Significant Contributions to Science and Technology
The research and development activities pursued have been broad based and are of an applied nature. These efforts were tuned to be responsive to the changes in the national and the international aerospace electronics scenarios and also to the revolution in computers, computing techniques and informatics.
Leadership in Establishing Modern Centres
Prof. N. Balakrishnan was responsible for establishing SERC, one of the best high performance computing centres in India. He was responsible for planning and realization of the functionally distributed centre. This centre which was established braving the denials from the United States, is currently used by over 2500 users. The campus wide Gigabit backbone is the largest in the country and has over 3000 Internet nodes and is considered a technology demonstrator worth emulating. The Supercomputer Education and Research Centre created by Prof. N. Balakrishnan is a national asset. The centre has also become the nerve centre of many an Information Technology initiative in the country.
The experience of building such innovative Computational Environments has helped Prof. N. Balakrishnan to work with TIFAC/DST in creating 7 High performance computing centres across the country, in augmenting 9 Bio Informatics Centres through DBT and in acting as the Chairman of Committee to decide on the Supercompter at the NCMWRF.
The centre has under the leadership of Prof. N. Balakrishnan, established nearly eight modern research Laboratories and is the recipient of many grants including the Shared University Research program of IBM- offered first time to a University in the Asia Pacific region, Microsoft, Fijutsu, Hewlett Packard, TU Delft, Philips, LG, Tata Consultancy Services and Intel with many more in the pipeline.
The Centre from a mere Computer Centre has blossomed into a Research and Education Centre offering Research Degrees and a novel M. Tech programme in Computational Science.
Prof. N. Balakrishnan is the National Coordinator for the Creation of Computer Emergency Response Team of India – CERT-IN. CERT-IN will be operational soon–one at New Delhi with the hot stand by and research support from IISc.
Prof. N. Balakrishnan was also instrumental in the creation of the National Centre for Science Information and its first Computerised Current Awareness Service. In the early 80's, realising the need for use of computers in informatics, Prof. N. Balakrishnan developed a set of computer codes for the retrieval of bibliographic information using computer compatible commercial databases in five areas of science viz Physics, Electronics, Computers and Control (INSPEC), Mathematics (MathSci), Geology (GEOREF), Chemistry (ChemAbs) and Biology (BIOSIS). Today the centre has grown to a national centre and serves the scientists working in around 120 Indian Universities.
He also played a key role in the creation of the Centre for Microprocessor Applications at the Institute in the early eighties and through this centre trained 150 engineering college teachers in Karnataka and Andhra through 5 week intensive training programs. These courses paved the way for the introduction courses on microprocessors in the engineering colleges.
Currently, Prof. N. Balakrishnan is the Indian PI for the Million Books to the Web Universal Digital Library Project-an International Initiative involving USA, China and other countries. Under this project which brought in more than 2 M$ worth of hardware through grants from NSF, USA, Prof. N. Balakrishnan and his team have (http://184.108.40.206):
1. Developed a Technology to take 500 pages of a book in two hours time to the Web without having to cut the book
2. Established more than 15 centres around the country
3. Took more than 16000 books to the web
4. Built and/or evaluated appropriate technologies for Example Based Machine Translation from English to Hindi, OCR, search engines and summarizers in Indian languages and English
This has clearly put India as one amongst the World Leaders in Digital Libraries.
Prof. N. Balakrishnan and his colleagues in IISc and TUN, France have built all the necessary Technologies for developing courseware and delivering them through the web and this has sown the seed for the First Indo-French Cyber University (FICUS). Prof. N. Balakrishnan is the National Coordinator for this programme.
Prof. N. Balakrishnan has established excellent schools of research in Numerical Electromagnetics, High Performance Computing, Information Security, Digital Library and Language Technologies, Speech Processing and Multimedia. So far 22 students have obtained their research degrees at the Institute (Appendix B) and 5 more are currently working for their research conferment.
He started his career as a member of the Guidance and Control Laboratory of the Department of Aerospace Engineering. His colleagues and he were the first to design flight-worthy missile guidance hardware for radio-controlled sighting and command. Prof. N. Balakrishnan later extended this work to develop novel code division multiple access system for secure and error-free command and control of multiple missiles, data compression schemes for satellite imagery and video and their on board realization and to the study of phased and active aperture radars for guidance applications.
