A FREQUENCY UTILIZATION EFFICIENCY IMPROVEMENT ON SUPERPOSED SSMA-QPSK SIGNAL TRANSMISSION OVER HIGH-SPEED QPSK SIGNALS IN NONLINEAR CHANNELS

This paper proposes a superposed SSMA (Spread Spectrum Multiple Access )-QPSK (Quadrature Phase Shift Keying) signal transmission scheme over high speed QPSK signals to achieve higher frequency utilization effic iency and to facilitate lower power transmitters for SSMA-QPSK signal transmission. Experimental results show that the proposed scheme which employs the coding-rate of one-half FEC (Forward Error Correction) an d a newly proposed co-channel interference cancellation scheme for SSM A-QPSK signals can transmit twenty SSMA-QPSK channels simultaneously o ver a nonlinearly amplified high speed QPSK signal transmission channe l and achieve as ten times SSMA channels transmission as that without co-channel interference cancellation when the SSMA-QPSK signal power t o the high speed QPSK signal power ratio equals - 30 dB. Moreover, can cellation feasibility generation of the interference signals replica t hrough practical hardware implementation is clarified.