Doubling radio frequency data capacity

A nanoscale IC enables simultaneous transmission and reception at the same frequency

A team of researchers at Columbia University in the US have invented a technology - full-duplex radio integrated circuits - that can be implemented in nanoscale CMOS to enable simultaneous transmission and reception at the same frequency in a wireless radio.

Up to now, this has been thought to be impossible: transmitters and receivers either work at different times or at the same time but at different frequencies.

The Columbia team, led by Electrical Engineering Associate Professor Harish Krishnaswamy, claims to be the first to demonstrate an IC that can accomplish this.

“This is a game changer,” said Krishnaswamy. “By leveraging our new technology, networks can effectively double the frequency spectrum resources available for devices like smartphones and tablets.”

In the era of big data, the current frequency spectrum crisis is one of the biggest challenges researchers are grappling with and it is clear that today’s wireless networks will not be able to support tomorrow’s data deluge.

Today’s standards, such as 4G/LTE, already support 40 different frequency bands, and there is no space left at radio frequencies for expansion. At the same time, the grand challenge of the next-generation 5G network is to increase the data capacity by 1000 times.

So the ability to have a transmitter and receiver re-use the same frequency has the potential to immediately double the data capacity of today’s networks.

Krishnaswamy notes that other research groups and start-up companies have demonstrated the theoretical feasibility of simultaneous transmission and reception at the same frequency, but no-one has yet been able to build tiny nanoscale ICs with this capability.

The CoSMIC (Columbia high-Speed and Mm-wave IC) Lab full-duplex transceiver IC that can be implemented in nanoscale CMOS to enable simultaneous transmission and reception at the same frequency. Credit: Jin Zhou and Harish Krishnaswamy, Columbia Engineering.

“Our work is the first to demonstrate an IC that can receive and transmit simultaneously,” he said. “Doing this in an IC is critical if we are to have widespread impact and bring this functionality to handheld devices such as cellular handsets, mobile devices such as tablets for Wi-Fi, and in cellular and Wi-Fi base stations to support full duplex communications.”

The biggest challenge the team faced with full duplex was cancelling the transmitter’s echo.

“Transmitter echo or ‘self-interference’ cancellation has been a fundamental challenge, especially when performed in a tiny nanoscale IC, and we have found a way to solve that challenge,” explained Jin Zhou, Krishnaswamy’s PhD student and the paper’s lead author.

Krishnaswamy and Zhou plan next to test a number of full-duplex nodes to understand what the gains are at the network level.

The researchers presented their work at the International Solid-State Circuits Conference (ISSCC) in San Francisco on 25 February. The work was funded by the DARPA RF-FPGA program.