AT&T Waltzes Towards Massive MIMO
AT&T says that it has been testing "massive MIMO" with Shentel and startup Blue Danube. (See AT&T, Shentel Test Blue Danube MIMO.)
The tests used Blue Danube's 96-element BeamCraft500 active antenna, and delivered up to five times the throughput of standard LTE networks, the startup said. The test is significant because it was using dual-band Frequency Division Duplex (FDD) LTE spectrum.
Previously Massive MIMO has been trialed in high-frequency single-band Time Division Duplex (TDD) spectrum. It is easier to build large multiple input and output antenna arrays in TDD at higher frequencies because the individual elements are smaller.
AT&T Inc. (NYSE: T) is an investor in Blue Danube Systems . The operator has also made clear it wants to upgrade its network to deliver 1 Gbit/s download speeds in "some areas" in 2017. (See AT&T Preps 4.5G Cities, 5G Testbeds.)
All of this, however, begs the question: How many antenna elements does an array need to be called "Massive MIMO" anyway?
I checked with Heavy Reading's Principal Analyst Gabriel Brown and he said that there is no formal definition. Massive can apparently be defined as tens, hundreds or thousands of antenna elements.
"By Massive MIMO, I mean 64 transmitters and 64 receivers," Nokia's VP of Networks Marketing Phil Twist told Light Reading recently. That's 128 antenna elements if you're counting. (See So What Is 4.9G Anyway?)
Still, a 96-element antenna will boost performance on these networks. 8 Transmitters and 8 receivers is currently cutting edge for FDD LTE networks in the US.
— Dan Jones, Mobile Editor, Light Reading