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

Kiyoshi Kobayashi, Shuji Kubota

Research output: Contribution to journalArticle

Abstract

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.

Original languageEnglish
Pages (from-to)1452-1458
Number of pages7
JournalIEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences
VolumeE81-A
Issue number7
Publication statusPublished - 1998
Externally publishedYes

Fingerprint

Frequency selective fading
Fading channels
Modulation
Differential pulse code modulation
Pulse code modulation
Quadrature phase shift keying
Power amplifiers
Computer simulation

Keywords

  • ADPCM
  • Frequency selective fading
  • Microcell system
  • PCM
  • Weighted modulation

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Hardware and Architecture
  • Information Systems

Cite this

@article{56360c236259498cbef77208e575d936,
title = "Bit-stream-arranged weighted modulation scheme for low delay spread frequency selective fading channels",
abstract = "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.",
keywords = "ADPCM, Frequency selective fading, Microcell system, PCM, Weighted modulation",
author = "Kiyoshi Kobayashi and Shuji Kubota",
year = "1998",
language = "English",
volume = "E81-A",
pages = "1452--1458",
journal = "IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences",
issn = "0916-8508",
publisher = "Maruzen Co., Ltd/Maruzen Kabushikikaisha",
number = "7",

}

TY - JOUR

T1 - Bit-stream-arranged weighted modulation scheme for low delay spread frequency selective fading channels

AU - Kobayashi, Kiyoshi

AU - Kubota, Shuji

PY - 1998

Y1 - 1998

N2 - 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.

AB - 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.

KW - ADPCM

KW - Frequency selective fading

KW - Microcell system

KW - PCM

KW - Weighted modulation

UR - http://www.scopus.com/inward/record.url?scp=0032116621&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0032116621&partnerID=8YFLogxK

M3 - Article

VL - E81-A

SP - 1452

EP - 1458

JO - IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences

JF - IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences

SN - 0916-8508

IS - 7

ER -