Wi-Fi Alliance Issues First of Several Planned Wi-Fi/LTE-U Coexistence Test Plans

The Wi-Fi Alliance issued the first of what it says will be several plans for tests to evaluate LTE-unlicensed's impact on a Wi-Fi network. The draft LTE-U test plan follows a Wi-Fi Alliance coexistence test workshop Wednesday in California involving what the group said in a statement was "dozens of industry players" discussing test regimen and agreeing it was "sufficiently mature to begin a validation exercise." Wi-Fi interests in the cable industry have been battling with wireless carriers over whether LTE-U will interfere with Wi-Fi.

The draft test plan lays out a series of tests to be run at three signal test levels -- -50 dBm, -67 dBm and -77 dBm -- to gauge how well the equipment under test hears the Wi-Fi nodes, and the reverse. Throughput, latency and jitter also will be tested in some cases, the Wi-Fi Alliance said. The draft test plan says other factors to be tested include verifying that the equipment under test can identify and report the least-used unlicensed channel when all unlicensed channels have active Wi-Fi nodes, and verifying that the equipment under test operating in an unlicensed channel allows a new Wi-Fi network to become operational.

Both the Wi-Fi Alliance and allies said the draft test plan isn't done and can't yet be used to evaluate coexistence, because the Wi-Fi Alliance is still crafting other sets of tests. A letter to the Wi-Fi Alliance signed by such Wi-Fi backers as Cablevision, Comcast, Google and Microsoft said the draft procedures "are a recognition that consumers need more than a demonstration of LTE-U device compliance with the LTE-U Forum Coexistence Specification vendor statements, or other barometers of coexistence." The draft procedures "are generally on a good trajectory" to ensuring LTE-U devices don't disproportionately degrade Wi-Fi performance, the alliance said. The draft "does not yet represent a sufficient framework for testing coexistence," and some technical issues remain to be worked out, it said.

Wi-Fi backers said issues still to be worked out include a requirement for coexistence testing at typical Wi-Fi signal power levels rather than "unrealistically ... assuming strong Wi-Fi power levels"; testing of multichannel LTE-U operations; testing of in-device coexistence to make sure LTE-U signals don't interfere with Wi-Fi network identification and selection; and "testing of common, real-world network topologies and traffic loading scenarios rather than only testing the most simplistic cases." It's unclear whether those standards also would apply to LTE-License Assisted Access, the draft plan said.

The draft plan "is an important first step for ensuring that access to the Internet is not disrupted for millions of Wi-Fi users and other users of unlicensed spectrum," Bill Maguire, executive director of WifiForward's Save our Wi-Fi campaign, said in a statement. "Many stakeholders have raised serious and widespread concerns about the likely harm LTE-U will cause to Wi-Fi. We understand that more work needs to be done to ensure coexistence between Wi-Fi and LTE-U and we are hopeful that the WFA testing methodology still under development will address all of those concerns." LTE-U backers CTIA and Verizon didn't comment Thursday. WifiFoward members and/or sponsors include some that are part of the Wi-Fi Alliance, their websites said (see here and here), such as Broadcom, Comcast, Google and Microsoft.

Validation of the test itself is to be done with "detailed testing with real equipment," the Wi-Fi Alliance said in the draft. The alliance didn't say when it expects to have more parts of the test plans ready.