T-Mobile, Nokia executives discuss upcoming LAA deployments in 5 GHz spectrum

Corker, left, and Ray

with Neville Ray, EVP and CTO of T-Mobile US, and Ricky Corker, EVP of North American markets for Nokia Networks

With licensed spectrum becoming a scarce and expensive resource, operators such as T-Mobile US (NYSE:TMUS) are now looking at unlicensed spectrum as a new frontier for deploying LTE.

At last week's Mobile World Congress conference in Barcelona, Spain, T-Mobile announced that it will deploy Licensed Assisted Access (LAA) in the 5 GHz unlicensed spectrum band in 2016. The operator, which is working with multiple vendors, also demonstrated LAA capabilities at the show with Nokia Networks. Sue Marek, editor in chief of FierceWireless, spoke with T-Mobile CTO Neville Ray and Ricky Corker, EVP of North American markets for Nokia Networks, about the growing momentum around LAA in the United States.

FierceWireless: T-Mobile just announced plans to deploy LTE in unlicensed spectrum and have it commercially ready by 2016.  Why unlicensed spectrum?

Ray: The technical specifics are Licensed Assisted Access (LAA), which is leveraging LTE in the unlicensed space and combining it with the underlying LTE network. It's using downlink carrier aggregation, which means you have LTE in the 5 GHz band and supplemental downlink coming down and adding to the underlying LTE network.

FierceWireless: When do you expect LAA to be a reality?

Ray: All of the key drivers and momentum in the industry are around Licensed Assisted Access. It will come through this year and into next. Vendor collaboration and operator collaboration in U.S. is already formidable. T-Mobile and Verizon are leading the way. Both operators have talked about it at the [Consumer Electronics Show]. Nokia is key partner for us. Qualcomm is also in the mix and handset vendors are stepping up.

FierceWireless: When do you expect LAA-compatible handsets to be available?  

Ray: We are pushing partners hard to make this happen. We don't have commitments yet but I believe we will have handsets available for testing this year. That means commercialization of capability in 2016.

FierceWireless: Is LAA always going to be deployed in 5 GHz or are other unlicensed bands also going to be used?

Corker: The 5 GHz band is the most prominent band but 3.5 GHz band can be adapted.  

Ray: The 5 GHz band is clearly where there is the most energy, and that's where the first solutions will be. But any unlicensed band is open to LTE.

FierceWireless: Some members of the Wi-Fi community are still concerned about possible interference from LTE. Is this a valid concern?

Corker: Part of the capability of LAA is being able to mitigate the interference issues by having software that allows us to move traffic to channels that don't interfere with Wi-Fi. We can demonstrate that it coexists very well. If you do pure LTE with Wi-Fi in unlicensed it will interfere. If we go to a channel occupied by Wi-Fi, there will be interference, our software will move it to a new channel. Because 5 GHz is so big a band we can find channels that aren't occupied.

Ray: Co-existence with Wi-Fi is important. We are making sure we are being a good neighbor to existing Wi-Fi.    

Corker: LTE and W-Fi typically have similar throughput and capacity. If someone is using an LTE device standalone, I have same throughput as Wi-Fi.  But if you have multiple users on Wi-Fi, you will find that the capacity drops. But with LTE there is an advantage because we have a scheduling technique so that experience is better. 

FierceWireless: Why is LAA so much better than offloading?

Corker: The system capacity is much less with LTE than with just putting more Wi-Fi in that spectrum.

Ray: It's more efficient use of the spectrum. You can get more capacity per user and better speeds. The other thing is propagation and strength of the LTE signal bearer in 5 GHz is much better than Wi-Fi.

Our early deployment of LAA won't be in big macrocells but if you think about the commercial enterprise where there may be very under-utilized 5 GHz Wi-Fi, there could be more speed capacity per user. Outdoors could get also strong propagation that might be useful in malls, stadiums.

FierceWireless: Do you see LAA as an alternative to in-building systems such as distributed antenna systems?

Ray: Yes, you could place a Nokia LAA product for indoor service. We are already doing Nokia small cells so we could add LAA and consider using it outside. You won't get massive propagation and you won't put it on a tower but you could put it in a strip mall.