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Q&A: The Castle in T-Mobile's LTE Network

Sarah Thomas

T-Mobile is the scrappy comeback kid of the US wireless industry. It's turned around its network and its image in near-record time over the past few years, and it's an evolution -- or revolution -- the company has vowed to continue until becoming the market leader.

For every promise T-Mobile US Inc. CEO John Legere has made the industry, whether it be slashing service rates, shaking up handset pricing or improving international roaming, the carrier's CTO office has to be there to make sure it can back up his often audacious and always colorful claims.

Grant Castle is the vice president of engineering and quality assurance on CTO Neville Ray's team, responsible for much of the carrier's network upgrades. Light Reading caught up with Castle ahead of Mobile World Congress to share an update on the carrier's plans for small cells, LTE-U, rich communication services (RCS) and much more.

Grant Castle,T-Mobile's VP of Engineering
Castle is on T-Mobile CTO Neville Ray's team, focused  on improving the customer connection experience.
Castle is on T-Mobile CTO Neville Ray's team, focused
on improving the customer connection experience.

The following is a lightly edited transcript of Light Reading's conversation with Castle.

On the key to T-Mobile's network evolution: We have a strong LTE network that we've been building very quickly over the past couple of years. The key to our LTE plans has been the fact that we have a very solid mid-band spectrum portfolio that -- thanks to AT&T and others -- we've been able to centralize and aggregate in alignment with LTE. Since AWS has become the de facto spectrum band, it aligns well with our portfolio.

We also have the advantage of an advanced cell site infrastructure in cities since we hadn't historically had low band. Over the past 10 to 15 years, we've been constantly increasing the density of our network and focusing on getting the right coverage and capacity in all the major cities. We can leverage the spectrum density we have and put the pedal to the medal on LTE deployments. It lets us lean into LTE and put a lot of resources behind it to yield the fastest LTE network in the US. We put the sites and spectrum where it matters -- where people and usage is. We are in a good position. We do have a speed claim, which is great, but it's also a reflection of our capacity. We just flat-out have more capacity on our LTE network because of our site density and spectrum holdings.

It lets us be aggressive in pricing and service. We're over-delivering on quality even though a lot of people think we're a trade-off on quality. The vast majority of our customers spend most time in areas with lots of speed.

On buying up spectrum: We believe we acquired spectrum smartly -- paid reasonable prices for important areas -- nothing silly in bidding. We're filling in small holes in our mid-band portfolio and expanding our low-band portfolio, acquiring licenses in other areas. We have been amassing a spectrum portfolio that makes sense for us. (See FCC's Monster Auction Ends at $45B in Bids and T-Mobile Boss Asks Consumers to Pressure FCC on Low-Band.)

On small cells: We've been testing technology like small cells. We will continue to do work there, but don't think our network is screaming for small cells. We like our site density. There is a niche solution for small cells in some areas, but it's definitely not all in what we need to be successful. That's how we see them at this point.

On LTE-Unlicensed: The advantages of the unlicensed LTE stuff is really again just a spectrum play. We see areas where we can take existing LTE sites -- generally in more urban areas with a smaller cell radius and more density -- and add LTE on top of that as an additional spectrum that can add speed and capacity, but not something you can fully count on. Given the vast amount of unlicensed spectrum and the way we think we can play it smartly, we think we can get to a position where we get a lot of benefit from it, where it makes sense, but not spending lots of money on spectrum acquisition. It will be pretty niche, not deployed across the US. (See T-Mobile Gets Small & Unlicensed With Nokia.)

On why T-Mobile isn't waiting for LTE-U standardization: We are very impatient. We roll out as fast as we can; as quickly as we can. This is a case where the right thing to do is move the technology forward, like with VoLTE. We are going to continue to push the tech envelope because we need to. We take the things that advantage us and push them forward in the industry. We did this as well with voice-over WiFi -- been doing that for a decade. It was the right thing to do. We've been there many times before.

Next page: Castle on VoWiFi, VoLTE, RCS, 5G and more

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3/13/2015 | 8:04:04 PM
Re: the network man
'I'm curious to see what it does with RCS too"

This. Video calls are "neat" but I'm not so sure users are really there for wanting to place video calls all the time (esp given how popular texting still is). Perhaps video texting might become more of a thing? But then the low latency aspects are not really necessary.

Is there a user-driven demand for RCS apps? What is it?

3/2/2015 | 11:54:59 AM
the network man
It was great to get Castle's perspective on how far T-Mobile has come and what else is on the roadmap. He has a tough job, having had to launch and update the network so fast in the last few years, and there's still a lot of work to be done as it looks to expand its low-band spectrum.

I'm curious to see what it does with RCS too, since Castle says it's coming "very, very soon." The launched VoLTE nationwide early on. I imagine RCS will follow the same trajectory.
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