Spectrum sharing techniques for radar bands

Abstract

Facing increasing difficulties at providing additional spectrum to commercial broadband providers, regulators have begun shifting their efforts towards the study and development of innovative spectrum access models that can enable coexistence between distinct radio services in the same channels. Radar bands have been recognized as one of the most promising, appealing candidates for implementing such spectrum sharing, as they occupy a significant amount of the international spectrum, and the relocation in frequency of their incumbents would take several decades to be completed. In the US alone, more than 2.4 GHz of spectrum between the 225 and 6000 MHz is reserved for radar-reliant services. These facts have motivated several regulators’ initiatives to make some bands, namely the 3.5 GHz in the US and the 5 GHz worldwide, available for broadband radio services. On the other hand, industry bodies have identified as a major disincentive to their investment in these bands the lack of spectrum opportunities that current spectrum access methods make available for secondary use in areas where population densities is high. If a spatial separation-based sharing approach, like the Spectrum Access System (SAS) in 3.5 GHz and Dynamic Frequency Selection (DFS) in 5 GHz, is employed, the large exclusion zones required by radar systems and their heavier deployment in coastal regions and airports may block a considerable percentage of the World population living in urban areas from accessing this spectrum. In this thesis, we propose opportunistic spectrum access techniques that mitigate interference and enable the coexistence between radars and broadband small cell devices at short distances.