Abstract：An overlapped frequency/code division multiple access (O-FCDMA) system framework was developed with the equivalent isotropic radiated power (EIRP) mask restraint to improve the spectral efficiency of multiple access systems for very small aperture terminals (VSATs) in the reverse link at the Ku band. Each user's information bits are spread by different sequences and then modulated on different subcarriers, with adjacent spectra partially overlapping. The system reduces the receiver complexity and improves the spectral efficiency. Simulations show that the reduced multiple access interference (MAI) improves the O-FCDMA system performance so that it outperforms the hybrid frequency/code division multiple access (H-FCDMA) system and approximates the optimal performance achieved by the belief propagation (BP) based joint iterative detection and decoding algorithm in direct-sequence code division multiple access (DS-CDMA) systems, with similar performance to single user systems. Moreover, the O-FCDMA system has a good compatibility with conventional DS-CDMA systems, so it can be easily implemented.
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