On source timing recovery for circuit emulation in ATM networks

Circuit emulation in ATM (asynchronous transfer mode) networks is considered. In a circuit-emulation session the source node generates a periodic cell stream. As this stream passes through the ATM network, it is distorted by cell delay jitter and loss, and a corrupted aperiodic copy of the source stream arrives at the receiver (destination). Considering a special case of the problem (fixed rate and small delay jitter), a simple scheme is devised that can reconstruct the continuous bit stream from the received cell stream. Allowing for variable rate sources (e.g. fixed quality, variable rate video), the author generalizes the problem and models the received cell stream as a point process whose intensity is a bandlimited function. Based on this model, the author devises an easily implementable mechanism that reconstructs a continuous bit stream from the received cell stream at the receiver (destination). Furthermore, some strategies for improving the performance of the proposed schemes are described. These strategies include assigning a higher priority for circuit-emulation cells, providing cell header error control, and possibly using positioned cells for emulated circuits inside the network