T-Mobile has announced that it has already deployed LTE-U technology in select locations across the United States. This coincides with the launch of the Samsung Galaxy S8, the first smartphone that can take advantage of LTE-U service. T-Mobile's Chief Technology Officer, Neville Ray, has announced the availability of LTE-U service in select locations in the wireless carrier's first quarter conference, wherein he also further detailed the roadmap of LTE-U deployment in unlicensed spectrum. In this roadmap, T-Mobile will further conduct testing of its LTE-U service for the next few years, with the deployment of LAA, or Licensed Assisted Access, later on in the roadmap.
LTE-U involves the deployment of LTE service in unlicensed spectrum, especially the 5GHz frequency band populated by Wi-Fi devices. This setup aims to combine the bandwidth from the unlicensed spectrum with the frequencies already available to the wireless carriers to give cellular data a boost in responsiveness via an increased pipeline for the data. Given the possible interference of LTE-U devices on Wi-Fi networks occupying the 5GHz band, it took some time for standards to be created. One of the major compromises is the use of LAA, or Licensed Assisted Access, which uses a protocol named "Listen-Before-Talk," which allows Wi-Fi and LTE-U device coexistence by making the device look for an available radio channel to transmit on.
Neville Ray also spent some time talking about HPUE, or High-Performance User Equipment. One of T-Mobile's rivals, Sprint, has claimed that the HPUE could result in a substantial increase in the range of LTE spectrum, with the 2.5GHz LTE band experiencing an increase in the wireless coverage of around 30%, even within indoor environments. The major caveat with HPUE is that it needs TDD-LTE-capable handsets for users to take advantage of the improved range, while the majority of the US carriers are using FDD-LTE technology. Ray mentioned that he has seen discussions about how HPUE can level the playing field between high-band and mid-band frequencies, with Sprint claiming that HPUE allows 2.5GHz LTE to have the same range with 1.9GHz LTE, something Ray does not fully believe. He believes there is still some work for optimization to be done for HPUE, and even so, it might not fully result in a level playing field between the spectrum.