Title :
Does 16-QAM provide an alternative to a half-rate GSM speech codec?
Author :
Webb, W. ; Hanzo, L. ; Salami, R.A. ; Steele, R.
Author_Institution :
Dept. of Electr. & Comput. Sci., Southampton Univ., UK
Abstract :
The computational complexity, speech quality, spectral efficiency, and robustness tradeoffs of speech transmission schemes for personal communications networks (PCNs) are addressed. Differentially encoded star 16-QAM arrangements with and without oversampling and diversity are compared, in terms of robustness, to the parallel frequency-division multiplex (FDM) 16-quadrature amplitude modulation (QAM) system to find the most appropriate modem scheme. The 13.4-kb/s regular-pulse-excited-long-term predictor (RPE-LTP) speech codec is subjected to rigorous bit-sensitivity analysis in terms of both cepstral distance (CD) and segmental signal to noise ratio degradations. A twin-class embedded binary Bose-Chaudhuri-Hocqunghem bit protection scheme is devised to improve robustness. The 6.2-kBd system proposed guarantees low-complexity, high-quality speech transmissions in a bandwidth of 12 kHz for vehicular speeds of 30 mph and channel signal to noise ratios in excess of 25 dB, a value readily maintained in a microcellular PCN
Keywords :
amplitude modulation; cellular radio; codecs; computational complexity; error correction codes; frequency division multiplexing; personal communication networks; speech analysis and processing; 12 kHz; 13.4 kbit/s; 16-quadrature amplitude modulation; 30 mph; RPE-LTP speech codec; bit-sensitivity analysis; cellular radio; cepstral distance; computational complexity; differentially encoded star 16-QAM; diversity; error correction codes; half-rate GSM speech codec?; low-complexity; microcellular PCN; modem scheme; oversampling; parallel frequency division multiplex 16-QAM; personal communications networks; regular-pulse-excited-long-term predictor; segmental signal to noise ratio degradations; spectral efficiency; speech quality; speech transmission; twin-class embedded binary BCH bit protection; vehicle speed; Amplitude modulation; Cepstral analysis; Computational complexity; Frequency division multiplexing; GSM; Noise robustness; Personal communication networks; Quadrature amplitude modulation; Signal to noise ratio; Speech codecs;
Conference_Titel :
Vehicular Technology Conference, 1991. Gateway to the Future Technology in Motion., 41st IEEE
Conference_Location :
St. Louis, MO
Print_ISBN :
0-87942-582-2
DOI :
10.1109/VETEC.1991.140544