A novel approach for artificial bandwidth extension of speech signals by LPC technique over proposed GSM FR NB coder using high band feature extraction and various extension of excitation methods

This research addresses an issue of wide band (WB) speech transmission (having cut-off frequency f(c) = 8 kHz) over standard narrow band (NB) communication link (supporting bandwidth of 300-3,400 Hz). A long transition time for technological up-gradation from NB to WB systems eventually lead to development of backward compatible techniques such as artificial bandwidth extension (ABE) which is capable of providing bandwidth of 50-7,000 Hz, in turn contributing toll quality recovered speech at receiving end. This paper investigates a novel approach to compute high band (HB) features using linear predictive coding (LPC) technique at transmitter from given input WB speech corpus. These encoded features are embedded into bit stream of proposed GSM Full Rate 06.10 NB speech coder using joint source coding and data hiding technique and then transmitted to receiver. At receiver, these HB features are extracted to reproduce HB recovered speech using watermark extraction algorithm and for the same different extension of excitation techniques have been adopted and implemented. An e-test bench is created to implement this proposed ABE coder in MATLAB and series of simulations are carried out using Subjective (mean opinion score-MOS) and Objective (perceptual evaluation of speech quality-PESQ) analysis. Obtained results for both analyses advocate performance improvement of proposed ABE coder over legacy GSM 06.10 FRNB coder for various extension of excitation techniques.