Google Sees 3.5 GHz, Much Greater Spectrum Sharing as Key to 5G

The 3.5 GHz Citizens Broadband Radio Service Band has the potential to become a key band for 5G, Preston Marshall, principal wireless architect at Google, said at the DC5G conference Wednesday. If the FCC allows smaller license sizes, hotels like the Renaissance Washington, where the event took place, can set up their own networks independent of the carriers, Marshall said. “We’ve never had that.”

Because of the poor propagation characteristics of the high-frequency spectrum that will be used for 5G, Marshall said he questions whether all the carriers will be able to separately install all the facilities they will need, so sharing is critical. Marshall said in a large room like the meeting room where he was speaking, each carrier would have to install at least 15 access points. That would mean four carriers “tearing the walls down to pull exclusive fiber through,” he said. “It doesn’t make a lot of sense.”

The FCC is looking at an NPRM that would rewrite the rules for the CBRS band, changing the rules for the priority access licenses (PALs), one of the tiers, which critics say would make the band less viable for general access use (see 1710030059). Marshall told us he couldn’t comment on the NPRM, and the filings Google made at the FCC speak for themselves. If he said anything more, “my lawyers will fire me,” he joked.

Because of the poor coverage of cellular networks, consumers have had to look elsewhere, Marshall said. “Wi-Fi responded,” he said. “Wi-Fi has become a dominant model.” Wi-Fi is a sharing model and the 3.5 GHz band picks up on that, creating a three-tier sharing system, Marshall said. “Different access rights within the same band is what I believe can fundamentally change 5G.”

The nature of wireless will be thoroughly different with 5G, but 4G has been a kind of lab, Marshall said. With 4G there was very poor coverage indoors and a lack of penetration, while 5G will mean better connectivity, he said. One problem with the cellular model is that it was built for outdoor use, he said. It works "OK" with low-band spectrum, but the coverage deteriorates in higher spectrum bands. Indoors “is where the action is,” he said.

Other speakers agreed 5G is a necessary next step to keep up with demands of users. “The internet was not designed for what we’re using it for today,” said Phill Lawson-Shanks, chief architect at technology company EdgeConnex. “The structure, the tromboning of traffic … a lot of that baseline technology has to move as close as possible” to the device and the antenna, he said. “Given the ability to put infrastructure as close as possible to the antennas, you can then start pushing down different forms of technology.”

Technology has moved at a rate that’s hard to comprehend, Lawson-Shanks said. “I saw a report saying if you were to build just the iPhone … with 1970s technology, basically it would cover the whole of San Francisco … and still wouldn’t have a camera,” he said.

Rikin Thakker, lecturer in the University of Maryland telecommunications program, said Marshall’s vision of 15 access points in a single, large conference room should make everyone nervous. “How is going to be possible if you’re going to have 15 small cells from each carrier in this room? It is actually a very scary reality that we need to address immediately.” Thakker agreed sharing the infrastructure will be critical. A recent Accenture paper estimated investment for 5G will require $275 billion over seven years, he said. “Where are we going to get that money?”