| Summary: | 碩士 === 國立成功大學 === 電機工程研究所 === 83 === Most of the researches on speech signal coding have put
emphasis on the speech quality and the character of source
coding , but seldom taked into consideration the effect of
channel noise to speech signal transmission. Due to this reason
, we combined source coding and channel coded modulation to
obtain the better transmission performance without expanding
bandwidth. We have studied several broadly accepted speech
standards-- ADPCM, CELP,and American IS-96 (speech coding
standard for IS -95), and learned the source coding principles
and procedures. We have also studied the schemes to estimate
the speech quality and selected for the proper methods that can
be used in our works. We then used the simulations to find the
impacts of individual source coding bit on the speech quality
by controlling error bits and divide the coding bits into
several groups according to their significance on the quality.
The UEP coded modulation scheme is then adopted to give unequal
protection capability for different bit groups. Combining such
source coding and UEP coded modulation, we can achieve an
improvement of communication quality.
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