1. A machine-implemented method, comprising: determining that a first user of a first mobile communication device is engaged in a call over a communications network; providing an adaptive speech recognition model comprising a speaker-dependent speech recognition model; after providing the adaptive speech recognition model, analyzing an outbound audio channel of a baseband unit of the first mobile communication device to obtain a call audio signal corresponding to audio input from one or more microphones of the first mobile communication device; and updating the adaptive speech recognition model with training data derived from the call audio signal.