Radio channel structure for QPSK digital mobile radio

Experiments on QPSK (quadrature phase-shift keying) signal transmission and 8 kb/s TC-WVQ (transform coding with weighted vector quantization) speech coding are presented. Computer simulation of the TC-WVQ speech codec has shown that the subjective quality is comparable to that of 5-bit log PCM (pulse code modulation) at a channel bit error rate of 10/sup -2/. Computation complexity can be greatly reduced compared with that of CELP. A proposed channel structure is presented for implementation in a frequency-efficient digital mobile radio system. With QPSK and 8 kb/s TC-WVQ speech codecs, such a digital mobile radio system is as frequency-efficient existing analog systems.<
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