Beginning in 2010, as a response to diminishing opportunities for clearing government spectrum for new commercial systems, NTIA's Institute for Telecommunication Sciences (ITS) held ISART conferences that focused on spectrum sharing. The participants and attendees at the three most recent ISART events discussed and debated the technical, regulatory, and economic factors that influence the spectrum-sharing paradigm. These symposia investigated spectrum sharing opportunities and challenges between radars and communications systems; evaluated the potential for expanded use of near real-time database systems, sensing, and other approaches to more dynamically access spectrum; and addressed the obstacles to development of a spectrum sharing infrastructure, business processes, and rules for federal and commercial sharing. (Presentations from past programs here)
In 2012, NTIA's Commerce Spectrum Management Advisory Committee (CSMAC) established a number of working groups made up of industry and government stakeholders. These working groups investigated spectrum relocation and sharing options for federal government systems in the 1695-1710 MHz and 1755-1780 MHz bands to accommodate new commercial broadband uses. While largely a success, the working group reports [WG-1] [WG-2] [WG-3] [WG-4] [WG-5] exposed a number of opportunities to enable more widespread spectrum sharing across the country. Recurring themes expressed by CSMAC members and working group participants included the need for more sophisticated and accurate interference prediction models together with simulations, measurements, and tests to better assess inter-system compatibility. These analyses exposed a number of promising system adaptations and assessment approaches that should be further evaluated, prioritized, and shepherded through standards development processes to accelerate the evolution of spectrum-sharing technologies for commercial and government systems. Verification and validation of new analytic techniques and technologies will be essential to developing stakeholder consensus and more intense use of the radio spectrum resource.
In July 2012 CSMAC created 5 Working Groups to consider ways to facilitate the implementation of commercial wireless broadband in the 1695-1710 MHz and 1755-1850 MHz bands. The Working Groups made recommendations to the CSMAC about approaches to sharing, transition and/or relocation of the government spectrum dependent systems in the band. Mark Gibson, Senior Director of business development at Comsearch and CSMAC Co-chair, will provide an overview of the methodologies and processes used throughout the CSMAC deliberations to develop the spectrum sharing analyses. Specific attention will be given to the motivations behind the various assumptions adopted by the industry and government stakeholders—highlighting their limitations and describing opportunities for further refinements. He will conclude with a discussion of research topics recommended by the working groups. Since the ISART conference is largely motivated by the CSMAC working groups’ findings, this tutorial will provide essential background for ISART conference participants who are unfamiliar with the CSMAC deliberations.
One of the recommendations of the CSMAC working groups was to consider refinement of the technical feasibility analyses. A number of the working groups used Monte Carlo techniques, but due to resource and schedule restraints, the methodologies were technically limited. For example, the simulations did not consider computation of the cumulative distribution function for aggregate interference nor did they consider the variance in pathloss provided by the propagation models that were used. Within the framework of the European Conference of Postal and Telecommunication administrations (CEPT), an advanced software tool based on the Monte-Carlo simulation methods has been developed—the Spectrum Engineering Advanced Monte Carlo Analysis Tool (SEAMCAT). Dr. Jean-Philippe Kermoal, Spectrum Engineer, European Communications Office, will provide an in depth technical overview of the methods and processes used in SEAMCAT to account for these modeling refinements. This tutorial is essential for engineers and statisticians interested in understanding the proper techniques and added complexity of incorporating higher order statistics into spectrum engineering analyses.
ISART 2015 will consider five topic areas that reflect key elements of development, deployment, and ongoing maintenance for spectrum sharing uses:
Spectrum sharing studies require the development of system simulators to assess interactions between dissimilar systems. These system simulators must incorporate a variety of models of transmitter and receiver characteristics, use case scenarios, and radiowave propagation and channel models. Commercial transmitter physical layer characteristics, which in the days of analog FM systems were simple to describe, have been supplanted by incredibly complex time and frequency duplexed systems that negotiate voice and data transmissions on the order of milliseconds. The large number of manufacturer configuration options and wireless carrier proprietary specific system configurations make it increasingly difficult to understand system characteristics. Past spectrum sharing studies, for the sake of expedience, have admitted simplified black box models. Enhancement of these studies will require increased transparency in system configurations for model development. These models, as well as emerging system simulations, must be better understood and subjected to increased scrutiny. This panel will consider some of the latest models and simulations in use today and explore approaches to standardizing reference configurations, models, and radio channel characteristics.
Modeling the radio propagation channel is the most complex element of an electromagnetic compatibility study. Propagation models are routinely employed to design for system coverage with great success. However, their application to interference scenarios involving dissimilar systems and use case scenarios is less understood. As a result, there is still considerable room to enhance the models and their applications to yield reduced uncertainties in estimates of system isolations, thereby providing additional margins to increase spectrum sharing opportunities. Furthermore, the manner in which interference effects are statistically described and aggregated requires more complex analytic techniques than have been historically applied. Also, the recent drive to better describe the effects of clutter, i.e. man-made structures and foliage, on radiowave pathloss has exposed a need to update the open models regulators use to develop rules. Where models already exist, there is increasing need to scientifically select the one best suited for a particular application. This panel will explore the multifaceted considerations required to select or develop and validate the best models for a given situation and will provide a necessary context for future spectrum sharing studies.
Past spectrum sharing studies have not only exposed the need for improved modeling and simulation but have clarified opportunities for the application of new technologies to overcome barriers. Game changing adaptations to both commercial and incumbent systems, which incorporate interference avoidance techniques customized to particular use case scenarios, are paving the way for substantial improvements in spectrum sharing. However, these technologies will add even more complexity to models and simulations, which will need to be upgraded as the technology advances. Furthermore, their imprecise development roadmaps introduce new uncertainties for program managers negotiating long term plans for system implementations and, when necessary, staged relocations of government systems into other bands. This panel will evaluate a number of new spectrum sharing radio technologies and consider approaches to gracefully implementing these disruptive technologies.
The modeling and simulation, propagation modeling, and new radio technologies panels will expose a host of complex technical considerations that must be resolved to further spectrum sharing. Every proposed model and simulation must be subjected to a rigorous and broadly approved validation testing process to promote wide scale acceptance by all involved stakeholders. Numerous test and measurement approaches have been contemplated, ranging from lab and field measurements, to test-beds, a test city, and first office applications conducted by wireless equipment manufacturers and cellular carriers. This panel will evaluate these approaches in the context of the various problem statements and study questions, with an aim to identifying promising paths forward for each circumstance.
The introduction of new technical capabilities and analysis techniques challenges regulators to adopt new processes and methods for establishing spectrum sharing rules. The increasingly sophisticated nature of new commercial technologies also raises serious concerns for system and component characterization, conformity assessment, and system wide enforcement activities. Development and adoption of these new approaches will require intensive multi-stakeholder involvement to facilitate the necessary information exchanges. Regulators may need to define the categories of information that they will need from stakeholders for risk evaluation, rulemaking, and monitoring efforts. Deliberations between regulators, industry, and existing band incumbents will be complicated by the evolving nature of the technology. Subject matter experts charged with facilitating rigorous, systematic, and, most importantly, ongoing study groups are essential to maintain the momentum that has been achieved in recent years in response to the President’s 500 MHz initiative. This panel will discuss opportunities and challenges in expanding current technical efforts with the objective of establishing standardized approaches to better position the NTIA and FCC for future spectrum sharing rulemakings.