Spectrum sharing will be an increasingly important aspect of the technology and economics of LTE and 5G networks from now onwards. However, two standards approaches are developing, one on each side of the Atlantic, which may cause regional fragmentation in future.
One is ETSI’s Licensed Shared Access (LSA), which has just completed work on its initial specifications. There is a similar initiative in the US, called Authorized Shared Access (ASA), which has the same basic objectives, but is focused on that market’s specific band plans and commercial drivers. As with other connectivity standards processes where there is a cross-Atlantic divide – like V2X for connected vehicles – the two sides may converge over time, but for now, there is the danger of a split ecosystem, and uncertainty where other parts of the world will go.
The ETSI technical committed for Reconfigurable Radio Systems (TC RRS) has announced LSA specs for the 2.3 GHz to 2.4 GHz band, claiming improved support for sharing between licensed and unlicensed airwaves, and enhanced quality of service.
Its specs enable spectrum sharing coordination between LSA licensees and existing spectrum licensees whilst ensuring QoS. Extensions of the protocols to other bands may be considered in future, depending on regulatory and commercial requirements.
“ETSI’s LSA activities are a perfect example of the efficient interaction between the European Commission, CEPT and ETSI,” said Markus Mueck, chairman of ETSI TC RRS. “The regulation and standards challenges were efficiently addressed, leading to a ready-to-use package for LSA technology in Europe.”
Mueck addressed the issue of differences with the US, in an interview, saying that ETSI’s work has “substantially influenced related activities in other regions”, such as the FCC’s CBRS scheme in the 3.5 GHz band. One of the most influential examples of spectrum sharing, this sets up three levels of access to the band, and mechanisms for players with different access rights to avoid interference with one another. Federal incumbents have priority, followed by licence holders, and then there is a general access, unlicensed level.
Mueck added: “LSA-based spectrum sharing is expected to be a key element in the tool box of regulatory administrations in order to address future 5G spectrum needs.”
The first LSA tests were conducted at the start of 2016 in France. Ericsson, Qualcomm and RED Technologies used Ericsson’s access network in 2.3 GHz/2.4 GHz spectrum occupied by the French Ministry of Defence. That test focused on indoor capacity and coverage based around small cells using Ericsson’s Radio Dot together with carrier aggregation to bond the shared frequencies with existing licensed spectrum.
French start-up RED Technologies provided its dynamic spectrum assessment and management technology, which was developed for either LSA or ASA. It uses live radio environment maps and self-organizing network (SON) engines to allocate the frequencies on the most efficient basis in real time. The LTE devices were provided by Qualcomm, running on its Snapdragon processor/modems.
The indoor scenario is expected to be the primary driver for shared spectrum, as well as other methods of increasing the capacity available to mobile operators, such as running LTE in the 5 GHz band with LTE-LAA. The rise in usage of mobile data is sharpest indoors, and issues with coverage and quality are most challenging within buildings.
“Spectrum availability is a core condition for flourishing technology adoption and innovation. This LSA pilot is therefore a vital step towards the realization of Europe’s Digital Single Market,” said Wassim Chourbaji, VP of government affairs at Qualcomm, at the start of the test, while Ericsson said: “Sufficient availability of licensed spectrum will be a key asset to allow the deployment of 5G services, with the expected capacity and QoS requirements. LSA is an agile technology approach to boost capacity. The combination of licensed and unlicensed bands is a key 5G technology development area.”
The 2.3 GHz band in Europe, and 3.5 GHz in the US, have been particularly important in LSA/ASA development because both are earmarked for mobile broadband by the ITU, but remain largely in the hands of military or government users – though they have been used for WiMAX and LTE in other parts of the world. In France, for example, 2.3 GHz is used to measure missile speeds and to protect nuclear weapons, while Germany uses the spectrum to support broadcaster activities. However, these services are confined to fairly small regions, leaving most of the spectrum unused – and ripe for the LSA approach.