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[leadership REFLECTIONS] Man Mohan Sondhi

Reflections on My Career at

hen Prof. Nehorai Labs and worked there until my retire- demic atmosphere of the place. That was invited me to con- ment in 2001. Currently, I am a consult- something I had not anticipated in an tribute an article to ant at Avaya Labs Research. industrial research organization. And to this column, I was a I must confess that when I joined add to that, the labs had resources in bit hesitant to Bell Labs, I had intended to stay there equipment and support personnel that Waccept his invitation. I do not really have for just a few years to gain some experi- far exceeded those at a university. Also, any advice for young aspiring engineers ence in industrial research and then top quality facilities were or words of wisdom such as the ones you academia. The research environment, available. (By today’ standards, of will in some of the earlier articles. however, was so attractive that the few course, the computing facility at Bell Also, unlike other writers in this column, years stretched out to 39. Labs in 1962 is laughable. All computa- I have not managed a large group of sci- tions were done on an IBM 704 entists. I headed only a very small group BELL LABS: AN INSIDER’S VIEW in batch mode. The computer had a (about six) of colleagues for a few years. I would like to share with you some of memory of 32 K, and it occupied a large However, Prof. Nehorai assured me that the allure and excitement of working at room in the only air-conditioned build- the “Leadership Reflections” column Bell Labs. Much has already been written ing on the campus. Programs were includes articles that look back on scien- about the preeminence and stature of punched on Hollerith cards and sent to tific careers and the institutions that Bell Labs as a research organization. But the computer via carts. However, by nurtured them. So my article is going to by using examples drawn from my per- the standards of the day, the facility was be about my career, mainly about my 39- sonal experience, I hope to provide a dif- top class.) year association with Bell . ferent, more intimate, perspective. Another thing that struck me imme- My undergraduate training was in Fortunately, a large part of my career diately was the completely free atmos- India, where I earned degrees in physics at Bell Labs was during the era that has phere. Here were world-famous and electrical communication engineering. been called “the glory days” of Bell Labs. luminaries by the dozen, were not I wanted to continue further studies in I am not sure when that era began— barricaded behind outer offices and sec- engineering, but in those days (mid-) presumably just after World War II. retaries. You could just walk up to their no graduate program in engineering was However, the end is easier to identify. offered anywhere in India. So I decided to Slow erosion started in 1984 when AT&T EDITOR’S INTRODUCTION go to America for graduate studies. One of was broken up, even though Bell Labs The author of this article, Dr. Mohan the universities that accepted me was the itself was still kept in one piece. The ero- Sondhi, has had a long career in University of Wisconsin, where I earned an sion picked up speed in 1996 when Bell industrial research in speech process- M.S. and a Ph.D. In 1954, while I was on Labs was up into a part that stayed ing at Bell Labs. In this article he gives the ocean on my way to America, my very with Technologies and another an account of events chosen from his own association with Bell Labs to first scientific paper (on vibrations of part that formed the new AT&T Research illustrate what he believes were the Indian musical drums) appeared in the Lab. And, at least for the area of Bell Labs most noteworthy characteristics of Journal of the Acoustical Society of where I worked, the end came abruptly that renowned lab—emphasis on cre- America. (Air travel those days was by pro- in 2001 with what I call “an epidemic of ation of knowledge, freedom to peller planes and only for the very rich.) I encouraged retirement.” But I am get- choose research topics, and taking a arrived in New York just about when ting ahead of my story. Let me tell you long-term view of research problems Senator Joseph McCarthy was beginning to about some of the qualities of Bell Labs without being tied to development fall from grace. that made it such a unique place and, of products. He closes with a plea for After finishing my Ph.D. degree at wherever possible, to give you some a re-creation of that type of research Wisconsin, I briefly worked for industry examples from my experience that illus- environment. and at a research institute in India and trate these qualities. —Arye Nehorai “Leadership Reflections” taught at the University of Toronto, One of the first things that impressed Column Editor Canada, for a year. In 1962 I joined Bell me at Bell Labs was the essentially aca-

