Engineers from the Universities of Bristol and Lund have partnered 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.

The initial 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.

Recently, the research team also assessed the performance of a 128-element massive MIMO system operating at 3.5GHz and the trials indicated that this technology could offer spectrum efficiency figures in excess of 100bits/s/Hz, improving upon the capacity of today’s long term evolution (LTE) systems by a factor of 10.

 
See also: Massive MIMO trials show 100bits/s/Hz efficiency »