A novel scheme for transmitting QPSK as a single-sideband signal

A novel modulation scheme for transmitting QPSK as a single sideband (SSB) signal is presented. While the theoretical spectral efficiency of the new scheme, SSB-QPSK, is identical to that of QPSK or SSB (i.e. 2 bps/Hz), it is shown that for a Rayleigh-fading mobile radio channel, SSB-QPSK is more robust to equalization imperfections than either QPSK or SSB. Additionally, it is shown that the envelope variation of SSB-QPSK is about 6 dB less than that for QPSK. For a flat Rayleigh fading channel with a one-tap equalizer, it is found that SSB-QPSK is more robust to equalizer phase errors than either QPSK or SSB. The performance in a frequency-selective Rayleigh-fading channel is evaluated with a linear equalizer, in which case it is found that if the equalizer fails to remove all the ISI, the residual ISI (and hence the BER as E_b/N₀→∞) is lower for SSB-QPSK compared to QPSK