The nation's fourth largest carrier, Sprint, appears to be in the middle of a turnaround which carried over with the results of the latest J.D. Power Network Quality Performance survey. Out of the six different U.S. regions that the survey measured, Sprint was second or tied for second in five of them. That is a huge turnaround from three-years ago when Sprint finished dead last by a wide margin in the same survey.The survey also found that customers opting to sign up for unlimited data plans are more likely to be satisfied with their network. Sprint says that this is good news for them since it has the largest spectrum capacity of any other carrier in the states. According to Sprint, this means that it has a network built for unlimited now, and in the future.The J.D. Power survey measured the number of problems per each 100 calls. Verizon finished first, or tied for first, in all six regions which include the Northeast, Mid-Atlantic, Southeast, North Central, Southwest and the West.Led by CEO Marcelo Claure, Sprint is trying to regain some traction in the U.S. market. Earlier this month, the carrier reported its first quarterly profit in three-years source: J.D.Power , Sprint