Decoder-aided multidata detection of COFDM-CDMA waveforms on HF multipath/fading channels

Orthogonal Frequency Division Multiplexing (OFDM) is a widely used technique for data transmission on multipath fading channels. The multipath component of these types of channels causes a phenomenon known as frequency selective fading. This type of fading can severely degrade or completely eliminate the signal energy of many of the OFDM tones producing an irreducible error rate, even when no noise is present. In the early 1990's, researchers combined some of the characteristics of Code Division Multiple Access (CDMA) and Spread Spectrum (SS) with OFDM in order to create a more robust modulation scheme capable of surviving frequency selective fading without the need for forward error correction (FEC) techniques and thus OFDM-CDMA was born. Similar to OFDM, FEC coding can be added to OFDM-CDMA waveforms to further improve performance (referred to as COFDM-CDMA). An additional performance improvement possible for COFDM-CDMA is to exploit the output of the FEC decoder in an iterative fashion. This paper will investigate the possible performance benefits of feeding back the decoded FEC data bits to the mutiuser (i.e. multidata) detection (MUD) scheme of COFDM-CDMA waveforms on various HF multipath/fading channels.

[1]  Anthony D. Fagan,et al.  Performance of LDPC coded spread OFDM with clipping , 2005 .

[2]  John W. Nieto.  Effects of code rate and channel estimation on OFDM and OFDM-CDMA waveforms , 2006, SPIE Defense + Commercial Sensing.

[3]  O. Edfors,et al.  An analysis of two-dimensional pilot-symbol assisted modulation for OFDM , 1997, 1997 IEEE International Conference on Personal Wireless Communications (Cat. No.97TH8338).

[4]  Jr. G. Forney,et al.  The viterbi algorithm , 1973 .

[5]  Santiago Zazo,et al.  Interactive digital voice over HF , 2003 .

[6]  C. C. Watterson,et al.  An ionospheric channel simulator , 1969 .

[7]  John W. Nieto.  Performance comparison of uncoded and coded OFDM and OFDM-CDMA waveforms on HF multipath/fading channels , 2005, SPIE Defense + Commercial Sensing.

[8]  Yasuo Hirata,et al.  High-Rate Punctured Convolutional Codes for Soft Decision Viterbi Decoding , 1984, IEEE Trans. Commun..

[9]  Henrique S. Malvar.  Modulated QMF filter banks with perfect reconstruction , 1990 .

[10]  Jean-Paul M. G. Linnartz,et al.  Multi-Carrier Cdma In Indoor Wireless Radio Networks , 1994 .

[11]  John W. Nieto.  An investigation of OFDM-CDMA waveforms using different modulation schemes on HF multipath/fading channels , 2004, SPIE Defense + Commercial Sensing.

[12]  Jeffrey G. Andrews,et al.  Performance of multicarrier CDMA with successive interference cancellation in a multipath fading channel , 2004, IEEE Transactions on Communications.

[13]  M. L. Doelz,et al.  Binary Data Transmission Techniques for Linear Systems , 1957, Proceedings of the IRE.

[14]  Stefan Kaiser.  Multi-Carrier CDMA Mobile Radio Systems-Analysis and Optimization of Detection , 1998 .

[15]  John G. Proakis,et al.  Digital Communications , 1983 .

[16]  T. J. Willink,et al.  Requirements on channel probes for automatic channel selection , 1996 .

[17]  Henrique S. Malvar,et al.  Signal processing with lapped transforms , 1992 .

[18]  J.W. Nieto,et al.  An investigation of coded OFDM and OFDM-CDMA waveforms utilizing different modulation schemes on HF multipath/fading channels , 2005, Proceedings of the 2005 European Conference on Circuit Theory and Design, 2005..

[19]  David D. Falconer,et al.  Adaptive Equalization Techniques for HF Channels , 1987, IEEE J. Sel. Areas Commun..