficult to get. This skepticism was partly because MIMO was leaps ahead of where the industry stood.

In 1993, Paulraj, by then a Research Professor at Stanford, started an Annual Smart Antennas Workshop, which became the pivotal event in this emerging field. These workshops and the seminal papers in 1996 by researchers at Bell Labs (most notably by Jerry Foschini) finally brought MIMO into the spotlight of the research community.

Paulraj built a large group on MIMO at Stanford that graduated over 50 doctoral and post-doctoral students. I feel privileged to be among Paulraj’s disciples. Paulraj epitomizes the principle of a good teacher telling you where to look but not what to see.

On behalf of all your disciples, thank you, Paul, for setting a shining example of integrity and dedication, and for pouring your soul into transforming our lives.

By 1998 Paulraj was convinced that MIMO could be commercialized. Taking leave from Stanford, he founded Iospan Wireless (initially known as Gigabit Wireless). At this point, there was still widespread skepticism about the practical feasibility of MIMO and venture funding became available only after Paulraj demonstrated a 3×3 MIMO radio built with personal funds. By 2001 Iospan had firmly established that MIMO offers significant value in practical wireless communication systems. With the collapse of the Internet bubble, however, Iospan was not as commercially successful as it could have been and was sold to Intel in 2003.

Heeding Thomas Edison’s advice “Many of life’s failures are people who did not realize how close they were to success when they gave up.” Paulraj went on in 2004 to co-found Beceem Communications, which brought MIMO technology to fruition and was acquired by Broadcom in 2010.

In the meantime, the MIMO-OFDM air interface, initially developed at Iospan Wireless, was adopted for the widely used LTE standard and the IEEE 802.11/WiFi standard. The total commercial shipments of MIMO-powered devices exceeded 2 Billion in the year 2012. We are now entering an even more exciting era of smart phones, tablets, smart watches, and mobile Internet, with billions of new devices coming into use in the next few years, the majority of which will incorporate MIMO technology.

“MIMO wireless” has become a term that has left the realm of the tech world. It was mentioned, for example, by Phil Schiller, senior VP of marketing at Apple, during his presentation of the iPad Air a year ago. The janitor who installed new WiFi access points in my lab at ETH last year proudly told me that they feature MIMO wireless.

Few people know that Paulraj’s accomplishments were completely self-taught. As a naval guy he never received much formal training in mathematics. His first encounter with calculus was when he taught himself Ito Stochastic Calculus while doing his PhD on non-linear filtering. Why learn to walk first when you can climb immediately? Paulraj taught himself linear algebra when, during a sabbatical at Stanford in the mid 1980s, he worked on algorithms for direction finding. The result was the famous ESPRIT algorithm, developed jointly with Richard Roy and Thomas Kailath.

I would like to take the liberty to close on a personal note. I have known Paulraj for over 15 years and have experienced him as a person of utmost integrity, always putting the interests of his students, employees, and colleagues first. His qualities are aptly summarized by Thomas Kailath, in an introduction to the book published on the occasion of Paulraj’s 60th birthday in 2004. “Paul has been, at different points, in his career a scientist, engineer, teacher, manager, and advisor — sometimes many of these at the same time. And to everything he has brought dedication, vision, and humanity, which, combined with his scientific and technological abilities, has transformed and enhanced everything he has worked on.”

Despite his success Paulraj stays true to what the Austrian composer and former principal conductor of the New York Philharmonic Gustav Mahler once said “The point is not to take the world’s opinion as a guiding star but to go one’s way in life and work unerringly,

neither depressed by failure nor seduced by applause.” I am sure that Paulraj will not be seduced by our applause tonight, but he nevertheless deserves it.