Its backers no longer call it LTE Unlicensed (LTE-U), though that is an apt description. Regardless, the technology now referred to as Licensed-Assisted Access (LAA) has won kudos for its performance in the 5 GHz band, with tests conducted by Huawei and NTT DoCoMo showing the approach delivers better performance in both coverage and capacity compared with current widely deployed Wi-Fi equipment based on the 802.11n standard.
The Chinese vendor and Japanese operator released results from their joint trial of LAA, which they say holds promise for offloading LTE traffic to unlicensed spectrum when data traffic on licensed spectrum becomes congested in hotspot areas. The companies noted they have been cooperating on LAA research since February 2014.
"We are very pleased to have confirmed that LAA is a viable technology for LTE and future LTE-Advanced," said Seizo Onoe, DoCoMo's executive vice president and CTO. "We aim to contribute to the standardization of this technology, which inherits the highly advanced features of LTE, to further enhance the global user experience with wireless broadband."
The companies said their LAA trial made identical bandwidth available to LTE and Wi-Fi. "The trial results indicated several times throughput improvement of LAA over WiFi for both cell-medium and cell-edge users in most of the scenarios. In addition, the cell capacity gain was approximately 1.6 times that of a single-cell scenario, with better coverage extension by LAA over Wi-Fi also observed during the test," they said.
3GPP recently renamed unlicensed LTE as LAA to stress the point to government spectrum regulators that the use of LTE on a secondary carrier in an unlicensed band would be accompanied by a licensed primary carrier, according to Said Tatesh, director, head of 3GPP standards, at Alcatel-Lucent (NYSE: ALU). "3GPP decided to emphasize that this is always assisted by a licensed band, so when regulators look at this feature they do not assume the operators need less spectrum," he told FierceWirelessTech.
Though mobile operators would prefer to gain access to additional licensed spectrum, regulators worldwide have been focusing on releasing more unlicensed spectrum, leading carriers to assess how they could better leverage spectrum as an asset. In addition to using unlicensed spectrum for data offloading from licensed bands, unlicensed spectrum might also be aggregated with licensed spectrum to increase bandwidths.
Some Wi-Fi advocates have registered displeasure at the thought that LTE might be used in unlicensed bands, but unlicensed spectrum bands have typically accommodated a number of use cases and air interfaces. Huawei and DoCoMo said they plan future tests involving techniques to ensure LAA and Wi-Fi can coexist.
- see this joint release
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