Real-Time ARQ Protocol for Improved Impulsive Noise Robustness of ADSL Systems

Impulsive noise robustness is one of the major challenges for the support of new kinds of services like video transmission via ADSL access networks. This paper investigates the application of a real-time ARQ protocol at the ADSL physical layer as an alternative to standardised forward error correction in combination with interleaving. Simulation results based on an impulsive noise model derived from field measurements show that ARQ provides significantly better error correction capabilities with the same overhead and lower end-to-end delay than FEC/interleaving. The best results can be achieved by using a second retransmission option ("second chance option") with sufficient temporal de-coupling to the original disturbance event. It is therefore strongly recommended to introduce ARQ in future standards and ADSL system implementations.