Cellular phone signals know no borders.

When a Mexican company began turning on its cellphone and data network along the U.S.-Mexico border, including in Juárez, in mid-August, it brought interference problems for wireless phone carriers in El Paso and other border areas. El Paso’s fire, police, and emergency medical services’ communications systems were also affected.

Altán Redes’ cellular network launch along the border also caught Federal Communications Commission officials by surprise.

FCC Commissioner Ajit Pai, in an Aug. 21 letter to Sen. Ted Cruz, R-Texas, said it was a shock “that Altán unilaterally decided to turn on its network at a time and in a manner that would directly and foreseeably cause harmful interference to U.S. cellular carriers and their customers who rely on them on a daily basis" while FCC staff and Mexico officials were still negotiating testing protocols for Altán's network.

In his letter to Pai, Cruz said, "This harmful interference issue stems from Mexico's choice to establish a spectrum band plan for its 700 MHz spectrum that is inconsistent and incompatible with those employed in the United States and Canada."

Cruz said negotiations between the two countries have yet to resolve the problem.

An Aug. 5 test of the Altán network in Juárez resulted in "a severe degradation of the communications network in El Paso," including for first responder communications systems, Cruz reported in his letter written just before Altán turned on its network in Juárez Aug. 19.

The 700 MHz band is an important spectrum available for both commercial wireless and public safety communications, according to the FCC. Several other spectrum bands also are used by wireless phone and data service providers.

El Paso Fire, Police vehicles' onboard computers have connectivity problems

Since early August, El Paso fire trucks, and city ambulances, also operated by the Fire Department, and Police patrol cars have experienced problems sending and receiving messages, and other data through onboard computers, said Enrique Duenas Aguilar, a spokesman for the El Paso Fire Department, which also oversees the police communications systems.

The Fire and Police department's two-way radios also have interference problems in some parts of town, he said.

The problems, which the Fire Department is not certain are tied to the new cellular network in Mexico, have not hurt emergency response times, Aguilar said.

"When a (computer) terminal is not working (properly), we still use (cell) phones and radios," Aguilar said. If a two-way radio is having interference, it may require a message to be repeated, he said. Fire and Police department-issued cellphones are on the T-Mobile network.

Problems also are occurring at times sending data to hospitals from heart monitors, connected to heart defibrillators on ambulances, Aguilar said. If the data can't be sent, it sometimes is called in, or is given to the hospital when the ambulance arrives there, he said.

"It does not endanger the patient," Aguilar said.

Cruz, in an Aug. 18 letter to the FCC chairman, and U.S. Secretary of State Mike Pompeo, blamed Altán's Aug. 5 test of its network in Juárez for causing problems for some El Paso fire and police emergency communications systems, and at University Medical Center, and he warned things could get worse after Altán's network is activated. He asked for prompt action from the federal agencies on Altán's interference problem along the border.

El Paso Fire Chief Mario D'Agostino said in a statement that the city's Information Technology Department, the 911 Communications District, and the Fire Department "are working together with the manufacturers of the affected equipment to resolve these issues in the quickest time possible."

The city is preparing a report on the problems to send to the FCC, he noted.

"The citizens of El Paso can be assured that the emergency response services to the community will continue as normal as these problems are addressed," D'Agostino said.

Differing reports on University Medical Center cellular problems

In his letter to federal officials, Cruz also reported that the Aug. 5 Altán test caused "a nearly complete loss of wireless network coverage for the University Medical Center" in South-Central El Paso. He noted that was only two days after the El Paso mass shooting, with 10 injured people from the shooting still being treated at UMC at that time.

However, Ryan Mielke, a UMC spokesman, said the hospital only has experienced "some spotty disruption" of cellular service at the hospital, including on Aug 5.

"Not enough to disrupt our operations, and no major problems communicating with emergency personnel," he said.

Some hospital staff have hospital-issued cellphones on the Verizon network, he said. Primarily people with Verizon and AT&T service were affected with some dropped calls, he said.

Cruz's office was told that UMC lost its wireless connection on a distributed antenna system during Altan's Aug. 5 network test, a spokeswoman for Cruz said in an email. The antenna system has since been replaced due to the problems during Altan's Aug. 5 test, the spokeswoman reported.

"The goal of the senator's outreach was to elevate the issue to protect public safety and communications on the U.S. border," the spokeswoman said. "Sen. Cruz remains committed to ensuring that the United States and Mexico will reach a mutually satisfactory solution to this issue."

Verizon has biggest problems with cross-border interference

The Mexican cellular network appears to have caused the biggest problems for Verizon Wireless, whose El Paso customers have experienced dropped calls and slow, or no data service in some areas since Altán Redes' launched its network in Juárez.

Verizon, the nation's largest wireless phone carrier, also has similar problems in the San Diego area, which also has been tied to Altán's network interference.

Officials from both Verizon and AT&T have been in contact with the FCC about the cross-border interference, spokespersons from both companies reported.

"Talks continue with the highest levels of the United States government, and our network team is making regular adjustments to the network to help mitigate the issue in the interim," Kate Jay, a Verizon spokesperson, said in an email.

"It's important to remember that people are still able to use their (mobile) devices," Jay said. "Interference really just impacts capacity, so we're most likely to hear from customers in areas where there's more network usage and/or more people."

She encouraged Verizon customers with service problems to contact the company's customer service department.

In a statement released by AT&T, the company reported that its "network team is monitoring the situation closely," but AT&T officials won't say if its customers in El Paso and other border areas are having service problems.

T-Mobile, in statement from its media relations office, said its service has not been affected by the new cellular network in Mexico.

"Sprint’s network operates in an entirely different spectrum band and is not currently experiencing any unexpected issues along the border," Roni Singleton, a Sprint spokesperson, said in an email.

FCC chairman laments '11th hour' decision by Mexico network provider

Pai, the FCC chairman, in an Aug. 21 letter to Cruz reported that FCC staff met with their Mexican counterparts in early August in Mexico City and Canada and were close to an agreement to have Altán use "certain frequencies" to test its network without causing interference to U.S. networks.

That's why Altán's "eleventh-hour" decision to activate its network along the border was a shock, Pai said.

The FCC is working with the Mexican government and other U.S. agencies to resolve the issue, Pai reported in his letter.

FCC officials had no additional comments on the issue.

Altán Redes officials say cross-border problems are governments' concern

Altán officials, in a statement, said the company is “deploying and operating its network in strict compliance with the obligations of its (Mexican) concession and the radiation protocols in force with the United States.”

However, the statement said, the issue is one to be settled by government agencies, and not by cellular network providers.

Altán Redes is an international consortium that won the right from the Mexican government to build a high-speed, 4G-LTE mobile broadband network in Mexico and sell space on it to wireless phone and Internet providers.

The network launched in March, and has been gradually expanding through Mexico.

The consortium includes several infrastructure investment funds from the United States, Canada, and Mexico, including the Morgan Stanley Infrastructure investment fund.

Vic Kolenc may be reached at 546-6421; vkolenc@elpasotimes.com; @vickolenc on Twitter.