An Investigation of OFDM-CDMA Waveforms Using Different Modulation Schemes on HF Multipath/Fading Channels

摘要

One of the key limitations of Orthogonal Frequency Division Multiplexing (OFDM) waveforms when used for data transmission on multipath fading channels is frequency selective fading. This type of fading can cancel out or severely degrade the signal strength of many of the OFDM tones, producing an irreducible error rate. 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 which could survive frequency selective fading and thus OFDM-CDMA was born. This paper will investigate the performance of OFDM-CDMA waveforms using different modulation schemes on HF multipath fading channels. In addition, several Multi-User Detection (MUD) schemes will be applied in the demodulation process to determine their benefits.