Engineers from the Universities of Bristol and Lund have teamed up with National Instruments (NI) to demonstrate how a massive antenna system can offer a 12-fold increase in spectrum efficiency compared with current 4G cellular technology.

Multiple antenna technology, referred to as MIMO, is already used in many Wi-Fi routers and 4G cellular phone systems. Normally this involves up to four antennas at a base station. Using a flexible prototyping platform from NI based on LabVIEW system design software and PXI hardware, the Bristol configuration implements Massive MIMO, where 128 antennas are deployed at the base station.

The hardware behind this demonstration was provided to Bristol University as part of the Bristol Is Open programmable city infrastructure. Lund University has a similar set-up, the LuMaMi testbed, enabling researchers at both sites to work in parallel with their development.

Bristol’s Massive MIMO system used for the demo operates at a carrier frequency of 3.5GHz and supports simultaneous wireless connectivity to up to 12 single antenna clients. Each client shares a common 20MHz radio channel. Complex digital signal processing algorithms unravel the individual data streams in the space domain seen by the antenna array.

Bristol Massive MIMO 01 (cr) Figure 1: The University of Bristol and Lund University implemented the world's first 128-antenna, real-time massive MIMO testbed, which was used to set two consecutive world records in wireless spectral efficiency. (Source: National Instruments)

The Massive MIMO demonstration was conducted in the atrium of Bristol’s Merchant Venturers Building and achieved an unprecedented bandwidth efficiency of 79.4bit/s/Hz. This equates to a sum rate throughput of 1.59Gbit/s in a 20MHz channel.