Clock recovery for circuit emulation services over ATM

Different Source Clock Frequency Recovery techniques for support of Circuit Emulation Services in ATM networks are presented. The architectures of the Adaptive method are analysed, in particular its application to the 2 Mbit/s CBR services emulated over ATM. One technique based on the level of the receiver buffer is modelled and designed. It depends on the fill level of the receiver buffer (FIFO), which is maintained between two limits in order to prevent buffer overflow and underflow. The system consists essentially of a PLL with an input linear dependent on the FIFO fill level and an output which is used to generate the local service clock for reading the receiver buffer. The development of the algorithm is explained and the comparison with other Source Clock Frequency Recovery methods is made.