Improved efficiency CDMA by constant envelope SQAM

Abstract

In order to reduce the interference into the adjacent channel and to increase the processing gain of the CDMA system, a power and spectral efficient superposed-quadrature-amplitude-modulation code-division-multiple-access (SQAM-CDMA) system is proposed. In the hard-limited power amplified channel, SQAM-CDMA has about 12-16 dB lower out-of-band power interference into the adjacent channel than that of QPSK-CDMA, and 11-15 dB lower than that of BPSK-CDMA. Assuming a 30 dB lower out-of-band interference power is required in a given RF bandwidth, the processing gain of SQAM-CDMA is increased by 7 dB over QPSK-CDMA and 9.5 dB over BPSK-CDMA in the hard-limited amplified channel.<>