IEEE SIGNAL PROCESSING MAGAZINE [6] JULY 2006 1053-5888/06/$20.00©2006IEEE [leadership REFLECTIONS] continued offices, and they all welcomed you to dis- theory, which was definitely not some- the vocal tract and from them estimate cuss problems with them. thing of direct interest to the depart- its three-dimensional form. This method ment that employed me. (Incidentally, is undesirable for several reasons, the THE IMPORTANCE OF DIVERSITY one of those papers, written in collabo- most important being the need for pro- Diversity was another remarkable aspect ration with David Anick and Debasis longed exposure to X rays. Manfred of the labs. The department that I joined Mitra, actually turned out to be cited far Schroeder suggested using acoustical was ostensibly concerned with various more than any of my papers in acoustics measurements to determine the shape aspects of speech processing, cod- or speech.) and derived a method valid when the ing, and transmission. Everyone in the Emphasis was on doing good science tract is only slightly perturbed from a department was interested in one aspect and creating new knowledge without the uniform cross section. . Gopinath and I or another of speech. But as far as I could immediate goal of practical application. became intrigued by this “inverse” prob- tell, almost none of the members of the Not all research was aimed at developing lem and were able to derive a complete department joined the lab with prior cre- products. The thinking was that with mathematical solution. Later, in collabo- dentials in that area. There were a couple several competent people doing research ration with Jeff Resnick and then with of electrical engineers, a , a phys- with a variety of motivations in an envi- Juergen Schroeter, I was able to reduce ical chemist, a mathematician, and so on. ronment rich with relevant problems, the method to practice and actually pro- And yet, together they were able to pro- some of the research was bound to result duce movies of the dynamic variations of duce some of the best work in the field. in good products. This attitude started the vocal tract. This work did find recog- This approach is in sharp contrast to the changing slowly in 1984, and there was nition in some areas of the scientific modern idea of hiring people who would more and more emphasis on product- community but turned out not to be too “hit the ground running.” oriented research. Some revisionist useful for speech work. Yet its scientific Another aspect of diversity is worth claims have been made to the effect that merit was appreciated, and the work was mentioning. It was the acknowledge- research at Bell Labs was always directed supported at Bell Labs for several years. ment that people have various motiva- towards a product, and the invention of As an example of emphasis on long- tions for doing research. Some (like me) the has been cited as a prime term research, I might mention my work approach it as puzzles to be solved, oth- example of this. I do not agree with that on cancellation. In long-distance ers to a fundamental discovery or assessment. And as far as the invention , echoes are generated at points to make a lasting contribution to society, of the transistor is concerned, I distinctly of impedance mismatch, mainly at the yet others to invent commercially suc- remember a symposium in honor of the interface between the long-distance net- cessful products, and so on. It was recog- 50th anniversary of its invention. Several work and the local network. Several satis- nized that good research can be done scientists who had participated in that factory methods of combating these with a variety of such motivations. activity in the were at this sympo- echoes had been invented over the Freedom to choose the line of sium. And several of them made state- decades since the advent of long-distance research one wished to pursue was one ments to the effect that the study of telephony. In 1962, however, one week of the most enticing aspects of working was presented to them after I joined Bell Labs, the era of satellite at Bell Labs. I can say without hesitation as an area worth investigating with the telephony was ushered in with the launch that in my 39 years there, I was not once potential of yielding breakthrough prod- of the first , asked, let alone imposed upon, to work ucts. However, their charter was to study . It was anticipated that satellite on some specific problem. And I am sure semiconductors and develop an under- communication would ultimately be via this experience was shared by just about standing of their properties, without the geostationary satellites, and these pro- everyone in the basic research part of specific aim of developing a product. duce round-trip delays of as much as 600 Bell Labs. The idea was for managers milliseconds. With such long delays, the (e.g., department heads and directors) to KNOWLEDGE AND RESEARCH known methods of dealing with echoes provide a problem-rich environment and Here are some examples from my per- were shown to be quite unsatisfactory. A then let individuals decide what they sonal experience to illustrate the empha- new method was needed, and John Kelly wanted to work on. Some very broad sis on creation of knowledge and the started thinking about it in the early directives obviously existed, and I emphasis on long-term research. . He proposed the device now assume straying too far from them might A problem of interest in speech sci- known as an echo canceler and invited have been discouraged. ence is to determine the continuously Ben Logan and me to join him in devel- Collaboration among people in very changing cross-sectional area along the oping it. Anthony Presti and I made the different parts of the labs was encour- vocal tract in the process of producing first (analog) prototype of the canceler aged. My collaboration with several speech. I was made aware of this problem around 1996. Due to Kelly’s untimely members of the mathematics depart- early in my career by James Flanagan. death, I ended up writing the first paper ment is an example of this. That collabo- Early procedures for doing this used X- laying out the mathematical properties of ration yielded several papers in queuing ray movie cameras to record side views of the device in 1967. In the 1970s, Debasis

