WiFi Alliance prepares LTE-U coexistence guidelines
When the WiFi Alliance said recently that it wanted to oversee a coexistence certification system for the emerging LTE-Unlicensed (LTE-U) technology, it provoked a storm in the cellular community in the US, where some operators hope to deploy LTE-U from next year. However, the WFA is pressing ahead to develop a set of guidelines for coexistence for the two networks, which will look to share the 5 GHz spectrum.
Having formed its Co-Existence Evaluation Program last month, it will now formulate guidelines and proposed testing mechanisms and present them to the industry on November 4, despite hostility from some players, such as Verizon and Qualcomm, which complained to the FCC that certification body for one technology should not be allowed to become the “gatekeeper” for another.
There are several LTE standards which aim to give MNOs a technology for licence-exempt bands, particularly 5 GHz, but LTE-U is the most controversial and, for those which fear its effect on WiFi, the most urgent to address. This is because it is already standardized and, subject to FCC approval and reassurances that it will not interfere with WiFi, it could be in commercial trials by the end of this year.
LTE-U can only operate in countries, such as the US, which do not mandate LBT (listen before talk) mechanisms to avoid interference in 5 GHz. MNOs in other countries will have to wait for LTE-LAA (Licensed Assisted Access), which will support LBT and will be standardized next year in 3GPP Release 13.
Hence the debates about LTE in licence-exempt frequencies are focusing heavily on LTE-U, while there are more signs of cooperation between the two sides when it comes to LAA, since there is the luxury of more time to address the various issues. Some of these are technical – will LTE damage the user experience of WiFi? Some are political – should a technology which is only realistically available to licensed spectrum owners (since a licensed LTE network acts as the anchor) be allowed into unlicensed bands? Some are practical – regardless of the principle that LE spectrum is for any technology that plays by the rules, is there room for more than one mobile broadband standard when spectrum is already becoming congested with WiFi alone?
The WFA will publish its coexistence guidelines within a few weeks and will identify some key performance indicators for neighbourliness. These guidelines will form the basis of a set of tests, which will be made publicly available and which the Alliance hopes will be the basis of a widely accepted certification program.
There is one thing both sides agree on – they would rather sort out their own differences than have the FCC do so. The US regulator has been taking a keen interest in the LTE-U debate – some argue it has gone beyond its technology neutral remit by promising to act if it is not convinced that LTE-U will be a good neighbour. Edgar Figueroa, president and CEO of the WFA, said that his organization is keen to find an industry solution, without the FCC getting involved.
The Alliance will hold a full-day workshop on the topic on November 4 in Palo Alto, Silicon Valley, where it will present its proposed guidelines and tests for comment and further input from stakeholders.
Supporters of LTE-U argue that such frameworks are unnecessary since their technology has already been shown, in tests, to cause no harmful interference and to conform to the FCC’s regulations under Part 15. Recently, three of the four national US MNOs (not Sprint) joined major vendors to form Evolve, a group which aims to promote the benefits of both LTE-U and LTE-LAA.
Figueroa said in an interview with FierceWirelessTech: “What’s unique with LTE-U is we recognize that we’re evolving into an era where the WiFi industry and WiFi Alliance are in need of collaboration and engagement with other industries, in this case LTE-U.” But that world will require broadly agreed testing regimes, and the WFA argues it has the experience to contribute = one vendor’s test results cannot be extrapolated to represent all implementations of LTE-U, added Figueroa.