T-Mobile on Tuesday became the first wireless operator in the US to add nationwide HD Voice to its network, and it has also turned on iPhone-compatible 4G service in the 1900 MHz spectrum in new areas, including Denver, Los Angeles, San Diego and Virginia Beach.

The carrier’s announcements were synced to its CES press conference.

HD Voice will only work when both parties are using T-Mobile 4G smartphones, including the HTC One S, Nokia Astound and Samsung Galaxy S III. The iPhone 5 should also be available for HD Voice service when it arrives on the carrier. T-Mobile said last month that it will begin selling Apple’s handset in 2013.  Even without official support, there are already 1.9 million iPhones on its network.

T-Mobile has invested $4 billion in this particular phase of its 4G build-out. It now claims to reach 126 million people in 46 metro areas with its latest upgrades and 229 metro areas and 220 million people with its nationwide 4G network.

Other announcements from T-Mobile on Tuesday include the option of unlimited 4G data on prepaid plans for $70 a month, a new partnership with Major League Baseball and a 4G Connect data service for notebooks and tablets. The company is also gearing up to launch its LTE network later this year, with Las Vegas slated to be the first city to get it.

It looks like T-Mobile is lined up for a massive 2013 with the iPhone, LTE and HD Voice all arriving on its network this year. That being said, it is playing a bit of catch-up to its larger competitors, so it will be interesting to see whether these additions can give it some forward momentum.

Related: iPhone 5′s HD Voice is impressive, but there’s still work to be done

Photo credit: Andrew Burton/Getty Images