Fast Viterbi Decoding Methods for the Co-channel Interference Canceller on Cellular DS/CDMA Systems

Daisuke TAKEDA; Yukitoshi SANADA; Masao NAKAGAWA

Fast Viterbi Decoding Methods for the Co-channel Interference Canceller on Cellular DS/CDMA Systems

Daisuke TAKEDA, Yukitoshi SANADA, Masao NAKAGAWA

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Capacity of Cellular DS/CDMA systems depends on an amount of co-channel interference (CCI). One of the effective schemes to eliminate the CCI and improve the capacity is CCI cancellers which remove the CCI by subtracting all the regenerated signals of the interfering users. These cancellers, however, suffer from the residual interference due to the symbol errors in the initial decision. Therefore, a canceller which employed error correction in the initial decision has been proposed. In this system, two Viterbi decoders per one user are needed. Therefore, the amount of calculation increases and this causes additional signal processing delay which is not preferable, especially for voice transmission. Here we propose three fast decoding methods by simplifying the second Viterbi decoder which is used for decoding after the cancellation. Method-1 uses information of the first Viterbi decoder. Method-2 utilizes information of the second correlator instead of that of the first Viterbi decoder. Method-3 is the combination of method-1 and method-2. It uses information from both the first Viterbi decoder and the second correlator. The results obtained from the computer simulation show that the ACS reduction ratio reaches up to 80% within 0.5 dB degradation in E_s/N_o.

Publication: IEICE TRANSACTIONS on Fundamentals Vol.E79-A No.12 pp.2002-2009

Publication Date: 1996/12/25

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Type of Manuscript: Special Section PAPER (Special Secton on Spread Spectrum Techniques and Applications)

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Daisuke TAKEDA, Yukitoshi SANADA, Masao NAKAGAWA, "Fast Viterbi Decoding Methods for the Co-channel Interference Canceller on Cellular DS/CDMA Systems" in IEICE TRANSACTIONS on Fundamentals, vol. E79-A, no. 12, pp. 2002-2009, December 1996, doi: .
Abstract: Capacity of Cellular DS/CDMA systems depends on an amount of co-channel interference (CCI). One of the effective schemes to eliminate the CCI and improve the capacity is CCI cancellers which remove the CCI by subtracting all the regenerated signals of the interfering users. These cancellers, however, suffer from the residual interference due to the symbol errors in the initial decision. Therefore, a canceller which employed error correction in the initial decision has been proposed. In this system, two Viterbi decoders per one user are needed. Therefore, the amount of calculation increases and this causes additional signal processing delay which is not preferable, especially for voice transmission. Here we propose three fast decoding methods by simplifying the second Viterbi decoder which is used for decoding after the cancellation. Method-1 uses information of the first Viterbi decoder. Method-2 utilizes information of the second correlator instead of that of the first Viterbi decoder. Method-3 is the combination of method-1 and method-2. It uses information from both the first Viterbi decoder and the second correlator. The results obtained from the computer simulation show that the ACS reduction ratio reaches up to 80% within 0.5 dB degradation in E_s/N_o.
URL: https://global.ieice.org/en_transactions/fundamentals/10.1587/e79-a_12_2002/_p

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@ARTICLE{e79-a_12_2002,
author={Daisuke TAKEDA, Yukitoshi SANADA, Masao NAKAGAWA, },
journal={IEICE TRANSACTIONS on Fundamentals},
title={Fast Viterbi Decoding Methods for the Co-channel Interference Canceller on Cellular DS/CDMA Systems},
year={1996},
volume={E79-A},
number={12},
pages={2002-2009},
abstract={Capacity of Cellular DS/CDMA systems depends on an amount of co-channel interference (CCI). One of the effective schemes to eliminate the CCI and improve the capacity is CCI cancellers which remove the CCI by subtracting all the regenerated signals of the interfering users. These cancellers, however, suffer from the residual interference due to the symbol errors in the initial decision. Therefore, a canceller which employed error correction in the initial decision has been proposed. In this system, two Viterbi decoders per one user are needed. Therefore, the amount of calculation increases and this causes additional signal processing delay which is not preferable, especially for voice transmission. Here we propose three fast decoding methods by simplifying the second Viterbi decoder which is used for decoding after the cancellation. Method-1 uses information of the first Viterbi decoder. Method-2 utilizes information of the second correlator instead of that of the first Viterbi decoder. Method-3 is the combination of method-1 and method-2. It uses information from both the first Viterbi decoder and the second correlator. The results obtained from the computer simulation show that the ACS reduction ratio reaches up to 80% within 0.5 dB degradation in E_s/N_o.},
keywords={},
doi={},
ISSN={},
month={December},}

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TY - JOUR
TI - Fast Viterbi Decoding Methods for the Co-channel Interference Canceller on Cellular DS/CDMA Systems
T2 - IEICE TRANSACTIONS on Fundamentals
SP - 2002
EP - 2009
AU - Daisuke TAKEDA
AU - Yukitoshi SANADA
AU - Masao NAKAGAWA
PY - 1996
DO -
JO - IEICE TRANSACTIONS on Fundamentals
SN -
VL - E79-A
IS - 12
JA - IEICE TRANSACTIONS on Fundamentals
Y1 - December 1996
AB - Capacity of Cellular DS/CDMA systems depends on an amount of co-channel interference (CCI). One of the effective schemes to eliminate the CCI and improve the capacity is CCI cancellers which remove the CCI by subtracting all the regenerated signals of the interfering users. These cancellers, however, suffer from the residual interference due to the symbol errors in the initial decision. Therefore, a canceller which employed error correction in the initial decision has been proposed. In this system, two Viterbi decoders per one user are needed. Therefore, the amount of calculation increases and this causes additional signal processing delay which is not preferable, especially for voice transmission. Here we propose three fast decoding methods by simplifying the second Viterbi decoder which is used for decoding after the cancellation. Method-1 uses information of the first Viterbi decoder. Method-2 utilizes information of the second correlator instead of that of the first Viterbi decoder. Method-3 is the combination of method-1 and method-2. It uses information from both the first Viterbi decoder and the second correlator. The results obtained from the computer simulation show that the ACS reduction ratio reaches up to 80% within 0.5 dB degradation in E_s/N_o.
ER -