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Decision Making under Uncertainty for Dynamic Spectrum Access


OBJECTIVE: Research, develop, and evaluate algorithms and technologies for Dynamic Spectrum Access (DSA) decision making under uncertainty. DESCRIPTION: Dynamic Spectrum Access (DSA) is emerging as one of the key technologies to enable the Department of Defense (DoD) to meet its increasing requirements for access to the electromagnetic spectrum [1]. DSA technologies seek to provide reliable, ad hoc access to sufficient capacity by secondary users while avoiding harmful interference to other spectrum users -- especially incumbent users. To accomplish those requirements, a DSA system must establish and maintain awareness with respect to the activity of other spectrum users as well as policies governing its access to spectrum. Awareness of in situ spectrum conditions will always contain significant degrees of uncertainty; therefore a DSA system must also make decisions under imperfect (incomplete and sometimes inaccurate) awareness. Recent and ongoing research has addressed nearly every aspect of DSA operation. Areas of significant research include spectrum sensing, multi-user access to spectrum, interference mitigation, security, regulatory frameworks, and economic considerations [2-4]. What has not been sufficiently addressed is the necessary ability to make decisions under uncertainty. Current DSA research does not include approaches for comprehensively expressing, managing, mitigating, and making decisions with imperfect awareness. Uncertainty is instead pre-factored into the formulation of regulatory rules; forcing DSA systems to sacrifice performance in the overwhelming majority of operating conditions in order to avoid rare cases (e.g., hidden nodes) leading to interference under nominal operating rules. Given a sufficient representation of knowledge uncertainty, DSA systems can make more reliable in-situ decisions under a broader range of scenarios and avoid performance loss. In this effort, the Air Force is soliciting innovative research proposals in the area of performance enhancement of DSA subject to uncertainty in current space spectrum use such as: non-existent spectrum usage data, unknown antenna side-lobe patterns, incomplete available satellite or earth station data set. Particularly, innovative algorithms and responsive technology development and demonstration for DSA decision making under uncertainty are of importance. First and foremost, uncertainty concepts must be embedded in the DSA knowledge base in a way that is scalable, enables distributed operations, and is compatible with awareness information sources. Second, an evaluation capability must synthesize DSA performance goalscapacity, interference, and costwith uncertainties in the knowledge base. Finally, awareness management mechanisms must reduce awareness uncertainties by combining information from a range of data sources including sensors, semi-static databases, and underlying network control data. PHASE I: Select a Low Earth Orbit satellite communication scenario entailing crosslink pattern design, partitions of satellite footprints, inter-satellite links with user to user delays and link margins, precedences for spectrum sharing with Geostationary Orbit satellites. Detect/track interferences using passive angle data. Identify effective approaches & algorithms for DSA subject to imperfect knowledge. PHASE II: Refine the Phase I algorithm/system concept. Demonstrate DSA benefits for inter-satellite links'channel capacities under contested environments. Assess utility of the technology against spectrum re-using/harvesting/sharing, inter-satellite link routing paths for given QoS requirements, intentional/un-intentional interference mitigation, reconfigurability of inter-satellite links to meet end-to-end traffics. Quantify spectrum availability for LEO/GEO downlinks/uplinks & user-to-user time delays. PHASE III: Dynamic DSA technologies are applicable to High Data Rate Airborne Terminal and XG DSA2100 with improvements in capacities and flexibilities. In addition, spectrum occupancy measurements are useful to multi-organizational urban surveillance networks, disaster response networks and cellular networks. REFERENCES: 1. S. Chan,"Shared spectrum access for the DoD", IEEE Communications Magazine, Vol. 45, No. 6, pp. 58-66, 2007. 2. Q. Zhao and B. Sadler,"A survey of dynamic spectrum access,"IEEE Signal Processing Magazine, Vol. 24, No. 3, pp. 7989, 2007. 3. Presidential memorandum: Unleashing the wireless broadband revolution. In Federal Register, Vol. 75, No. 126 of Presidential Documents, pp. 3838738389. US Government Printing Office, Washington, DC, 2010. 4. National Broadband Plan: Analysis and Strategy for Connecting America. NOVA Science, New York, 2011.
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