Breaking down the barriers of full duplex radio

Published by CW (Cambridge Wireless)

Self-interference cancellation techniques advanced enough to make full duplex a reality according to speakers at CW Radio SIG meeting in Bristol

“We can consider the problem of self-interference cancellation as solved,” said David Lister, Research Manager at Vodafone UK, speaking at CW Radio SIG meeting in Bristol yesterday. “Now is the time to consider system requirements and assess the use cases. There are still major challenges to overcome when applying full duplex to systems with multiple base stations and terminals.”

Common consensus on the day was that a drastic shift in architecture was required to produce new duplexing techniques that can integrate the technology into handheld devices at an affordable cost. This issue was touched upon in the presentation from Samantha Caporal del Barrio, Industrial Post-Doc from Aalborg University and WiSpry. “Along with the standardisation of LTE and LTE-A came a need for increasing the antenna bandwidth as well as the number of front-end filters on the mobile devices. The two main issues this created are the space available inside the mobile platform and its cost,” said Caporal del Barrio, who suggested the use of two frequency reconfigurable narrow-band antennas as an encouraging alternative.Splitting the transmitting from the receiving chains allows us to considerably reduce the component count, helping with both cost and real estate.”

Leo Laughlin, PhD student at the University of Bristol EPSRC Centre for Doctoral Training (CDT) in Communications, provided delegates with a vision of a future multi – mode, multi-band cellular handset. "Novel duplexing techniques will be vital, not only to reduce cost but also to enable roaming in 4G devices and potentially double the spectral efficiency in future systems,” said Laughlin, who presented the University of Bristol’s prototype full duplex transceiver at the event, capable of simultaneous transmission and reception from a single antenna. “Combining electrical balance isolation with active radio frequency cancellation can suppress self-interference by a factor of over 100 million using low cost small form factor technologies and takes us one step closer to bringing this technology into a handheld product,” added Laughlin.

Delegates were also offered an insight into Air Division Duplexing by Geoff Carey, Director of MIMOtech, a technique that has already enabled the company to launch a range of ultra-high capacity radios in the microwave backhaul arena. “The technology combines full duplex transmission and MIMO to double transmission capacity for microwave backhaul,” said Carey, who believes Air Division Duplexing is on the fast track to early adoption. “The hunger for increased backhaul throughput by operators coupled with advances in technology in other key RF areas should accelerate the acceptance process considerably.”

The event held at the University of Bristol’s School of Chemistry was the latest meeting of the Cambridge Wireless Radio SIG, sponsored by Rohde and Schwarz. To view copies of presentations posted after the event please visit the Cambridge Wireless resources page.

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