LTE Standards (802.11)

Vodafone conducts first 5 GHz aggregation trial

Debate rages on about whether LTE can live harmoniously with WiFi in the 5 GHz unlicensed band, but meanwhile supporters of the idea are pushing forward with trials to try to prove their point.

Vodafone has conducted the first live trial of LTE carrier aggregation, in which licensed and unlicensed spectrum is bonded together.

Working with Ericsson and Qualcomm, the operator said it had demonstrated that adding 5 GHz spectrum to the downlink would improve speeds for LTE users, and that there was fair coexistence with WiFi. The over-the-air test ran between Ericsson RBS 6402 small cells and a Qualcomm’s new Snapdragon X12 LTE modem, on Vodafone’s commercial network in the Netherlands. In total, 20 MHz of Vodafone’s 1.8 GHz Band 3 spectrum was aggregated with the same amount in 5 GHz.

Matthias Sauder, chief network officer at Vodafone Netherlands, said in a statement: “Our intent in deploying small cells is always to deliver the best customer experience, and we see the potential for LTE aggregation with unlicensed bands on small cells as one way to make that customer experience even better.”

Valter D’Avino, head of Ericsson’s western and central Europe region, added: “The unlicensed 5 GHz band is a shared resource and, as we have seen, it can be aggregated with LTE bands to provide a speed boost for users to improve app coverage, when spectrum is available – of course, the user also maintains their connection to Vodafone’s highly reliable LTE network, so they have a great connection no matter what.” LTE CA with 5GHz will be supported in Ericsson’s next major network software release, 16A, available by the end of this year.

In a company blog, Vodafone enlarged on the need for additional spectrum capacity, saying: “In the last three months Vodafone customers used 400 petabytes of data on their mobile phones for the first time (enough to listen to Spotify non-stop from the Stone Age to the Space Age). In our European markets, this surge in data usage is driven by customers using on average twice as much 4G data as they did on 3G. More data usage puts pressure on the licensed spectrum which Vodafone buys and so we are pleased to have become the first network in the world to successfully trial delivering LTE on a commercial network by aggregating both licensed and unlicensed bands.”

The trial used the emerging LTE-LAA (Licensed Assisted Access) technology, which will be ratified in the next LTE release. Some US carriers aim to harness 5 GHz spectrum as early as 2016 in commercial applications, because they can use an existing standard, LTE-Unlicensed. This is unsuitable for European carriers as it does not support Listen Before Talk anti-interference mechanisms, which are mandatory in Europe and many other regions in 5 GHz.

Vodafone stressed that it was “committed to developing LAA within the 3GPP standards process and has no plan to roll out the technology in Europe until that is concluded” in 2016. The operator is working on a second live trial with Huawei.

Recently, Qualcomm announced the latest set of tests which, it claims, confirm fair coexistence between LTE-Unlicensed and WiFi. However, the cable industry standards group, CableLabs, begs to differ. Whereas the LAA standards process is ongoing, and some signs of consensus are emerging between the 3GPP and WiFi communities, the LTE-U issue is far more urgent and contentious, as the technology could – FCC and other bodies willing – be deployed very soon.

Qualcomm said it followed CableLabs’ guidelines in its latest tests on its campus in San Diego, California. But CableLabs’ VP of technology, Rob Alderfer, said in an interview with IDG. “Unfortunately, our main conclusion from the three weeks we spent on site at Qualcomm is that there is no basis for definitive technical statements about LTE-U coexistence … LTE-U is in a prototype phase of development and does not possess the features that its proponents have noted are important to coexistence.”

In a company blog post, however, Dean Brenner, SVP of government affairs at Qualcomm, wrote: “The results show excellent coexistence performance for the studied test cases. The performance of WiFi in the presence of LTE-U was comparable to if not better than the examined WiFi-to-WiFi baseline scenario, demonstrating the effectiveness of LTE-U coexistence protocols.”

Earlier this month, the WiFi Alliance, which is trying to take the role of primary arbiter between the two sides and their test results, held a workshop in Silicon Valley which brought together over 100 attendees from 54 companies, including AT&T, Dell, Google, LG, Microsoft, Sony, Toyota, Verizon and ZTE. The WFA emerged more optimistic than its cable allies.

“One of the major industry concerns has been the degree of ambiguity in defining how LTE-U devices will operate, and more specifically, how this could impact fair unlicensed spectrum sharing with WiFi,” Edgar Figueroa, CEO of the WFA, said in a statement.

“A number of updates to the LTE-U specification were presented at the workshop, which we believe to be a good step toward addressing some of these concerns. We reached consensus on a number of points, including agreement that more specificity would improve the LTE-U specification and a broader set of test scenarios will be necessary to ensure fairness. There is also broad interest in collaborating on the work to establish the testing that will be required.”

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