Transmission Power Ratio Optimization on Superposed Low-Speed CDMA Signal Transmission Over High-Speed OFDM Signal

In recent years, while N on- Terrestrial Network (NTN) have been attracting attention in Beyond 5G/6G, various systems via LEO (Low Earth Orbit) is superior to wide-area capability are being studied. Moreover, it is desirable to transmit high-speed signal such as video transmission systems and low-speed signal such as IoT data transmission systems simultaneously at the same transponder for effective use of LEO transponder. In this system, the use of CDAM (Code Division Multiple Access) scheme for low-speed signal enables higher frequency utilization efficiency. Therefore, low-speed signal is superposed on the same frequency band over high-speed OFDM (Orthogonal Frequency Division Multiplexing) signal has been proposed. In this paper, the BER (Bit Error Rate) performances both of high-speed OFDM signal and low-speed CDMA signal. Moreover, transmission power ratio is changed and is shown to optimize transmission power ratio.