Model-Based Evaluation and Improvement of PTP Syntonisation Accuracy in Packet-Switched Backhaul Networks for Mobile Applications

Wolter, K; Reinecke, P; Mittermaier, A

doi:10.1007/978-3-642-24749-1_17

Model-Based Evaluation and Improvement of PTP Syntonisation Accuracy in Packet-Switched Backhaul Networks for Mobile Applications

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Abstract

Base stations in mobile networks have very strict frequency synchronisation (also referred to as syntonisation) requirements. As backhaul networks are migrated to asynchronous packet-switching technology, timing over packet using the IEEE 1588 Precision Time Protocol (PTP) replaces current synchronisation methods that rely on the synchronous bit clock of the network. With PTP, base-station clocks derive their frequency from the inter-packet delays of Sync messages sent by a high-quality time source at regular time intervals. Packet-delay variation (PDV) thus has a major impact on the achievable synchronisation quality, and the amount of PDV of a backhaul network determines whether the network can support frequency synchronisation of base stations. We present a simulation and an analytical approach to assessing the suitability of backhaul networks for clock synchronisation using PTP and derive two methods for reducing PDV.