While the Wi-Fi and LTE-U communities continue to lock horns over the timing of a Wi-Fi Alliance test regime and subsequent ability to commercially deploy LTE-U, the stakeholders in the LAA arena have managed to move forward on their coexistence specifications.
Both LTE-U and LAA envision using LTE in unlicensed spectrum, but the LTE-U version did not evolve through the traditional standards bodies like LAA has, which was one reason the Wi-Fi/cable community was miffed by its very existence.
3GPP has actively engaged with IEEE, Wi-Fi Alliance, Wi-Fi manufacturers and stakeholders to study LAA. However, that process also takes a long time, one that the LTE-U community didn't want to wait for.
Dino Flore, 3GPP TSG RAN chairman, reported that different proposals on the best coexistence mechanism have been meticulously discussed in RAN1 and captured in the technical report TR 36.889. Listen before Talk (LBT), which is a feature available in Wi-Fi that allows coexistence with other Wi-Fi nodes, was studied extensively. They evaluated multiple LBT schemes and based on the evaluation results and consensus between all involved stakeholders, "3GPP chose to specify a conservative LBT scheme that is similar to what Wi-Fi nodes use in order to ensure coexistence of LAA with Wi-Fi," he said in a blog post.
3GPP specified LAA for downlink operation in Release 13 and is currently working on specifying LAA for uplink operation in Release 14. "The constructive communication with IEEE, the Wi-Fi Alliance and other Wi-Fi stakeholders has been continued also during the Work Items," said Flore, who is senior director of technical standards at Qualcomm (NASDAQ:QCOM) and a former research engineer at ArrayComm.
Last year, before a 3GPP coexistence workshop in Beijing to discuss LAA, there appeared to be a lot of defensive posturing between the Wi-Fi/IEEE and LTE communities. However, those who attended the meeting, from both 3GPP and Wi-Fi perspectives, told FierceWirelessTech afterwards that they were pleased with the degree of collaboration that occurred. That spirit of cooperation apparently continued, as evidenced by the progress the groups are making.
Indeed, Flore said their study had participation from LTE manufacturers, Wi-Fi manufacturers, cellular operators and cable operators. Hundreds of papers and simulation results were submitted and thoroughly discussed to make sure LAA would cause no harm and share unlicensed spectrum fairly with Wi-Fi. That's one of the big concerns LTE-U opponents have cited: LTE-U's ability to fairly share unlicensed spectrum with Wi-Fi without crowding it out.
3GPP RAN4 has been working on the conformance and compliance tests for LAA and test specifications were approved for Release 13. In addition, 3GPP RAN has now tasked RAN4 to develop additional tests defining Multi-Node testing guidelines, which are due to be finalized in December 2016, according to Flore. The multi-node testing will provide additional verification of coexistence at a system level.
Analysts recently queried by FierceWirelessTech said they believe carriers like Verizon and T-Mobile, the two most vocal U.S. carrier proponents for LTE-U, are still likely to see a time-to-market advantage by using LTE-U instead of waiting for LAA because standards inevitably slip and they can probably get a head start of six or more months in terms of deployment and monetization.
- see this blog post
Verizon, T-Mobile can still get time-to-market advantage with LTE-U despite delay, analysts say
Wi-Fi Alliance: August target for coexistence test plan with LTE-U could slip into September
LAA/LTE-U makes appearance at Brooklyn 5G summit
LTE, Wi-Fi delegates collaborate, not clash, during coexistence workshop in Beijing