December 9, 1971, 8:00 p.m.: INS Khukri, an Indian naval anti-submarine frigate, is torpedoed by a Pakastani submarine at close quarters. The ship sinks within two minutes. The Pakistani sub’s sonar range was nearly twice that of the INS Khukri’s.

December 10, 1971, 6:00 a.m.: A young Arogyaswami Joseph Paulraj is roused from his hostel room at IIT Delhi and taken to Bombay, where he inspects the sonar systems on other Indian ships. The Navy asks him if he can work to improve the sonar. Paulraj agrees.

Back at IIT Delhi, Paulraj began work on the new project. “We developed a new sonar using some of the old core system, and this dramatically improved the sonar performance. The new model was manufactured and fitted in many Navy ships from 1975 onwards,” says Paulraj.

Though the Indian Navy was delighted with the new model, it wanted the world’s top sonar for its fleet. Unfortunately, the world’s best - U.S.-made - sonar was not available to India. Paulraj and a few others managed to convince the Navy that an advanced sonar system could be built indigenously. It wasn’t easy, recalls Paulraj. “We had little track record to back up such dreams. And I was pretty green too,” he says now. Nevertheless, the Navy obliged and soon the APSOH (Advanced Panoramic Sonar Hull mounted) was rolling. Today, the APSOH (and its variants - HUMVAD, HUMSA) are the backbone sonar systems of the Indian fleet.

StanfordFor over a decade, Paulraj, now a professor at Stanford, has been absorbed in developing a new technology that could make wireless broadband a reality. His goal is to expand the bandwidth of today’s constrained wireless spectrum.

The challenge is to provide them access at multi-megabit data speeds. With spectrum in short supply, carriers are looking at all sorts of techniques to squeeze more traffic through their existing spectrum.

MIMO

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