Numerical Electromagnetics, High Performance Computing and Polarimetric Radars:
The synthesis of conventional and mono pulse antenna arrays formed the focus in the early eighties. Subsequently, attention has been directed towards predicting the radiation characteristics of antennas mounted on satellite/launch vehicle structures through computational means. To this end, the wire grid model of the BHASKARA satellite along with the method of moments (for structures smaller compared to the wave length), the Spectral Iteration Technique (SIT) (for structures comparable in size to wavelength) and the Geometrical Theory of Diffraction (GTD) (for large structures) have all been pursued. The studies included the ray tracing and the EM and geometrical modeling aspects as well and have culminated in the development of a comprehensive set of computer codes for predicting the modification to the radiation characteristics of antennas due to the presence of aerospace bodies.
The work described above brought about a level of confidence in EM scattering simulation that only needed experimental verification. The selection of site for the installation of Instrument Landing Systems (ILS) is non-trivial and experimental means to this end are time consuming and expensive. In the light of this, improved theoretical prediction of the effects on uneven terrain on the glide slope of the ILS assumes significance. Using flat plate modeling derived from actual terrain profile and the scattering models based on Uniform Theory of Diffraction (UTD) and the Uniform Asymptotic Theory (UAT), the quality of the glide slope has been evaluated by computing the EM field and the Differential Depth of Modulation (DDM) signal. The theoretical results have been compared and found to agree well with those measured at two airport sites in India. This comparison also brought out the fact that the inclusion of terrain impedance considerations improves the accuracy of theoretical prediction of the aberrations and kinks in the glide slope. Another study related to systems aspects of Microwave Landing Systems has also been completed.
The problem of designing efficient radar signals for the rejection of delay-Doppler clutter has been pursued. Using non-linear optimization techniques, a large body of design data have been developed for arbitrary delay-Doppler clutter distributions. The family of signal waveforms designed included continuous and discrete phase coded, frequency coded and phase and frequency coded signals.
The experience in modeling the scattering from complex targets and that in radar signal processing were fused through an international collaboration. A major part of the research efforts was devoted to modeling the EM scattering from hydrometeors (dielectrics and coated dielectrics) and their verification using multi-parameter - Doppler and polarization, radar observations. The level of collaboration with the scientists at NSSL and those at Colorado State University (CSU) have been continuously maintained through electronic mail and all the modeling and computing algorithms were developed in coordination at the Supercomputer Education and Research Centre at the Indian Institute of Science in whose creation Prof. N. Balakrishnan played a very vital role.
Studies of scattering from hydrometeors like rain, hail, graupel and snow are complicated because of the differing sizes, shapes and distributions in which they occur in nature. The scattering from such poly dispersed scatterers further complicates the inverse scattering problem of hydrometeor identification and estimation from polarimetric radar returns, due to the imprecise knowledge of dielectric constant of the scatterers. The contributions in the area of polarimetric radar meteorology, have aided in evolving a framework for interpretation of radar echoes and contributed towards improved microphysical insight into the meteorological processes. Major amongst them is the introduction of a new algorithm to obtain zero-lag correlation coefficient between horizontally and vertically polarized echoes, derivation of its statistical properties and establishing its meteorological significance. The other noteworthy contributions include an algorithm to measure and interpret the differential phase shift upon scattering, a rain-hail boundary in the Zh- Kdp space and a novel non iterative method of correcting for the attenuation.
All the above studies have been validated now with radar data from several severe storms. In a very coordinated experiment involving two coherent radars (one with polarimetric capability) and a KING AIR aircraft with a 2D probe, the comparisons of the scattering computed from 2D probe samples of hydrometeor sizes, scattering computed from a melting model and the remote radar measurements, have been demonstrated to be in close agreement vindicating the sophistication of the scattering models developed. One of the very first measurements reported in the literature wherein the polarimetric and Doppler measurements have been used to qualitatively and quantitatively explain the microphysics of a severe hailstorm, resulted from this study. The engineering modifications required for introducing polarization capability in NEXRAD (NEXt generation RADar) like radars have also been studied in detail. The result of this study has been one of the motivating factors for the NWS, USA to change the polarization basis from circular to linear in all the NEXRAD radars. The use of polarization techniques to satellite borne radar observations for global coverage has been recently shown to be realizable for the first time and this work has far reaching significance in establishing the use of satellite for global rainfall measurements. The work on Polarimetric Radars by Prof. N. Balakrishnan are highly cited and have been reported in many of the world’s top journals such as Journal of Atmospheric Science, Journal of Applied Meteorology, Monthly Weather Review and the Journal of Atmospheric and Oceanic Technology.
