Analysis of Controlled Packet Departure to Support Ethernet Fronthaul Synchronization via PTP

The synchronization accuracy achieved via the IEEE 1588 Precision Time Protocol (PTP) in packet-based fronthaul networks is substantially impaired by packet delay variation (PDV). Nevertheless, in the particular case of deployment over tree topologies, it is known that PDV can be avoided by controlling the departure of PTP packets such that they experience close to constant delays over the fronthaul. This paper analyzes controlled PTP departure under constraints that are peculiar to a fronthaul scenario of interest and considering that radio traffic itself behaves as background traffic relative to PTP. Since the method involves buffering of radio traffic prior to controlled PTP transmissions, its impact on buffer sizes at the baseband and radio units, and the corresponding increase in fronthaul latency are also analyzed. In the end, results collected through a self-developed FPGA-based testbed are presented.