British-Swedish research team breaks spectrum efficiency record

A team of researchers from the University of Bristol and Sweden’s University of Lund have demonstrated a massive antenna system that can offer a 12-fold increase in spectrum efficiency when compared with the cellular technology currently in use in 4G networks.

Massive antenna, or multiple input multiple output (Mimo), is a system that combines multiple antennae at the transmitter and destination to minimise errors and boost data speed.

It is currently well-used in Wi-Fi hardware and 4G networks – usually involving up to four antennae – but the Bristol-Lund project, which used a National Instruments (NI) prototyping platform based on LabView software and PXI hardware, deployed 128 antennae.

The demonstration took place at Bristol’s Merchant Venturers Building. It operated at a carrier frequency of 3.5GHz and supported simultaneous wireless connectivity of up to 12 single antenna clients, with each client sharing a common 20MHz radio channel, while digital signal processing algorithms unravelled individual data streams in the space domain seen by the array.

It achieved an unprecedented bandwidth efficiency of 79.4 bits per second per hertz (bps/Hz), equalling a sum rate throughput of 1.59Gbps in a 20MHz channel.

Lund University professor of radio systems Ove Edfors said: “We see massive Mimo as the most promising 5G technology. We have pushed it forward together with partners in Bristol and in our EU project Mammoet [Massive Mimo for efficient transmission].”

“Massive Mimo is one of four core activities in ‘5G and beyond’ wireless research at Bristol,” added Mark Beach, professor of radio systems engineering at Bristol University’s Department of Electrical and Electronic Engineering.

“This demonstration was made possible by the cohort training offered in our CDT [Centre for Doctoral Training] in Communications. The CDT gives Bristol a unique edge to conduct activities at scale.”

The demo brought together five Bristol-based and seven Lund-based PhD students, and eleven academic supervisors. The hardware in use was provided through the Bristol is Open smart city programme, and a similar programme running in Lund.

“This is truly outstanding work putting Bristol at the forefront of 5G wireless connectivity,” said Paul Wilson, managing director of Bristol is Open. “We are looking forward to moving this facility outdoors in late 2016 as part of the BIO Harbourside deployment.”