Comparative Study of Various Frequency Equalization Techniques for Downlink of a Wireless OFDM-CDMA System(Special Issue on Multiple Access and Signal Transmission Techniques for Future Mobile Communications)
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概要
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In a wireless OFDM-CDMA system, the data-modulated symbol of each user is spread over multiple subcarriers in the frequency domain using a given spreading code. For the downlink (base-to-mobile) transmissions, a set of orthogonal spreading codes defined in the frequency domain is used so that different users data can be transmitted using the same set of subcarriers. The frequency selectivity of the radio channel produces the orthogonality destruction. There are several frequency equalization combining techniques to restore orthogonality, i.e., orthogonal restoration combining (ORC), control equalization combining (CEC) that is a variant of ORC, threshold detection combining (TDC), and minimum mean square error combining (MMSEC). The ORC can restore orthogonality among users but produces noise enhancement. However, CEC, TDC, and MMSEC can balance the orthogonality restoration and the noise enhancement. In this paper, we investigate, by means of computer simulation, how the BER performances achievable with ORC, CEC, TDC, and MMSEC are impacted by the propagation parameters (path time delay difference and fading maximum Doppler frequency), number of users, pilot power used for channel estimation, and channel estimation scheme. To acquire a good understanding of ORC, CEC, TDC, and MMSEC, how they differ with respect to the combining weights is discussed. Also, the downlink transmission performances of DS-CDMA and OFDM-CDMA are compared when the same transmission bandwidth is used. How much better performance is achieved with OFDM-CDMA than with DS-CDMA using ideal rake combining is discussed.
- 社団法人電子情報通信学会の論文
- 2003-01-01
著者
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Adachi Fumiyuki
Wireless Laboratories Ntt Mobile Communications Network Inc.: Presently Electrical And Communication
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Adachi F
Department Of Electrical And Communication Engineering Graduate School Of Engineering Tohoku Univers
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ADACHI Fumiyuki
Electrical and Communication Engineering, Graduate School of Engineering, Tohoku University
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Sao Tomoki
Electrical And Communication Engineering Graduate School Of Engineering Tohoku University
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Adachi Fumiyuki
Electrical And Communication Engineering Graduate School Of Engineering Tohoku University
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Adachi Fumiyuki
Department Of Electrical And Coimmunicalion Engineering Graduate School Of Engineering.tohoku Univer
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Adachi Fumiyuki
The Dept. Of Electrical And Communication Engineering Graduate School Of Engineering Tohoku Universi
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Adachi Fumiyuki
The Department Of Electrical And Communication Engineering Graduate School Of Engineering Tohoku Uni
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Adachi Fumiyuki
Wireless Lab. Ntt Docomo Inc.:department Of Electrical Communications At Graduate School Of Engineer
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Adachi Fumiyuki
The Department Of Electrical And Communication Engineering Graduate School Of Engineering Tohoku Uni
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Adachi Fumiyuki
The Wireless Laboratories Ntt Docomo Inc. : Presently With The Department Of Electrical Communicatio
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