T-Mobile US (NYSE:TMUS) recently posted notably improved latency speeds on its HSPA network, according to research from OpenSignal, which has teamed up with FierceWireless to report network latency speeds of the Tier 1 U.S. wireless carriers. During the June-July timeframe, latency on T-Mobile's HSPA network dipped below 150 milliseconds, after having been above 150 milliseconds during previous testing. Sprint (NYSE: S) continued to post the highest latency speeds in LTE transmissions in the most recent test period. OpenSignal uses a panel of more than 1 million consumer devices to provide real-world data on the performance and coverage of mobile networks. For the latency test, OpenSignal runs three ICMP pings on google.com and takes the average. Click here for the full OpenSignal report.