A Comprehensive Analysis of Secondary Coexistence in a Real-World CBRS Deployment

The Federal Communications Commission (FCC) in the U.S. has made the Citizens Broadband Radio Service (CBRS) band (3.55 -3.7 GHz) available for commercial wireless usage under a shared approach, controlled by Spectrum Access System (SAS). This paper presents a first-of-its-kind extensive measurement campaign of a commercial CBRS network that quantifies both co-channel interference (CCI) and adjacent channel interference (ACI) caused by competing Generalized Authorized Access (GAA) devices and C-band 5G, respectively. We (i) identify a particular CCI scenario and improve performance by changing the frequency allocation based on our study of other allocations in the vicinity and (ii) quantify ACI from 5G in C-band using throughput. We investigate user-experienced propagation loss and compare it with calculated propagation loss using CBRS 1+ specified Irregular Terrain Model (ITM) and empirical signal propagation models. We conclude that (i) CCI and ACI for GAA users is not handled well by the SAS, (ii) proper frequency allocation for GAA requires additional analysis of interference from other GAA users followed by dynamical channel selection, (iii) utilization of immediate adjacent channels by high power 5G deployments limits the performance of CBRS, and (iv) CBRS 1+ specified ITM overpredicts propagation characteristics in non-line-of-sight (NLoS) area.