AT&T pushes Massive MIMO into FDD-LTE via Blue Danube investment

Massive MIMO is at the heart of many 5G trials (see separate item), but it is starting to become an option for a few extremely capacity-constrained operators, even in LTE networks. The early moves have mainly been Asia-focused – Huawei and ZTE supporting dense hotzone trials or deployments by MNOs like Softbank or China Mobile.

But last week a lesser known vendor, Blue Danube Systems, said it had completed the first commercial trials of its Massive MIMO technology in with AT&T (one of its investors) and Virginia-based regional carrier Shentel.

The Silicon Valley start-up has its own approach to advanced 3D beamforming, to be used in conjunction with increasingly large MIMO antenna arrays to mitigate interference and boost capacity and cell edge data rates.

In particular, the trial was interesting because the 96-element BeamCraft500 active antenna was running in dual-band FDD spectrum. Most Massive MIMO trials have taken place in high frequency single-band TDD spectrum because this requires smaller elements, making it easier to build large arrays. However, vendors are starting to push the technology into the more mainstream sub-3 GHz FDD spectrum – China Unicom recently talked about FDD Massive MIMO trials with both Huawei and ZTE.

Joe Madden, founder of mobile infrastructure analyst firm Mobile Experts, commented: “Instead of waiting for 5G, mobile operators are upgrading thousands of TD-LTE base stations with Massive MIMO this year,. It’s an exciting development which, as it gains momentum, may be able to leap into the FDD market as well. Blue Danube’s recent FDD field trial results using simple modules are very promising, and represent a big step toward cost effective FDD and 5G solutions.”

The North American trials supported over 10TB of data over a three-month period. After its BeamCraft 500 unit was retrofitted to existing LTE sites, Blue Danube says it achieved as much as 500% increase in throughput in high traffic areas using the same transmitting power as the legacy installation.

A second phase of trials is now ongoing to test additional operational modes and traffic scenarios.

The two operators involved in the trials talked up the results.

“AT&T is committed to enabling next generation mobile experiences by exploring leading edge capabilities,” said Tom Keathley, AT&T’s VP of wireless network architecture and design, in a statement. “The work we have done with Blue Danube to evaluate their beamforming technology in our live network supports this objective.”

“The versatility of this advanced antenna system has provided dramatic performance improvement in our commercial network by dynamically increasing RF energy in problem areas without impacting neighboring sites,” said Willy Pirtle, SVP of wireless for Shentel.

Blue Danube CEO Mark Pinto likes to compare his firm’s synchronized transmitter arrays with dozens of people throwing pebbles in a pond – the pebbles must be thrown at precisely the right time and place to create a big splash rather than a random assortment of small waves colliding with one other.

The company said: “Massive MIMO offers significant gains in wireless data rates and link reliability, allowing for data consumption from more users in a dense area without consuming any more radio spectrum or causing interference.”

The 96-element BeamCraft 500 active antenna can deliver 160W of transmit power for a Massive MIMO system. It is based on Blue Danube’s underlying High Definition Active Antenna System (HDAAS) technology, allowing it to focus signal energy where it is needed to target high traffic areas and minimize interference zones.

Blue Danube is also developing additional HDAAS products for additional spectrum bands and TDD LTE operation to support several trials in Europe, Australia and North America in the first half of 2017.

“Mobile carriers are looking for innovative and cost-effective ways to improve network capacity and Blue Danube’s BeamCraft™ 500 is the first product designed to provide operators a low friction upgrade at existing sites targeting lowest total cost of ownership for high capacity,” said Earl Lum, president of EJL Wireless Research. “The compact form factor for a 160W system with no fans and use of existing CPRI to the eNodeB makes the solution very attractive. Results from first commercial trials are very promising and validate efficiency and simplicity of the system”.