<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 behavior of CBRS. Based on measured temporal data, a Markov model 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>
<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>
<p>In 2015, the Federal Communications Commission approved the usage of the 3.55 GHz - 3.70 GHz (i.e., band~48) spectrum opportunistically for commercial purposes. Since then, the 150 MHz bandwidth, also known as the Citizens Broadband Radio Service (CBRS), has attracted the attention of the leading telecommunication industries and the research communities. The CBRS spectrum has a hierarchical access architecture where the original owners of the CBRS spectrum, i.e., the incumbents, have the highest and uninterrupted transmission authority. As the incumbent transmission is sparse, the unused spectrum is opportunistically shared between the Primary Access License (PAL) users and the General Authorized Access (GAA) users. Both the user groups get approval to communicate on the CBRS spectrum from the Spectrum Access System (SAS), which acts as a cloud-based centralized administrator of the CBRS and is responsible for ensuring non-compromised incumbent operation on the CBRS. Note that the GAA users do not purchase the spectrum access through auction as PAL does and has the slightest preference to communicate on the CBRS. In this paper, we study the communication reliability of a GAA CBRS Device (GAA CBSD) when the approval from the SAS administrator to communicate on the CBRS spectrum is considered. Our experimental observations show that the deployed GAA CBSD remains uncommunicative for a sizable amount of the observed time duration as the SAS administrator does not allow the GAA CBSD to communicate on the CBRS to protect the incumbent/PAL transmissions.</p>
<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>
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