September 20, 2016 | by Wayne Smith

The Technologies of Unlicensed Spectrum: Know the Difference

At the recent CTIA Super Mobility event, AT&T Mobility’s President and CEO Glenn Lurie delivered an eloquent presentation pointing out the direction in which the wireless industry is evolving. Between some not-so-subtle gibes at the recent net neutrality decisions and FCC’s expansion of regulation, he clearly stated the market is heading toward greatly expanding the utilization of unlicensed radio spectrum (currently occupied by Wi-Fi). He made it clear this direction is driven by the nearly 100% annual growth rate of wireless data, and that licensed spectrum is simply inadequate to accommodate this kind of growth. Following Lurie was the FCC’s Chairman, Tom Wheeler. He presented some data to defend how net neutrality has preserved the openness of the internet, and how the FCC has been opening more radio spectrum to meet today’s and tomorrow’s needs. He spoke candidly about opening the pathway for network operators to better utilize unlicensed spectrum in the current 5GHz band, but also how the FCC has adopted new rules that may open up an additional 7 GHz of unlicensed spectrum. This would nearly double the amount of unlicensed spectrum available for use. He also forecasted the unlicensed spectrum will create over $500 billion in economic value in 2017. Mr. Wheeler made it clear the unlicensed spectrum is a direct subsidy to the network operators since this spectrum is free, and that up to one-half of the network operator’s traffic will be supported by unlicensed spectrum in the near future. The important message by both speakers: Small cell radio network deployment will accelerate drastically in the near future. In what form or forms will this materialize? Multiple. These technologies will include LWA (LTE/WLAN Aggregation), LTE-LAA (license assisted access), LTE-U (unlicensed) not to mention other less known technologies. It is important to state that each of these systems partially operates in the “shared unlicensed” radio spectrum. Operating here requires LTE to share radio frequencies with Wi-Fi and to coexist in some fair manner.

Unfortunately for most consumers of today’s blogosphere output, these terms are frequently used interchangeably. Since it is critical for all stakeholders involved in these projects to have a distinct understanding of the differences of each of these technologies, we will now distinguish between the three. The 3GPP’s Releases 10, 12and 13 defined the specifications for LTE/WLAN Aggregation, also referred to as Radio Aggregation. This is where LTE operates in the network operator’s licensed spectrum and Wi-Fi operates in the unlicensed spectrum. It can be implemented in either a co-located environment where LTE and Wi-Fi are directly linked, or in an environment which is not co-located where the eNodeB manages the internetworking between the LTE and Wi-Fi radio packets. This integration increases network capacity without having to make changes to the network core. In LTE-LAA, LTE operates in both the network operator’s licensed radio frequency band and in the unlicensed 5GHz band. This technology utilizes LBT (listen before talk) technologies to minimize conflict with the local Wi-Fi signals. LTE-LAA enables the network operator to leverage the efficiencies of the LTE network core while simplifying user equipment architecture. Like LTE-LAA, the LTE of LTE-U operates in both the network operator’s licensed radio band and in the unlicensed 5 GHz band. However, this version would be implemented when LBT technologies are not required. This technology requires that “fair coexistence” between LTE and Wi-Fi radio signals exist. The specifications for this technology are currently being developed. The other overwhelming conclusion from this trend is the number of small cells will grow considerably. For companies in the wireless infrastructure construction industry, this means that small cell deployments are here; they will command smaller construction budgets than macro-cells; and the construction process must become more efficient and effective than ever before. In the next blog post, we will dive deeper into the deployment of small cells, issues to plan for when coordinating with local government teams and whether or not FCC rulings on the matter support or slow industry progression.