Telefonica and Ericsson have conducted the latest live demonstration of LTE-Unlicensed, bringing the technology closer to commercial implementation even outside the US and Korea. And with another 5 GHz LTE technology, LTE-LAA (Licensed Assisted Access) due to be standardized in 3GPP Release 13 this year, there is intense focus on these new options for mobile operators.
Some of the debates, as the platforms near reality, concern use cases and the way these systems will be sold and managed, especially in the enterprise, which will be the first major opportunity. But others revolve around the same old issues – whether LTE-U and LTE-LAA really can be a good neighbor to other 5 GHz residents, notably WiFi. This still hotly disputed, with Broadcom the latest to weigh in against unlicensed LTE, against old enemy Qualcomm. One outcome of the rows is likely to be an enhanced role for ETSI, which is working on new coexistence rules and likely to take the lead in 5 GHz LTE, rather than regulators like the FCC.
The Telefonica demo indicates that eager European operators could implement LTE-U (already standardized) rather than waiting for LTE-LAA. That has previously not been an option because Europe and many other regions, unlike the US and Korea, insist on listen before talk (LBT) anti-interference mechanisms in 5 GHz, and these are not included in the LTE-U specifications.
However, Ericsson has introduced LBT mechanisms on top of the standard LTE-U features to comply with this requirement – though regulators would still need to approve them. Telefonica’s director of radio and core networks, Angel Blazquez, insisted that there was harmony in the band, saying in a statement: “This demonstration proves that multiple technologies will coexist for best use of all spectrum and to support all deployment scenarios, widening the LTE ecosystem using the aggregation with licensed spectrum to provide the best performance experience.”
Ericsson also announced other enhancements to its LTE-U network software – as well as LBT support, it claims improved performance, and full coexistence between LTE-U and LTE-LAA on the same LAA carrier, which could encourage operators to introduce LTE-U, with the reassurance of a smooth migration to the more advanced LAA in future. That would effectively address one of the main obstacles to LTE in 5 GHz outside the US – the timing, with operators having to wait at least another year for fully standardized and tested LAA gear, at a time when they are under pressure from WiFi-oriented providers such as cablecos, armed with a WiFi platform which is itself improving all the time in terms of capacity and efficiency.
The over-the-air test used an RBS 6402 indoor picocell from Ericsson which supports 10 frequency bands and up to 300Mbps of aggregated LTE spectrum. The unlicensed band was used in conjunction with licensed frequencies. LTE-U and LTE-LAA require an anchor LTE network in a licensed band, keeping the unlicensed portion under the control of the MNO (even though the 5 GHz small cells might be owned or deployed by a third party via an MVNO deal).
A third set of technologies – LTE-LWA (LTE WiFi Aggregation) and Qualcomm’s MuLTEfire – allow LTE to run in unlicensed spectrum without a licensed-band host, and so could potentially be highly disruptive by placing LTE technologies in the hands of non-spectrum owners, as an alternative to WiFi for certain use cases.
Eric Parsons, Ericsson’s head of mobile broadband 4G/5G radio access, said the demo was a “milestone in the development of LTE-U”, adding: “With global data traffic growing exponentially, spectrum has become one of the world’s most valuable resources. By enabling the use of unlicensed 5 GHz spectrum to boost peak data rates and capacity, LTE-U helps operators extract maximum value from their spectrum investments while bringing high quality experiences to mobile broadband users everywhere.”
Like the rest of the Ericsson/Telefonica releases, there was no specific mention of WiFi at all, but while the 3GPP community may wish to forget the fact, WiFi is, of course, the incumbent technology in 5 GHz, and has a huge and powerful ecosystem to fight against any dilution of its position. Some of that fight has centered on claims of interference, while others will be centered on commercial deployment norms.
On the interference side, Broadcom weighed in again earlier this month, claiming LTE-U in its current form would be a disaster for WiFi, while LAA (or any other co-channel implementation) would significantly reduce WiFi’s range. In a presentation to the FCC, the chip company said various tests and simulations had convinced it that WiFi connections will be degraded by neighboring LTE-U or LTE-LAA. The company’s director of product marketing and government affairs, Christopher Szymanski, discussed the results of these lab tests with advisers to the FCC chairman and commissioners.