The unwired world is getting complicated.

AT&T has fired up a new wireless data network in five cities in the last few months -- while new testimony reveals how completely LightSquared's planned high-speed network could shut down GPS signals.

On Sunday, AT&T will start marketing its new network in Atlanta, Chicago, Dallas, Houston and San Antonio. But it won't be selling a new data plan -- use of the new "4G LTE" network will be a perk thrown in with existing plans, AT&T executive Kris Rinne said.

Rinne said the network will have download speeds of 5 megabits to 12 megabits per second. That's in line with the speeds on Verizon's LTE network, which launched late last year with separate data plans.

The LTE-capable devices AT&T sells are a tablet, two USB data sticks and a mobile Wi-Fi hotspot. AT&T plans to light up the new network in ten more cities by the end of the year, but hasn't said which ones.

As that network goes up, another seems poised to go down. 

The news from AT&T came amidst fresh revelations about a new high-speed network technology from LightSquared -- and its dramatic impact on GPS signals. 

In testimony before the House Armed Services Committee on Thursday, General William Shelton, head of Air Force Space Command, detailed the results of tests from earlier this year intended to quantify the effect of LightSquared's forthcoming network on GPS. 

"Aviation receivers operating as far as 7.5 miles from LightSquared transmitters completely lost GPS and were degraded out to distances of more than 16.5 miles," Shelton said. "High precision GPS receivers such as those used for surveying and geological study requiring precise measurements were adversely affected out to 213 miles and totally lost GPS out to 4.8 miles."

Shelton noted that the State of New Mexico believes the LightSquared network could "jeopardize 911 and public safety."

He cautioned that Air Force Space Command's testing was modeled from the results of a single transmitter. However, that modeling showed that the complete network of high-powered base stations envisioned by LightSquared would degrade or completely kill GPS "at distances out to dozens of miles and even extending out to operations in space."

Shelton gave his damning testimony despite admitting that he was pressured to change his testimony in a way that would favor a large company funded by Philip Falcone, a major Democratic donor, congressional sources told Fox News.

LightSquared CEO Sanjiv Ahuja called the allegations of undue political influence "ludicrous."

"It’s difficult to charge that LightSquared has undue political influence when it was denied the opportunity to testify at today’s hearing," he said.