On Temporal and Spatial Behaviors of CBRS

Abstract

<p>The recently established Citizens Broadband Radio Service (CBRS) has attracted attention because it accommodates incumbents, auctioned license holders, and unlicensed users. Incumbents retain unconstrained transmission rights, but when inactive, the unused spectrum is shared between the Primary Access License (PAL) users and the General Authorized Access (GAA) users. The spectrum sharing is controlled by a cloud-based centralized administrator, Spectrum Access System (SAS), which uses an environmental sensing capability network to establish transmission rights for PAL and GAA users without hindering the incumbents. This paper reports findings from GAA CBRS Devices' (CBSDs') deployments in California's San Diego county, which has numerous incumbents, and characterizes the temporal and spatial impact of CBRS. Based on measured data, a Markov model is developed to capture the temporal behavior of the system's state and is shown to be effective in estimating the steady state and hitting time probabilities for spectrum availability. We also recorded the availability of the CBRS spectrum, advertised by the SAS at various locations in San Diego, and found evidence of undisclosed obfuscation in the reporting of spectrum availability. We then developed two strategies that maximize the entropy of the Markov Chain's hidden states and provide more significant obfuscation than the undisclosed actions of the SAS.</p>