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

Sarah Thomas
Prime Reading
Sarah Thomas, Director, Women in Comms
3/2/2015



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



On T-Mobile's VoWiFi progress: It is still pretty early days. We've seen better quality and better performance because the handoff is there. WiFi calling is used by customers that see benefit from it, and we have over 7 million customers using it, and they are quite happy with it, but we never expect all our customers to use it. But for the people who use it, it's very successful. It's something that's a good part of our solution. It isn't one of these things where we have to push everyone to it for capacity. It's for the customer, not us. (See Sprint, T-Mobile Test Ruckus's Refined VoWiFi and T-Mobile Turns Up VoLTE-to-WiFi Handoff.)

On ending the map wars: Outside of cities, we see the low-band solution as really the key to end the map wars and get out there and show people we have coverage everywhere. Verizon always puts up maps to show they cover North Dakota, South Dakota, Montana, which are beautiful states, of course, but not a lot of people are there. It looks great on TV, but it doesn't make a huge difference to people. That said, we are going to close that gap with 700MHz and expect to have a competitive map towards the end of the year, because we can with our low-band.

On 5G: The whole 5G thing is a name game thing. The official answer is we're working with industry groups on 5G. It'll take a long time. We'll be part of the conversation. It will be high data speeds and high capacity and small cells and macro cells and HetNet combos. My personal perspective -- it sort of seems to be this grab bag of all the great things being built on top of LTE. Just add another "G" to it. In my view, this is just the logical next step of what LTE should be. At some point, people will glue them all together and say, "it's something more; it's 5G."

On the 4G debate of the past: The more interesting thing is the fact that many years ago there was a big debate about what 4G was. The first company with 4G was Sprint with WiMax. People were really excited about it. Everyone thought it was cutting edge. Everyone thought it was leading. What you found was they adopted the wrong technology -- it was limited, the best speeds were pretty bad. Our UMTS network started outperforming that. Our UMTS was 4G and everyone said 'no, not true.' It's not fair -- our performance is better, but they get to be 4G and we donít. Then AT&T said the same thing, and then everyone did and they forgot. It's a name game in my view. The bigger thing -- and LAA is a good example of this -- is taking good ideas and driving them to implementation because it's the right thing to do. We're going to make it happen.

On RCS: I think we're excited about continuing to build great things on top of our LTE network. We have a very solid IMS infrastructure behind our LTE network that allows us to implement things like WiFi calling with mobility. It allowed us to do VoLTE. We'll do things like RCS, video calling and other things out there where we can leverage the strengths of our LTE network and IMS network and really provide services and solutions that start to make people see the next generation. It's not just about speed, but flexibility and voice and IP convergence and things people will get excited about.

RCS is soon, very soon. VoLTE was the baseline on that and was the most difficult. We worked hard to move it forward. We're taking those learnings for RCS and video calling and similar services. Video calling will be built on top of VoLTE. We're leveraging what we've learned and building on top of it. You cannot do that unless that foundation is rock solid. That's what we've been focused on.

On T-Mobile's VoLTE progress: We are around 10-plus percent of calls on VoLTE. It's slowly growing and it will accelerate quickly. It's mostly about handset adoption -- getting them all enabled. Our launch with the iPhone was a big help. Our work with Samsung on the Galaxy line up is also helpful.

On the potential of deals with Dish and Google: Nothing I can speak to. [Ed note: Hey, we had to ask!] (See T-Mobile: Google & Dish Could Be 'Interesting' Partners.)

On what's next: In general, we've been really happy with our data strong network and will continue to grow on that with expansion of LTE in our low-band portfolio. By end of the year, we'll have a "no-regrets network" that's comparable to everyone else. It's a battle out there, and we think we'll win.

On Uncarrier 9.0: It'll be someday soon. We don't stop; we don't slow down; we just keep going.

ó Sarah Thomas, Circle me on Google+ Follow me on TwitterVisit my LinkedIn profile, Editorial Operations Director, Light Reading

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