Bit-stream-arranged weighted modulation scheme for low delay spread frequency selective fading channels

Kiyoshi Kobayashi, Shuji Kubota

研究成果: Article査読


This paper proposes a bit-stream-arranged weighted modulation scheme to improve voice quality in low delay spread frequency selective fading channels. The proposed modulation scheme employs an input bit stream arrangement method that changes the bit stream order for significant bits so that they are not adjacent to each other over time; a mapping method that controls the amplitude of the modulation signals according to the importance of the bits; and modified differential encoding to prevent the error propagation from insignificant to significant bits. Computer simulations clarify that the proposed bit-stream-arranged weighted modulation scheme shows a S/N improvement of 8 dB in an 8-bit linear pulse code modulation (PCM) voice signal compared with the conventional non-weighted nf 4-shift quadrature phase shift keying (QPSK) modulation scheme. The proposed scheme also shows 3.5 dB improvement in a 4-bit adaptive differential pulse code modulation (ADPCM) voice signal. In this case, occurence of 'click noise' in recovered voice signal is halved. Although the proposed scheme increases the peak power of the modulated signals, the non-linearity of the power amplifier is not fatal.

ジャーナルIEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences
出版ステータスPublished - 1998

ASJC Scopus subject areas

  • 信号処理
  • コンピュータ グラフィックスおよびコンピュータ支援設計
  • 電子工学および電気工学
  • 応用数学


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