A little more than half of Sprint's (NYSE: S) rural LTE roaming partners have launched LTE service, according to a Sprint spokeswoman, though it is unclear exactly which ones have done so.

Sprint spokeswoman Adrienne Norton told FierceWireless that as of today "16 carriers are operating 4G LTE service" but that because of confidentiality agreements Sprint cannot disclose which ones.

"Our partners use a variety of LTE bands, including bands 4, 5, 12 and 25," she said, in giving a status update on the program. "We're continuing to work with our device OEMs to enable additional LTE bands to expand coverage for our domestic and international roamers."

In the U.S., LTE Band 4 is the 1700 MHz AWS-1 band; Band 5 is the 850 MHz band; Band 12 is the 700 MHz A Block, which is used by T-Mobile US (NYSE:TMUS), U.S. Cellular (NYSE:USM) and several smaller carriers; and Band 25 is the 1900 MHz PCS G Block, which is one of Sprint's primary LTE bands.

Sprint is using its Rural Roaming Preferred Provider program to expand its LTE footprint, which lags those of Verizon Wireless (NYSE: VZ) and AT&T Mobility (NYSE: T). Verizon and AT&T each say they cover 308 million POPs with LTE. Sprint's LTE footprint currently covers 280 million POPs.

Sprint's rural LTE program includes reciprocal roaming agreements, letting Sprint customers roam onto the rural carriers' networks and vice versa.

In September 2014, Sprint added 15 new partners to its roaming program. With those additions the program expanded to 27 carriers, and extended coverage over 565,000 square miles in 27 states, covering a population of more than 38 million people. However, until today, Sprint had not disclosed how many carriers had actually launched service under the program. Sprint has not said how many people or how much territory is covered by live LTE networks launched via the program.

Since those 27 were announced in September 2014, Sprint has added three additional carriers, including United Wireless. The other two did not give Sprint permission to identify them, according to Norton.

For the smaller carriers, the program offers access to a larger LTE network footprint, Sprint's LTE device portfolio and in some cases the ability to lease Sprint's spectrum. Norton did not immediately respond to a request for comment on how many carriers in the program had leased spectrum from Sprint. Sprint is also working with its rural partners to get them access to network infrastructure for the 2.5 GHz band, a key element of Sprint's tri-band LTE Spark service.

Sprint has said that sometime this year it will make devices more compatible with regional carriers' networks by adding support for additional spectrum bands, including the AWS and lower 700 MHz spectrum (presumably Band 12) that are used by Competitive Carriers Association member carriers. Sprint will also support device changes that will allow regional carriers to provision, manage and brand devices independently through CCA's Device Hub.

The confirmed members of Sprint's rural LTE program include SouthernLINC Wireless; nTelos Wireless; C Spire Wireless; Nex-Tech Wireless; Flat Wireless; SI Wireless (MobileNation); Inland Cellular; Illinois Valley Cellular; Carolina West Wireless; James Valley Telecommunications; VTel Wireless; Phoenix Wireless; Bluegrass Cellular; Blue Wireless; Pine Belt Wireless; Pioneer Cellular; Public Service Wireless; Syringa Wireless; and United Wireless.

The program also includes the Rural Independent Network Alliance (RINA) members and their partners: STRATA Networks; Silver Star Wireless; All West Wireless Inc.; NNTC; Snake River Personal Communications Service; CTC Telecom Inc.; South Central Communications Inc.; Custer Telephone Wireless; and Breakaway Wireless.

Some companies, including nTelos and VTel, have been public about their support of Sprint's program and their LTE launches, but many have flown below the radar.

Verizon's similar LTE in Rural America (LRA) program, which was inaugurated five years ago, includes 21 rural and smaller carriers. Of those, 19 have launched LTE networks.

Verizon recently noted that there are 224,000 square miles covered under LRA agreements and 100,000 square miles with live LTE networks. Fully 2.9 million people are covered by the leases and there are more than 900 LTE cell sites live in LRA territory.

T-Mobile disclosed last week that it has leased its spectrum to other carriers in an effort to expand its LTE network. However, T-Mobile declined to comment on how many carriers it has leased spectrum to, what spectrum bands were leased, or how much territory those leases cover.

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