Sprint has confirmed that Los Angeles and 20 other LTE markets are now live as it expands its big-city 4G footprint. Sprint confirmed the launches on its company blog. As well as LA, other markets include Contra Costa County, Calif., Charlotte, N.C., Norfolk, Va., and Memphis, Tenn. (See Sprint's Big City 4G LTE Gets Closer for a full list.) The third-ranked U.S. operator is trying to chase down AT&T Inc.'s and Verizon Wireless's larger 4G LTE deployments. To that end, it is presently offering people who switch their number to Sprint from another carrier a discount of up to US$100 on any smartphone with a new two-year service agreement and qualifying plan. Sprint has been asking users to hunt for the new LTE signal ahead of the launch. Early clouds of Sprint's LTE signal have been seen in NYC, according to information from mobile signal strength crowd-sourcing app MobilePulse and coverage maps at Sensorly. Sprint now has 88 LTE markets live. Here's where we're at overall with LTE in the U.S.:

— Dan Jones, Site Editor, Light Reading Mobile