Signal fading due to multipath propagation severely impairs the performance of high speed mobile communication systems. The probability density function (PDF) for the envelope of the received signal using STTD (Space Time Transmitter Diversity) over correlated Nakagami fading channels with additive white Gaussian noise (AWGN) is derived in this paper. System performances of noncoherent signals over slow and flat fading channels in the presence of AWGN can be evaluated from this new PDF.

The distribution for the envelope of the received signal over frequency-nonselective slow fading channels with additive white Gaussian noise (AWGN) is derived in this paper. System performances of noncoherent M-ary signals over slow and flat fading channels in the presence of AWGN can be evaluated from the new probability density function (PDF) of the envelope.

In this paper, we analyze the error performance of coherent M-ary FSK (MFSK) signals using the union bound which is an upper bound on the bit error probability over frequency-nonselective slow Nakagami and Rician fading channels with additive white Gaussian noise (AWGN), respectively. Furthermore, the performances of uncoded coherent and noncoherent signals are compared under the fading channels. The error probability of noncoherent MFSK signals over slow and flat fading channels when AWGN is present can be derived and evaluated from the new probability density function (PDF) for the envelope of the received signals.

The performances of M-ary DPSK (MDPSK) and PSK (MPSK) systems using L-branch selection combining (SC) diversity reception in frequency-nonselective slow Nakagami fading channels are derived theoretically. For integer values of the Nakagami fading parameter m, the general formula for evaluating symbol error rate (SER) of MDPSK signals in the independent branch diversity system comprises numerical analyses with the integral-form expressions. An exact closed-form SER performance of MPSK signals under the effect of SC diversity via numerical integration is presented.