1. A system for use in providing a wideband signal from a received narrowband signal comprising: an extracted narrowband feature vector corresponding to at least one characteristic of the narrowband signal; a narrowband codebook having one or more narrowband codebook index vectors, wherein each narrowband codebook index vector corresponds to a narrowband codebook entry; an analyzer responsive to the extracted narrowband feature vector to identify the narrowband codebook feature index vector that best matches the extracted narrowband feature vector; a signal mapper for executing a mapping function of the extracted narrowband feature vector using mapping parameters corresponding to the narrowband codebook entry associated with the narrowband codebook index vector identified by the analyzer, wherein the signal mapper generates at least one estimated wideband feature vector through execution of the mapping function; a stability analyzer for checking stability of a filter function constituted by the estimated wideband feature vector; and a generator responsive to the at least one estimated wideband feature vector to generate a corresponding wideband signal.