Synchronization Algorithms for TDD Fronthaul in PTP-Unaware Networks

Abstract

In fifth-generation (5G) mobile communications, clock synchronization is essential for the correct operation of the network. In this context, as 5G networks are moving to packetbased networks, the IEEE 1588 precision time protocol (PTP) is the industry-accepted protocol for flexibly distributing time synchronization. However, when PTP packets are transported in a cost-effective network without specialized equipment, two main issues impact the performance of PTP: packet delay variation (PDV) and delay asymmetries. In this type of network, the use of algorithms to filter the errors introduced by PDV and delay asymmetry is usually helpful. Thus, this work aims to present an analysis of PTP performance on a cost-effective network when time-division duplex (TDD) is used on the radio interface. We propose new algorithms to improve the PTP performance that take advantage of the fronthaul (FH) periodic utilization pattern when using TDD on the radio interface. Our evaluation is carried out on a realistic testbed composed of field-programmable gate arrays (FPGAs). The results indicate that the PTP performance can be improved on this type of network by using the knowledge about the FH periodicity to correct the queuing-induced asymmetry and more effectively filter the PDV.