The office of Chicago Mayor Rahm Emanuel on Friday announced a new deal with AT&T, Verizon, T-Mobile and Sprint that will allow the city to deliver full 4G wireless service to all of its subways. The goal is to have its whole system online by the end of this year.

"By adding 4G wireless service all throughout the CTA, we are bringing 21st century technology to  every rider on every line of our 21st century transit system," said the Mayor. "This is another way that we are investing in a modern CTA to encourage ridership, make Chicago more economically competitive, and open up more economic opportunities to more residents throughout the city."

"There will be continuous 4G coverage crossing 22 miles from O'Hare airport through the underground tunnels and platforms of the Red and Blue Lines, the CTA's two busiest rail lines," the Mayor's office said, noting that the project officially started earlier this month.

Chicago isn't the only city with wireless coverage in its subways. New York City has been working to add connectivity to subway stations, though it's still considerably sparse on some lines. Chicago's effort appears more expansive.