Quality of Service and Dynamic Adaptive Discrete Multi-tone Modulation

In existing DMT (discrete multi-tone) systems with adaptive bit allocation a deterioration of the transmission channel may lead to increased bit error rates, and even to the loss of connection. In most cases this disturbed channel would allow a stable transmission using a new bit allocation (possibly with reduced data rate), after a further initialization phase. We propose dynamic adaptive DMT modulation providing a new framework to avoid the costly interruption of the point to point connection by finding a smooth transition between the stable states. Different quality of service (QoS) for user and protocol data is introduced in order to support the various dynamic schemes. Backward error control is provided by an automatic repeat request (ARQ) protocol enabling quick reactions to changing channel conditions.