Abstract

The oscillators used in synchronization modules of CDMA and 3G base stations are huge in size and expensive. Applying cost effective and smaller, even more inaccurate, oscillators in timing modules are progressing research theme. The IEEE 1588v2 PTP synchronization scheme along with an adaptive control algorithm is presented to enhance the oscillators to meet the requirements of base stations during holdover mode especially situations like GPS is lost at the master and at the time of network outage. An oscillator frequency stability model is developed for the adaptive control algorithm. This model takes into account the control loop which creates the correction signal when the timing module is in locked mode. A recursive prediction error method is used to identify the system model parameters. Simulation results show that an oscillator enhanced by this scheme improves the synchronization performance significantly, compared with uncorrected oscillators. NS2 tool is used for the simulation of the PTP behavior. The results also show the benefit of explicitly modeling and analysis of the control loop. Finally the results show that with IEEE 1588 slave in operation the base station can provide an enhanced hold over duration and even if master is lost for hours.

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