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Abstract

This invention is related to tandem free operation (TFO) in mobile cellular systems. The present invention implements a tandem free operation by using a special feedback loop which makes the decoded parameters available, performs the comfort noise insertion and bad frame handling operations, produces the parameter quantisation indices corresponding to the output of these operations, and synchronises the speech encoders and the speech decoders in the transmission path from the uplink mobile station to the downlink mobile station. This functionality is realized by partly decoding and re-encoding the parameters and synchronising and resetting the quantiser prediction memories in a specific manner. A basic idea of the invention is, that during BFH and CNI processes, a re-encoding block produces models of encoded speech parameters from the BFH/CNI processed speech parameters. These models of encoded speech parameters are then transmitted to the receiving end. The present invention provides a solution to the problem created by predictive, more generally non-stateless encoders in TFO operation.

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First Claim