Maximum likelihood decoding of M-ary orthogonal modulated signals for multi-carrier spread-spectrum systems

Dekorsy, A.; Fischer, Sven; Kammeyer, Karl‐Dirk

doi:10.1109/pimrc.1998.734261

Cited by 9 publications

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References 9 publications

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“…Therefore, we will confine our discussion to QPSK ( , ) throughout the paper. For QPSK, (4) reduces to else (6) and the squared Euclidean distance between two code symbols can be expressed by (7) Equation (6) shows that there exists only one code word with a code word distance of . This complex-valued code word comprises the same WH word , but its QPSK symbol is antipodal to that of the reference (zero) word.…”

Section: Fig 2 Illustrates the Construction Of Cwcs A Block Ofmentioning

confidence: 99%

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Low-rate channel coding with complex-valued block codes

Dekorsy¹,

Kuehn

Kammeyer

2003

IEEE Trans. Commun.

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This paper addresses aspects of channel coding in orthogonal frequency-division multiplexing-code-division multiple access (OFDM-CDMA) uplink systems where each user occupies a bandwidth much larger than the information bit rate. This inherent bandwidth expansion allows the application of powerful low-rate codes under the constraint of low decoding costs. Three different coding strategies are considered: the combination of convolutional and repetition codes, the code-spread system consisting of one single very low-rate convolutional code and a serial concatenation of convolutional, Walsh-Hadamard and repetition code. The latter scheme is improved by combining the Walsh-Hadamard codes with an additional -phase-shift keying modulation resulting in complex-valued Walsh-Hadamard codes (CWCs). Analytical performance evaluations will be given for these codes for the first time. The application of CWCs as inner codes in a serial code concatenation is also addressed in this paper. We derive a symbol-by-symbol maximum a posteriori decoding algorithm in the complex signal space in order to enable iterative decoding for the entire code. A comprehensive performance analysis by simulation of all the proposed coding schemes shows that the Walsh-Hadamard-based schemes are the best choice for low-to-medium system load. Note that even for fully loaded OFDM-CDMA systems, the concatenation with an inner complex-valued Walsh-Hadamard code leads to a bit-error rate less than 10 5 for an 0 of about 6 dB. Index Terms-Block codes, code-division multiple access (CDMA), concatenated coding, iterative decoding, orthogonal frequency-division multiplexing (OFDM), turbo codes. where he conducts research projects on UMTS. His current research interests are mainly smart antenna solutions and interference cancellation techniques, as well as radio resource management algorithms for third-generation mobile standards.Volker Kuehn (M'00) was born in Paderborn, Germany, in 1966. He received the M.Sc. degree in electrical and electronics engineering from the University of Paderborn, Paderborn, Germany, in 1993, and the Ph.D. degree in communications engineering in 1998 from the same university.Currently, he is with the Department of Communications Engineering at the University of Bremen, Bremen, Germany. His main fields of interest are error-correcting codes and iterative decoding, as well as CDMA.Karl-Dirk Kammeyer (M'95) received the M.Sc. degree in electrical engineering In 1995, he was appointed Professor for Telecommunications at the University of Bremen, Bremen, Germany. His research interests are digital (adaptive) systems and signal processing in mobile communication systems (GSM, UMTS, multicarrier systems). Since 1989, he has been active in the field of higher order statistics. He holds 14 patent families, and has published two course books as well as 75 technical papers.

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Section: Fig 2 Illustrates the Construction Of Cwcs A Block Ofmentioning

confidence: 99%

“…First, we define as the effective length of error events, i.e., the code word differs in positions from the reference word . Note that for CWCs, the code symbol distances in (7) are identical at these positions. Hence, we can omit the subindex .…”

Section: Performance Analysismentioning

confidence: 99%

Low-rate channel coding with complex-valued block codes

Dekorsy¹,

Kuehn

Kammeyer

2003

IEEE Trans. Commun.

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A new OFDM‐CDMA Uplink Concept with M‐ary Orthogonal Modulation

Dekorsy

Kammeyer

1999

Trans Emerging Tel Tech

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This paper proposes the application of M-ary orthogonal Walsh modulation for an OFDM-CDMA uplink transmission. Beside the examination of general system properties, it is shown that decision-directed phase estimation represents a channel estimation concept suitable for the new system. The Walsh modulation can also be interpreted as a linear block code with low decoding complexity, and the paper concerns the serial concatenation of convolutional codes (CC) with Walsh modulation. New aspects arise since the CC mainly operates in time domain, and the Walsh modulation is merely arranged in frequency domain. In this context, we derive the bit specific reliability information for maximum likelihood (ML) soft decoding of the CC and discuss the trade-off between coding and spreading in case of sufficient and non-sufficient frequency interleaving. Throughout the discussions, the results are always compared with BPSK modulation performance, and it can clearly be demonstrated that kf-ary Walsh modulation significantly outperforms BPSK modulation in all aspects considered in this work.Although the specific simulations are related to the European Hiperlan/2 standardization, the results are valid in general.

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The Performance of Multicarrier CDMA for the Correlated Rayleigh Fading Channel

Schulze

2001

AEU - International Journal of Electronics and Communications

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Maximum likelihood decoding of M-ary orthogonal modulated signals for multi-carrier spread-spectrum systems

Cited by 9 publications

References 9 publications

Low-rate channel coding with complex-valued block codes

Low-rate channel coding with complex-valued block codes

A new OFDM‐CDMA Uplink Concept with M‐ary Orthogonal Modulation

The Performance of Multicarrier CDMA for the Correlated Rayleigh Fading Channel

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