Photo by Diana Goovaerts/Wireless Week. T-MObile CTO Neville Ray speaks during Ericsson's press briefing Monday morning.

T-Mobile CTO Neville Ray made a guest appearance at Ericsson’s media briefing Monday morning, during which he shared his thoughts on 5G, the future of LTE, and T-Mobile’s work with LTE in unlicensed spectrum.

During the session and in a chat with reporters afterward, Ray explained T-Mobile’s vision for 5G isn’t just about next generation technology, but also about boosting LTE capabilities to make the leap to 5G more of a staircase climb.

“When we move to 5G, I don’t want to have a 2G and a 3G network behind me,” Ray said. “I am retiring legacy technologies at a furious pace … LTE is where we really learn our trade and really build all the foundation blocks that are necessary for a 5G future.”

According to Ray, two-thirds of T-Mobile customers are now on Voice-over-LTE (VoLTE) and 93 percent of its data traffic also flows over LTE. The Un-carrier is driving very hard toward an all-LTE network, Ray said, but noted progress has been hampered by the legacy handset upgrade rate.

When it comes, Ray indicated a 5G roll out will likely start in urban markets first through small cell densification, but said T-Mobile is still working to address the challenge of bringing 5G to more rural markets. The Un-carrier isn’t currently toying around with sub-6 GHz spectrum for 5G, which means the propagation issues inherent in higher bands must be solved.

“The problem will be in those lower bands, and anything sub-6 GHz you can’t get the huge volume of spectrum you need to support 10 Gbps speeds,” he said. “So that’s going to be a continued challenge for a period of time … it will be tough in suburban and rural areas.”

However, one way to help avoid a service drop off outside of 5G coverage areas is to enhance the LTE network to gigabit speeds, he said.

In the quest to meet 1 Gbps, Ray reiterated T-Mobile’s previous announcement that LTE-U is on the way, with the first compatible handset expected in the spring. Ray said the geographic spread on LTE-U will be limited at first, but added the Un-carrier is also planning to roll out License Assisted Access (LAA) technology later this year.

“LTE-U will just be 20 MHz supplemental downlink. That’s 20 MHz, that’s a lot of spectrum,” Ray reported, specifying that it will be unlicensed spectrum in the 5 GHz band. “LTE actually looks pretty nice compared to 5 GHz WiFi. So you can do a lot of damage with 5 GHz LTE in terms of coverage and propagation.”

Ray noted the unlicensed spectrum story is one of hundreds of megahertz of open spectrum – though not all readily accessible – that could provide a medium for “some 5G activity.” He said T-Mobile is “excited” about the prospect.

One thing Ray wasn’t jazzed about, however, was Verizon’s focus on fixed wireless. According to Ray, fixed wireless is a “fringe” use case and argued that “nobody is going to displace the cable guy with 28 GHz LTE.”

“I think it’s a valuable use case, but does it excite me? Hell no,” Ray said. “If that’s all we’re doing with 5G is displacing fixed broadband then we should pack up our bags and go home. The piece that’s exciting about 5G is how are we going to revolutionize the consumer experience. That’s what this industry is really about and that will drive the next fundamental wave of growth.”

Ericsson, which is partnering with Verizon on the fixed 5G trials, did have a counter for that point, though. CEO Borje Ekholm said the lessons learned in the fixed wireless trial will help determine how the 5G core network is built.