Woodard, J. and Hanzo, L.
A Re-Configurable Speech Transceiver.
In, Proc. of 2nd International Workshop on Mobile Multimedia Communications, Bristol University, UK,
11 - 14 Apr 1995.
A dual-rate 4.7/6.5 kbits/s algebraic code excited linear predictive (ACELP) codec is proposed for adaptive speech communicators, which can drop their source rate and speech quality under network control in order to invoke a more error resilient modem amongst less favourable channel conditions. Sourcematched Bose-Chaudhuri-Hocquenghem (BCH) codecs combined with un-equal ,protection diversityand pilot-assisted 16- and 64level quadrature amplitude modulation (16-QAM, 64-QAM) are employed in order to accommodate both the 4.7 and the 6.5 kbits/s coded speech bits at a signaling rate of 3.1 kBd. In a bandwidth of 200 kHz 32 time slots can be created, which allows us to support i n excess of 50 users, when employing packet reservation multipleaccess (PRMA). Good communications quality speech is delivered in an equivalent bandwidth of 4 kHz, if the channel signal-to-noise ratio (SNR) and signal-to-interference ratio (SIR) are in excess of about 15 and 25 dB for the lower and higher speech quality 16-QAM and 64-QAM systems, respectively.
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