Without Paulraj and his team pioneering MIMO and dramatically improving the performance of wireless networks, the fast Internet connections to which millions of people around the world have grown accustomed may never have materialised.
With the increasing internet users through smartphones and wireless devices, the demand for network providers to deliver faster, more reliable connections is on a rise. However, the problem with the wireless spectrum is that it is limited. Bandwidth must be shared between those surfing the web, watching TV broadcasts, and listening to podcasts and radio. Bandwidth is precious – and it’s expensive too. So when Arogyaswami Paulraj (72), an electrical engineer from India who moved to the United States in 1991 to teach at Stanford University, came up with a way to cram more digital data into the radio waves that make up the wireless spectrum, it was a boon for both the network providers and their customers. Dr Paulraj was supported by two of his post-doctoral students – David Gesbert and Robert Heath. The team helped transform Paulraj’s ideas into one of wireless communications’ most successful and effective technologies.
For this achievement, the European Patent Office (EPO) has named Arogyaswami Paulraj and his team as one of three finalists for the European Inventor Award 2016 in the category “Non-European countries”. The EPO will announce the winners of the 11th edition of its annual innovation prize at a ceremony in Lisbon on 9 June.
“In today’s interconnected world, wireless connections have become a fundamental part of everyday life for billions of people across the world,” said EPO President Benoît Battistelli announcing the European Inventor Award 2016 finalists. “The technology developed by Arogyaswami Paulraj and his team has contributed significantly to faster wireless data transmission, one of the cornerstones of the digital era. In doing so they have helped us all connect faster.”
Multiple input, multiple output: The path-breaking innovation
The idea was simple, yet inventive; in order for devices at both ends of a wireless link to transmit data at a faster rate, additional antennae are required. This technique is known as spatial multiplexing, but it is more commonly referred to as MIMO, for “multiple input, multiple output”. There was only one problem; one that had haunted radio communications since its inception: multipath propagation. Radio signals tend to bound around before reaching their target and when two discrete singles are transmitted over the same frequency, it is nearly impossible to distinguish them from each other using one antenna.
By adding up an additional receiving antenna and rethinking multipath propagation in order to use the distortions it produces to help distinguish between signal waves, Paulraj and his team were not only able to improve the bit rate, or connection speed – they also enlarged signal coverage areas. What’s more: MIMO was able to achieve a higher rate of data transmission within the same channel bandwidth (frequency spectrum), meaning there was no need for extra power or coveted bandwidth.
“Once you have a two-by-two system [four antennae] you get twice the throughput,” explains Paulraj. “A four-by-four system creates four times the throughput. In cellular communications or in Wi-Fi, where spectrum is very, very limited, if you have multiple antennae you can increase the speed of the link.”
Ahead of his time
Serving the Indian Navy for 30 years and earning the rank of Commodore, Paulraj developed the idea for MIMO in 1992 while at Stanford University, where he is now a professor emeritus of electrical engineering. The idea behind MIMO sprouted when Paulraj set out to find a method for the US Airforce reconnaissance plane to listen in on multiple signals without interference – the solution, a multi-antenna array. After modifying this concept for wireless communications, he was awarded his first MIMO-related patent in 1994, but it would take nearly a decade for the first commercial applications of the technology to emerge. This delay was largely attributable to the fact that US wireless networks were still mostly analogue. Paulraj’s technology required digital networks to function, and a wholesale infrastructure upgrade was not carried out until the early 2000s. Today, however, MIMO is ubiquitous.
The world as we know it
Mobile phone networks may never have evolved past their analogue for bearers; fewer cutting-edge start-ups would have emerged; and cloud computing would certainly never have been possible. Indeed, bit rates, the lifeblood of the digital era, would have hit a wall somewhere along the line. But MIMO does exist, and service providers are investing heavily in network infrastructures to bring their customers even faster connections. In fact, in 2015, companies were spending EUR 5.1 billion (USD 5.6 billion) every 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, and that amount is only expected to rise in subsequent years.