T-Mobile US (NYSE:TMUS) plans to enhance its LTE network coverage footprint over the next year or so using its 1900 MHz PCS spectrum, all while continuing to modernize its network with LTE Advanced components, according to a senior network executive at the carrier.

Most of T-Mobile's LTE deployment to date has been based on the company's 1700/2100 MHz AWS-1 spectrum. T-Mobile has also been buying up 700 MHz A Block spectrum to enhance its coverage footprint via the strong propagation characteristics of those airwaves. T-Mobile's 1900 MHz LTE deployment has been the less heralded aspect of its plans, but will come to the fore as the company pushes ahead with its LTE network expansion, according to Dave Mayo, T-Mobile's senior vice president of technology.

In an interview with FierceWireless, Mayo said that T-Mobile has used AWS spectrum for its urban and suburban LTE deployments, but will use 1900 MHz LTE for its rural LTE coverage, especially as the company works to bring LTE service to its entire 2G EDGE footprint by mid-2015.

Mayo noted that T-Mobile has a great deal of 1900 MHz spectrum, and that using it for LTE "radically simplifies the deployment" since T-Mobile already has GSM and HSPA+ service running on that spectrum. He said T-Mobile is using "a common antenna structure" and will be upgrading its base stations to support both GSM and LTE services. The 1900 MHz LTE deployment is "almost exclusively an equipment rip [and replace] on existing sites" and involves base stations primarily.

Mayo said T-Mobile is working with dozens of backhaul partners to ensure it has adequate backhaul to support 1900 MHz LTE service; most of the backhaul will be fiber, he said but in some cases in rural parts of the country it will be microwave.

T-Mobile says it now covers 235 million POPs with LTE and aims to cover at least 250 million by the end of 2014. The company intends to cover more than 280 million POPs with LTE by mid-2015.

Another key aspect of T-Mobile's LTE buildout is its 700 MHz deployment. T-Mobile secured A Block spectrum covering 150 million POPs from Verizon Wireless (NYSE: VZ), and in recent months T-Mobile executives have indicated the company has secured A Block spectrum covering roughly another 18 million POPs from various smaller holders of the airwaves, including CenturyLink subsidiary Actel, I-700 A Block LLC and Frontier Communications. Mayo said T-Mobile is focusing that deployment "on places where we don't have GSM coverage today."

Ericsson (NASDAQ: ERIC) said it is working with T-Mobile to expand its LTE footprint, especially using the 700 MHz spectrum. Ericsson's new deal with T-Mobile is an expansion of the 2012 contract it struck with T-Mobile to upgrade the carrier's network, and the new deployment includes RBS 6000 base station equipment, installation and integration of 700, 1900 and 1700/2100 MHz LTE Advanced radio sites and tuning services.

Nokia (NYSE:NOK) Networks is T-Mobile's other main radio access network vendor partner and is expected to make a similar announcement with T-Mobile shortly. T-Mobile has said it expects to spend between $4.3 billion and $4.6 billion on its network this year.

T-Mobile is using enhanced Single Radio Voice Call Continuity (eSRVCC) technology to ensure a seamless handover of Voice over LTE calls in LTE to existing 2G or 3G networks, and as part of that Ericsson said it has deployed its Session Border Gateway and Ericsson Media Resource System to support voice handovers. Ericsson is also using its evolved Packet Data Gateway, which interoperates with T-Mobile's existing IP Multimedia System and Evolved Packet Core network infrastructure, to enable Wi-Fi calling.

Nokia is also likely helping out with RAN-related voice handover technology. T-Mobile is working with Mavenir to enable VoLTE and is also working with Taqua on Wi-Fi calling.

Ericsson, which managed MetroPCS' network, said it is also working with T-Mobile to decommission legacy CDMA MetroPCS cell sites and to recycle the site materials.

In terms of other network technologies, Mayo noted T-Mobile has not yet said when it will be deploying carrier aggregation technology, which bonds together disparate bands of spectrum to create wider channels and produce more capacity and faster speeds. However, he said T-Mobile is "actively testing" carrier aggregation. AT&T Mobility (NYSE: T) has deployed carrier aggregation and Sprint (NYSE: S) plans to do so for its 2.5 GHz TD-LTE service by year-end.

"To the extent that we don't have contiguous spectrum, we'd sure like to be able to utilize those noncontiguous frequencies" using carrier aggregation, Mayo said.

T-Mobile has also been deploying 4x2 MIMO antenna technology in its network, especially to enhance LTE performance at the cell edge. Mayo said T-Mobile is "rolling out where we can," mainly in the middle section of the country, and that one of T-Mobile's two primary RAN vendors has the capability pre-packaged with their network gear. That is likely Nokia, since GigaOM spotted 4x2 MIMO on Nokia base stations earlier this year. Mayo said T-Mobile will bring 4x2 MIMO nationwide over time.

For more:

- see this Ericsson release

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Correction, Oct. 1, 2014: This article incorrectly stated the number of covered POPs involved in T-Mobile's 700 MHz A Block purchase from Verizon. It was for 150 million covered POPs, not 158 million.