IEEE SIGNAL PROCESSING MAGAZINE [8] JULY 2006 New & Noteworthy from Birkhäuser Mitra and I collaborated in deriving sev- It may be argued that this attitude eral basic properties of the canceler. towards industrial research was possible The important thing to note here is only because of the special, regulated A Software-Defi ned GPS that while all this work was being sup- monopoly structure of the old AT&T. And and Receiver ported, it was not clear if and when a it may be argued that to show an annual A Single-Frequency Approach DENNIS M. AKOS, University of Colorado, commercial application of the device profit, business value becomes of para- Boulder; KAI BORRE; NICOLAJ BERTELSEN; would be realized. The analog implemen- importance, and industries cannot PETER RINDER; SØREN H. JENSEN, all, Aalborg University, Denmark tation was prohibitively expensive, and afford the luxury of such research. There This book and accompanying DVD explore the integrated circuits were still in the is, I am sure, some truth in both these use of new technologies in the area of satellite future. However, we were encouraged to assertions. However, I believe that it is in navigation receivers; coverage discusses re- work on “impractical” ideas under the the national interest to have a ceiver architecture based on software-defi ned assumption that eventually digital tech- of this type: a laboratory where industrial radio techniques. MATLAB-based exercises and examples on the DVD allow readers to nology will make them economically fea- research is done in a university-like change parameters and test in a sible. It took over 15 years for the atmosphere, but where, unlike at a uni- hands-on way. commercial application of echo cancelers versity, the environment is rich with prob- For information on optional, supplementary to begin, with the implementation of a lems of direct interest to industry. hardware that may be used with the book/DVD, please visit www.springer.com/0-8176-4390-7. canceler on a chip in 1980 by Don Perhaps a national laboratory is the Duttweiler and Y.S. Chen. Later, of answer. Or perhaps a laboratory run by a 2006/APPROX.192 PP., 80 ILLUS./SOFTCOVER ISBN 0817643907/$79.95 TENT. course, the device was deployed by the consortium of industry could be formed. APPLIED AND NUMERICAL HARMONIC ANALYSIS millions on the network and It is imperative that means be found to set yielded more than a billion dollars of up such a laboratory. It is important that a The Evolution of revenue to the owners of Bell Labs. certain portion of industrial research be Applied Harmonic Analysis Another example of aiming at a dis- done without the emphasis on immediate Models of the Real World ELENA PRESTINI, Università di Roma tant future is provided by a more recent application. The exigencies of developing “Tor Vergata”, Italy application of echo cancellation. During products and services create an atmos- “In each of the application areas the author the 1990s, I started thinking about the phere of rapid changes that may be provides a sketch of the underlying mathemati- problem of canceling echoes in a stereo- likened to a rollercoaster ride. That can be cal tools borrowed from harmonic analysis… phonic teleconference. It turns out that thrilling, but it is not possible to think The author discusses the topics of the fast Fou- rier transform, signal sampling, quantization, cancellation of echoes in such a multi- about the distant future while riding a and fi ltering that are mainstays of modern digi- channel situation is qualitatively rollercoaster. And some amount of relaxed tal communications… Perhaps the most im- different from cancellation in the sin- thinking about the future is necessary. portant of all applications [covered] are the gle-channel case. In collaboration with recent ones to medical technology.” —ZENTRALBLATT MATH Dennis Morgan, Jacob Benesty, and AUTHOR 2004/XIX, 349 PP., 169 ILLUS./SOFTCOVER Joseph Hall, I spent a considerable Man Mohan Sondhi ISBN 0817641254/$59.95 amount of effort on this problem, and ([email protected] APPLIED AND NUMERICAL HARMONIC ANALYSIS we were able to come up with some labs.com) is a consult- Time-Frequency and interesting and useful solutions. Again, ant with Avaya Labs Time-Scale Methods this work was encouraged even though Research, New Jersey. no immediate use was expected. More Prior to 2002, he had Adaptive Decompositions, Uncertainty Principles, and Sampling than ten years later there are still no been with Bell JEFFREY A. HOGAN, University of Arkansas, commercial applications of this work. Laboratories for 39 years as a member of Fayetteville, ; JOSEPH D. LAKEY, New Mexico To date it remains a conjecture, the technical staff and later as a distin- State University, Las Cruces, although I believe a good one, that guished member of technical staff. He “[O]ne may view the present book as a contin- uation of the famous textbook of Ingrid eventually most teleconferencing will received his Ph.D. degree from the Daubechies [Ten Lectures on ]… In use stereophonic (in general multichan- University of Wisconsin in 1957. He is a my opinion, the two books nicely complement nel) transmission and will therefore coauthor of the book Advances in each other and both are a ‘must have’ for every- require stereo (or multichannel) echo Network and Acoustic Echo Cancellation one who is interested in a deeper understand- ing of time-frequency and time-scale methods.” cancelers. (2001) and coeditor of Advances in —ZENTRALBLATT MATH I could give several other examples Speech Signal Processing (1991). He was 2005/XXII, 390 PP., 22 ILLUS./HARDCOVER from my personal work in other areas elected a Bell Laboratories (1998) ISBN 0817642765/$74.95 such as and speech and was awarded the Bell Laboratories APPLIED AND NUMERICAL HARMONIC ANALYSIS synthesis, but the above examples suffice Arnold trophy (1997), the IEEE Eric to illustrate my view of Bell Labs’ com- Sumner prize (1998), and the IEEE mitment to long-term research aimed Signal Processing Society Best Paper Birkhäuser primarily at the creation of knowledge. Award (2001). [SP] Boston · Basel · Berlin www.birkhauser.com 012486x IEEE SIGNAL PROCESSING MAGAZINE [9] JULY 2006