sprintThere’s a lot of talk about using massive MIMO antennas to boost mobile network performance these days. But according to Sprint CTO John Saw, “not all massive MIMO is created equal.”

At an investor conference yesterday, Saw said Sprint massive MIMO will have an advantage because it will operate in the 2.5 GHz band, because its MIMO antennas will have more elements than those of some other carriers, and because the company uses time division duplexing (TD-LTE) rather than frequency division duplexing (FDD-LTE) for its LTE network.

Sprint Massive MIMO
“Massive MIMO doesn’t work well in low-band spectrum,” said Saw. Massive MIMO equipment operating in lower frequency bands would need to be quite large, making it difficult to install on existing cell towers, he said. “2.5 GHz or higher bands is where it makes sense,” he commented.

Sprint plans to use 128-element MIMO antennas, which should provide better performance than the four- or eight-element antennas that are used in a “traditional build,” Saw said.

What Sprint will be deploying is a single box that includes a radio head, the 128-element MIMO antenna and coax. Installation will be simple, according to Saw. Technicians will be taking down three separate elements and replacing them with the single box.

The new equipment will yield a four- to 10-time capacity improvement over existing LTE equipment, Saw said.

John Saw Sprint

John Saw

Saw also argued that Sprint’s use of TD-LTE provides greater “certainty” because, unlike with FDD-LTE, both transmit and receive functions occur on the same channels. Sprint is the only U.S. carrier using TD-LTE. Saw noted, though, that all carriers will use time division duplexing for 5G.

Finally, Saw noted that Sprint will be able to split a node in two to simultaneously support LTE and, eventually, 5G.  The carrier said earlier this year that it will be able to use a software upgrade to update massive MIMO equipment to support 5G as well as LTE service. At that time the carrier said it plans to deploy thousands of massive MIMO antennas this year and that the antennas will support the company’s planned 5G launch in several markets in the first half of 2019.

Subsequently, the company announced plans to merge with T-Mobile but Saw said those plans have not caused Sprint to slow its network investment – an important revelation, considering that the merger does not yet have regulatory approval.

Neverthless, Saw noted that “Now is the time to look at the synergy of building one 5G network.”

T-Mobile and Sprint appear to be serious – finally — about their on again/ off again merger plans, as a 600-page filing with the FCC this week revealed.

Asked about whether there are any key applications that will require 5G connectivity, Saw commented that Uber and other companies were “built on the back of LTE,” but no one foresaw those companies. He believes 5G also will spur the development of new applications, perhaps in the healthcare area, that no one yet has thought of.

Saw made his comments at Wells Fargo Securities 5G Forum, which was also webcast.