Unlicensed LTE spectrum, known as LTE-U, is a technology that allows carriers to extend their mobile network coverage by using spectrum in frequencies for which there is no operating license. This currently and typically means using the 5 GHz frequency point, which is currently relatively quiet but shared with some 802.11 WiFi hotspots. Because this frequency point is unlicensed, it is available to any and everybody wishing to broadcast and the reason why WiFi routers (and associated radios in devices) operate at this frequency is because it is relatively uncluttered. As it happens, the 5 GHz frequency is particularly suited to high speed unlicensed networking because the higher the frequency, the greater the potential transfer speed but also the shorter the range of the transmitter. Carriers should not simply rely on unlicensed spectrum but instead will be pairing up unlicensed spectrum with their existing network to provide aggregated coverage.
In the mobile device industry, there is massive potential for unlicensed 5 GHz LTE coverage to provide additional capacity in places of high congestion. As you might understand, companies interested in WiFi technologies have raised concerns about carriers using this spectrum to crowd out wireless access points and there has been much work on keeping things fair. This is good for the industry because if left unchecked, it's possible that the highest powered transmitter will effectively block out other transmitters in a localized area and this is detrimental for most customers! There are a number of technologies currently being deployed or tested including an adaptive duty-cycle (to promote coexistence within the same spectrum) and Listen Before Talk techniques, which are being considered for a revised LTE standard.
Qualcomm have today announced that they are integrating LTE-U into their mobile chipsets following successful trials. These trials included testing the technology in an environment saturated with LTE-U and WiFi access points at the 5 GHz frequency. Qualcomm's data "concluded that LTE-U can not only provide superior performance than either LTE or Wi-Fi used individually, but fairly coexists with Wi-Fi. In many cases, shifting traffic from Wi-Fi to LTE-U can actually improve performance for Wi-Fi users…" The LTE-U technology will be integrated into the FSM99xx models, available from the second half of the year. FSM99xx will include 3G, 4G LTE, up to 802.11ac WiFi and of course LTE-U. Qualcomm has also announced the first commercially available LTE-U modem unit, the FTR8950; this will be available for commercial sampling in the second half of the year.
These chipsets will be demonstrated at next week's Mobile World Congress in Barcelona, Spain and we'll be there to take a look!