Performance comparison of multi-user detectors for the downlink of a broadband MC-CDMA system

Source: DBLP


In this paper multi-user detection techniques, such as Parallel and Serial Interference Cancellations (PIC & SIC), General Minimum Mean Square Error (GMMSE) and polynomial MMSE, for the downlink of a broadband Multi-Carrier Code Division Multiple Access (MCCDMA) system are investigated. The Bit Error Rate (BER) and Frame Error Rate (FER) results are evaluated, and compared with single-user detection (MMSEC, EGC) approaches, as well. The performance evaluation takes into account the system load, channel coding and modulation schemes.

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Available from: Maryline Helard, Jun 22, 2013
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    • "If the number of and the spacing between subcarriers is appropriately chosen, it is unlikely that all of the subcarriers will be located in a deep fade and consequently frequency diversity is achieved. When the orthogonality of codes is disturbed while transmission, it results in MAI which will reduce the performance of the system [7] [8]. So to enhance the overall performance of the system the data is encoded using LDPC encoder at the transmitter and at the receiver it is decoded iteratively using a turbo decoder [9]. "
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    ABSTRACT: Multi carrier code division multiple access (MC-CDMA) is an efficient multi carrier modulation (MCM) technique that mitigates problems like spectral limitation and distortion due to multipath channels. Nevertheless, in a high speed mobile communication channels the orthogonality among subcarriers are destroyed due to multipath fading. The loss of orthogonality can cause inter carrier interference (ICI) and multiple access interference (MAI). The effect of MAI reduces the system performance in term of bit error rate (BER). The Turbo block code (TBC) technique based low density parity check (LDPC) code is proposed to overcome the MAI. It provides better concatenated decoding scheme with lower complexity and higher efficiency for improving the performance of MC-CDMA system in terms of BER and the same is proved through simulation.
    2015 2nd International Conference on Electronics and Communication Systems (ICECS), Coimbatore; 02/2015
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    • "Super orthogonal turbo codes (SOTC) are low-rate convolutional codes [6] [7] chosen since it outperforms other existing codes and reduces complex detection to a great extent. However, the complexity of decoding increases exponentially as the number of users increases [8] and to reduce this problem, MUD techniques such as parallel and serial interference cancellation (PIC & SIC), general minimum mean square error (GMMSE) and polynomial MMSE has been proposed. Signal detection schemes [9] such as minimum mean square error (MMSE), zero forcing (ZF), sphere decoding (SD), Q-less QR decomposition are studied for different modulations to analyze system performance. "

    International Journal of Computer Applications 07/2013; 73(13):12-19. DOI:10.5120/12800-9885
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    • "To reduce complex detection, various MUD techniques [10] such as; parallel interference cancellation (PIC), serial interference cancellation (SIC), general minimum mean square error (GMMSE) in MC- CDMA system was considered. Further, efficient decoding algorithms such as Maximum a posteriori (MAP) algorithm [15], log MAP algorithm and soft out viterbi algorithm (SOVA) were premeditated to proffer enhanced performance [11] [12]. Hence to enhance the performance and offer high data rate, MC-CDMA system based SDR using super orthogonal turbo code is proposed in this work. "
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    ABSTRACT: Multi Carrier-CDMA, a combination of CDMA and OFDM has become a promising access technique for next generation wireless communication. It offers high speed data rate, flexible bandwidth allocation and enhanced performance to each user simultaneously. To further realize the benefits of MC-CDMA, it is made adaptable in the physical layer of software defined radio (SDR) where SDR is defined as a reconfigurable hardware with inbuilt software modules. Thus a MC-CDMA system based SDR is constructed which can be best suited for developing standards. However, as the number of users increases, due to overlapping of signals, orthogonality of the OFDM part is not maintained. It results in multiple access interference (MAI) which degrades the system performance in the downlink. To mitigate these effects, multi user detection techniques (MUD) is used. In this paper, MC-CDMA based SDR using super orthogonal turbo code (SOTC) is proposed and compared with MC-CDMA using Walsh Hadamard (WH) codes. The bit error rate (BER) is evaluated using the two codes and performance analysis is observed.
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