Performance of non-coherent π/4-QPSK in a frequency-selective fast Rayleigh fading channel

The bit-error-rate performance of the noncoherent quaternary-phase-shift-keying modem scheme in a digital cellular mobile communication system is analyzed. The system is modeled as a frequency-selective fast Rayleigh fading channel corrupted by additive white Gaussian noise and cochannel interference. The demodulation scheme considered is differential or discriminator detection. The probability density function of the phase difference between two consecutive symbols in such a channel is derived. In the π/4-QPSK system, the information is completely contained in this phase difference. The bit error rate is then calculated by numerical integration. Numerical results show that for the recommended new USA standard system (π/4-DQPSK, f _c=850 MHz, symbol rate=24 k Baud), the bit error rate is controlled by the cochannel interference, which is expected to be between 10 and 15 dB