Enhanced heartbeat protocol for near real-time coordinated spectrum sharing with expanded use cases

Abstract

The goal of Spectrum Access Systems (SASs) and similar systems that coordinate access to shared radio frequency bands is to fairly and efficiently allocate spectrum use amongst users in a locality such as a county. In the US 3.5-GHz Citizens Broadband Radio Service (CBRS) band, a SAS communicates with secondary users (SUs) of the band through protocols as defined by the US Federal Communications Commission (FCC) and Wireless Innovation Forum (WInnForum) to allocate spectrum and update each endpoint on the status of an SU’s granted channel within the band. These protocols include heartbeats that regularly inform an SU of their permitted status and alert them to Primary User (PU) activity requiring an SU to vacate their occupied channel. The heartbeat protocol maintains continuity of communication between the SAS and the SUs to exchange minimal types of information. However, the reliance on this limited message format, combined with a synchronous protocol that enforces response times on the scale of minutes, significantly restricts the system’s capability. This limitation excludes many use cases, such as those requiring near real-time adaptation, more extensive management of transmission parameters, or the delivery of information like backup SU channel assignments.

We propose an alternative heartbeat protocol named the Enhanced Heartbeat Protocol (EHP) that uses asynchronous messaging and a strategically extended message format to enable a much wider range of use cases, including support for fast-moving swarms of unmanned aerial vehicles (UAVs) or other high-mobility applications. Simulations demonstrate that this asynchronous protocol is scalable, providing rapid and reliable notifications to a large number of SUs. Additionally, the protocol’s performance degrades gracefully as the number of SUs increases, making it more robust under various conditions compared to the current standard. The goal of our EHP is to provide SASs with more up-to-date spectrum information, enable scalable centralized systems, and introduce additional parameters to increase the utility and flexibility of SASs in diverse wireless communication scenarios.