Synchronization of Single-Frequency Simulcast Networks Using Network Time Protocol

Single-frequency simulcast networks use two or more radio base stations (RBS) to transmit simultaneously the same signal on the same radio channel over the service area. To ensure correct operation and good performance, simulcast networks need accurate time and frequency synchronization. In this work, we designed a system for synchronizing RBS clocks by way of network time protocol (NTP) packets. The goal is to allow simulcast operation when external sources of synchronization, such as GPS, are not available or when the operator prefers to distribute timing alternatively, in particular by IP network facilities used for data transport. Time stamps are disseminated by a master RBS and used in slave stations to steer local clocks. The mechanism proposed was modelled, simulated and implemented in an experimental prototype. Simulation and experimental measurement results meet requirements and demonstrate the practical feasibility of this approach for commercial application.