Methods and apparatus for retiming and realigning sonet signals

Abstract

Methods for retiming and realigning SONET signals include demultiplexing STS-1 signals from an STS-3 signal, buffering each of the three signals in a FIFO, determining the FIFO depth over time, determining a pointer leak rate based in part on FIFO depth and also based on the rate of received pointer movements. For a 28-byte deep FIFO, if the depth of a FIFO is 12-16 bytes, no pointer leaking is performed. If the depth is 0-4 bytes, an immediate positive leak is performed. If the depth is 24-28, an immediate negative leak is performed. If the depth is 5-11 bytes a calculated positive leak is performed. If the depth is 17-23 bytes, a calculated negative leak is performed. The calculated leak rates are based on the net number of pointer movements (magnitude of positive and negative movements summed) received every 32 seconds (256,000 frames).

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