The experiences gained in accurate modeling of the scattering from dielectric and coated dielectric hydrometeors have been directly applied to RCS modification of aircraft and its management in an effort towards stealth design. A comprehensive formulation using the Extended Boundary Condition Method has been made to predict the RCS of complex targets coated with a chiral medium. This method is the same as that developed in the work on scattering from weather targets and is making greater impact in the design of low observable Indian aircraft and missiles.
Using full wave solutions of the EM equations, the scattering from rough surfaces has been modeled for predicting the clutter characteristics from vegetated land, urban land and sea surface. These predictions have been validated using the first Indian airborne radar over Indian terrain. The results indicate that the clutter distribution predicted from the scattering model and that seen in the actual measurements are in close agreement. This has fed critical inputs to the design of India's first Airborne Surveillance Platform.
The advances in computers have stimulated research into solving the scattering from large structures through the use of Computational Electromagnetics (CEM). Iterative techniques using CG method and the fast multi-pole method for the rapid solution of the integral equations that arise in EM have been successfully developed. This work along with that on polarimetric radars have been extended to radar recognition so that the Indian radars of the future will be capable of target recognition than mere detection. This innovative recognition technique that identifies targets with small material and geometrical variations has opened up many research prospects that would direct the future radar research in India and elsewhere.
Prof. N. Balakrishnan and his team have developed a parallel MoM to predict the RCS of aircraft like LCA and Mirage at frequencies beyond 3 GHz. This is considered very significant even by world standards. Using a repertoire of techniques such as PTD, UTD, FDTD, FEM and MoM Shooting and bouncing of rays, Prof. N. Balakrishnan’s team has been able to develop operational level RCS Prediction codes for use by DRDO and ADA for predicting the RCS of LCA and Mirage class of aircraft.
The Finite Difference Time Domain Method (FDTD) has been fully developed in its parallel form with a very novel method of introducing the Absorbing Boundary Conditions based on Chiral boundaries. This unique technique has extended the applicability of FDTD to a class of aircraft that include the Nation’s prestigious Light Combat Aircraft in estimating its RCS.
An edge based Finite Element Method has been developed for applications for complex scatterers with sharp edges.
Narrow wall slots and shaped reflectors are often used in the design of airborne antennas. Powerful numerical techniques have been developed for their accurate design and these have been validated using experimental data. This is being used in the design of antennas for an Indian airborne radar.
Information Security, Networking and Multimedia:
Prof. N. Balakrishnan and his coworkers have developed:
1. A network-monitoring tool that can work at very high speeds.
2. A Secure Banking System authenticated using smart cards.
3. A tool for survivable network design for the national networks.
4. Host and network based Intrusion Detection systems.
5. An Automated Intrusion Reporting system like AirCERT for flow based Intrusion analysis
6. A firewall
7. A network security policy generator
8. Active Routers for delivery of MPEG packets.
9. A real time MPEG encoder for satellite applications.
10. A VoIP Capture system
11. A robust Speaker Identification system
12. A robust speech recognizer
and many more. All of these are based on state of the art design and most of them are in operation in the fields contributing to the strategic initiatives of the country.
Sponsored and Consultancy Research Projects
Prof. N. Balakrishnan has been very active in pursuing sponsored research of relevance to the nation. He has currently more than 30 sponsored research and consultance projects with a total outlay of more than Rs 16 Crores. (Appendix C). This does not include the grants obtained for the ICOSER for setting up High Performance Computing Environments (Rs 7 Crores), setting up of the SERC ( A one time grant of Rs 18 crores in 1992 and an annual grant of Rs 5 Crores) and group grants like NIMITLI (Rs 1 Crore) and the Computational Genomics Programme of DBT.
Contributions to Science and Engineering Management
Prof. N. Balakrishnan is the Chairman of several PARCs including that for LCA Multimode radar and Clutter Characterization, member of the review teams of prestigious programs such as Falcon (ADE), PAYAL (NPOL, Cochin), ASP (CABS), Radar Cross Section (ADA) and the ECCM of airborne platforms (LRDE). He was the Project Management Board Member of CABS and a member of the Council of Air Force Training College. He was/is a consultant to ADA, CABS, LRDE and ADE.
Conference chairs/invited lectures and National and International Committees for S&T Management etc
Prof. N. Balakrishnan has been associated with more than 100 International/National Conferences/ Symposia and/or delivered invited lectures in India and abroad.