Faster wireless technology
Finalists for the European Inventor Award 2016
The ingenuity of Paulraj and his team's invention is that it overcomes a fundamental limitation of the wireless spectrum, namely that bandwidth is finite. Paulraj first began working on solving this problem nearly 25 years ago and turned to the idea of spatial multiplexing - adding more antennas to deliver more information on the same channel. Along the way the electrical engineering professor approached two of his post-doctoral students - David Gesbert and Robert Heath - to assist him in technical development. The seeds for a method known as MIMO, or "multiple input, multiple output", were sown.
Paulraj's idea was to incorporate the space between antennae and receivers as part of the overall transferal equation - thinking about how buildings, ceilings, trees and any other objects influenced radio signals - and create a phenomenon called multipath propagation. By exploiting this, along with clever modulation techniques, he was able to incorporate at least two antennae and two receivers into wireless or Wi-Fi transmission. Instead of receiving two scrabbled signals, the receivers are able to recognise each individual signal thanks in part to the slightly different path it takes.
Without Paulraj's pioneering innovation, the increases in connectivity speed to which millions of people around the world have grown accustomed may not have been possible. MIMO is a key reason behind the increase in data transmission speeds by a factor of several hundred times between 2001 and 2006. And it continues to be employed in the next generations of wireless data standards.
Mobile phone networks, for instance, may never have evolved significantly past their analogue forebears. Fewer cutting-edge technology start-ups would have emerged. Mobile Cloud Computing would certainly be impossible. And, the digital era, ushered in by higher and higher bit rates, would have hit a wall.
"Multiple input, multiple output" functionality is such a central pillar of modern telecommunications that it is used in all new wireless systems. MIMO is essential for current 4G LTE networks and its importance will not diminish when 5G networks are rolled out in 2020. In 2015, network operators were spending EUR 5.1 billion (USD 5.6 billion) each quarter to provide customers with 4G LTE connectivity. By the time 5G coverage is introduced, it will already have attracted investment of EUR 4.6 billion, according to estimates. That amount is then likely to rise in subsequent years.
The economic success of Paulraj's innovation is attributable to the fact that the invention became a standard-essential patent. This led to others in the field contributing to the development of the standard as well.
However, the immediate economic impact of those areas of MIMO for which Paulraj holds patents is perhaps most apparent in the two start-ups he founded. In 1999, Paulraj, Gesbert and Heath founded Iospan Wireless to develop a specific type of MIMO product. The company was eventually acquired by Intel. In 2004, Paulraj co-founded a second company, Beceem Communications, which became a market leader in 4G wireless chip sets before its acquisition by Broadcom Corp. in 2010 for EUR 287 million (USD 316 million).
How it works
MIMO has given birth to a range of different technical incarnations, which makes it difficult to define simply. A core idea behind MIMO is space-time signal processing that takes into account the divergent paths that signals from two or more transmitting antennae will take, even if these antennae are very close to each other. If more than one receiving antenna is used to receive the signals, they can be broken down into their constituent parts.
A common application of the MIMO process starts with multiplexing, splitting the outgoing data stream at the link layer into frames that are then encoded, modulated and mapped to the two (or more) outgoing antenna. The radio waves are often polarised, shifting their amplitude to a pre-determined orientation so that the signals are mirrored (e.g. 45° and 135°).
This polarisation enables the antennae in the receiver to better determine from which outgoing antenna the signal originated and orient the data it is receiving at any particular moment within the entire incoming data stream.
Paulraj was born in southern India and joined the navy at the age of 15. He obtained an undergraduate degree in electrical engineering from the Indian Naval College of Engineering and went on to earn a PhD from the Indian Institute of Technology in 1973. By the end of his 30-year career in the service, he had achieved the rank of Commodore, the Indian Navy's fourth-highest rank. He moved to the US in 1991 to teach at Stanford University, where he is currently a professor emeritus of electrical engineering, but not until after he had founded three national-level laboratories at Indian universities and headed the development of one of the Indian military's most successful R&D projects - an anti-submarine SONAR system for the navy.
He is the recipient of more than two dozen awards, including two of the world's most prestigious honours for achievement in telecommunications: the IEEE Alexander Graham Bell Medal in 2011 and the Marconi Prize and Fellowship in 2014. He has also received the Padma Bhushan, one of India's highest civilian awards.
David Gesbert received his PhD from ENST, France, and was a post-doctoral researcher in Paulraj's group at Stanford University. He is currently a professor and head of the Communications Systems department at EURECOM, France.
Robert Heath was also awarded a PhD from Stanford University and is currently the Cullen Trust Endowed Professor at the University of Texas, Austin.
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Many of the inventors recognised by the European Patent Office with European Inventor Award have played key roles in the technology that has made this proliferation possible. They include Erik Dahlman and a team at Ericsson who helped develop LTE, Carles Puente and team who designed fractal antennae, Sophie Wilson, the inventor of ARM processors used in smart phones, and Japp Haartsen who invented Bluetooth.
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