LTE's Move into the Unlicensed Spectrum Continues

Ruckus Networks July 14, 2015

A lot has been going on with the proposals for LTE Operation in Unlicensed Spectrum . The FCC recently requested industry input on LTE-U (LTE Unlicensed) and LAA (LTE Licensed-Assisted Access), 3GPP’s formal action to move both the LAA and LWA (LTE/WLAN Aggregation) programs forward, and the announcement of a standalone (fully unlicensed) version of the technology are just a couple of goings on. For some useful background, some of our previous posts detail these worlds colliding, Digging deeper into how it all works and the public love affair between LTE and WiFi. FCC Requests Public Notice for Comments On May 5^th, the FCC Office of Engineering and Technology and Wireless Telecommunications Bureau opened a Public Notice (PN 15-105) requesting input from interested parties on the topics of LTE-U and LAA technology.Initial filings were due by June 11^th, and reply comments by June 26^th. A total of 57 filings were made under this PN and the FCC definitely got a variety of wide ranging input. Ruckus provided our input in this filing. This PN was expected, as Chairman Tom Wheeler had committed to it in the remarks he made after the commission issued its recent order on the 3.5 GHz Band (the commission received so much input on LTE-U and LAA during the 3.5 GHz proceedings that they decided to have a separate PN dedicated to the topic). In the PN, the FCC made the same distinction Ruckus has been using by classifying LTE-U as a non-standard, pre-standard technology and using LAA to describe the technology development program within 3GPP. It posed 10 specific questions about these proposals, which can be summarized into the following categories:

Distinctions between LTE-U and LAA
Timelines for development and deployment
Coexistence with WiFi
Coordination of LAA development between 3GPP and IEEE 802
Support for a standalone (unlicensed only) version

Perhaps not surprisingly, the majority of the filings can be classified as representing one of 2 ‘camps (skeptics and advocates)’, which typically took different positions on the key questions (click on graphic below).

A few sample excerpts on the question of industry coordination highlight the degree of polarization: Ericsson: “There has been extensive coordination between 3GPP and IEEE 802.11 on appropriate sharing characteristics to ensure coexistence between LTE-U/LAA and 802.11/WiFi.” IEEE 802: “There has been no coordination between IEEE 802 and any standards body associated with LTE-U, because LTE-U was not developed by a standards body.” and, “There has been no coordination between 3GPP and IEEE 802 on LAA.” It will be interesting to see how the FCC reconciles these types of conflicting statements – there were many. Both Ruckus and the WiFi Alliance (WFA) took advantage of this PN to note their belief that LWA should also be under consideration as another proposal for LTE in Unlicensed Spectrum, especially as it pertains to the overall assessment of LTE and WiFi coexistence. It’s unclear at this time exactly what next steps we might see from the FCC, but they certainly have a lot of information to digest. It does seem apparent that the Commission would like to see many of these disputed points resolved through interaction between 3GPP and IEEE, and it wouldn't be surprising to see them call for tighter coordination and agreement on LAA/WiFi coexistence between those bodies. What happened in Malmö? 3GPP held a significant meeting in Malmö, Sweden last month. A number of important things occurred at that meeting:

3GPP considered all of the LAA simulation and testing results that had been generated during the Study Item (SI) period, and advanced LAA to the status of a Work Item (WI) for Release 13 (expected to be finalized in the March 2016 timeframe). The WI specifies a single global framework operating in 5 GHz, that the Rel13 version will be Supplemental DownLink (SDL) only, and that a standalone mode will not be supported. LAA Work Item

3GPP also approved LWA as a formal WI for Release 13. Unlike LAA, the LWA program was initiated as a WI, so there were no study results to consider. The WI did not specify SDL operation, so presumably LWA could support both downlink and uplink LTE data augmentation. LWA Work Item

3GPP declined a request by IEEE 802 for both organizations to jointly co-host a workshop on LAA/Wi-Fi coexistence coincident with IEEE’s meeting this month. Instead, 3GPP announced that it will host an LAA workshop in late August open to interested industry organizations. The announcement was sent to IEEE 802, WFA, WBA, GSMA, ETSI, FCC, OfCom, and CCSA. The stated goal of this workshop is “to exchange views and information on LAA”. The WFA and NCTA both noted in their reply comments to the FCC PN, that the wording of this workshop announcement, and the minutes from the Malmö discussion, indicate that the interactions at this workshop will not constitute the “coordination and agreement” that the Commission enquired about.

MuLTEfire –A Video Game or What? You’ve got to give some props to the Qualcomm marketing folks, amidst the existing alphabet soup of LTE in Unlicensed proposals – LTE-U, LAA, and LWA – it’s refreshing to have a cool term in the mix. MuLTEfire is the name given to Qualcomm’s recently announced standalone version of LTE in Unlicensed. Standalone means that, unlike LTE-U or LAA, MuLTEfire will implement the entire LTE air interface (control, downlink and uplink data, paging, etc…) in unlicensed spectrum. This will help overcome one of the principal objections to LTE-U and LAA – that they require a licensed spectrum ‘anchor’, effectively precluding anyone but an existing cellular operator from deploying these technologies. At this point there are very few technical details available about MuLTEfire, and it remains to be seen if 3GPP will consider it for future standardization. Some have questioned the timing of the MuLTEfire announcement – it was unveiled on June 11^th, the deadline for initial filings in the FCC PN, which had specifically requested information on a standalone version. Now What? The next major event that is already scheduled is the 3GPP-hosted workshop with various other industry organizations on August 29^th. It’s possible that the FCC could issue some type of statement based on the PN filings prior to the workshop, or they may decide to wait and see if the workshop provides new information to consider. And, of course, there may be other developments that aren't on the public radar at this time. So Stay tuned.

LTE's Move into the Unlicensed Spectrum Continues

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