In an embodiment, a central coordination server (e.g., a Spectrum Access Server) partitions a shared communication medium into a contention-free partition where the shared communication medium is reserved for devices associated with a first set of operators and a contention-based partition where devices associated with a second set of operators contend for access to the shared communication medium, at least one operator belonging to both the first and second sets of operators. The central coordination server notifies target devices (e.g., APs, ATs, etc.) of the partitioning. In a further embodiment, a device (e.g., AP, AT, etc.) communicates over a portion of the contention-free partition that is reserved for an associated operator, and also over the contention-based partition.