BANDWIDTH EFFICIENT FREQUENCY-SHIFT KEYED COMMUNICATION SYSTEMS (PCM/FM, SPECTRAL SHAPING, ERROR PROBABILITY, INTERSYMBOL INTERFERENCE, SEQUENCE ESTIMATION)

This dissertation evaluates the performance of Pulse Code Modulation with Frequency Modulation (PCM/FM). A numerical algorithm is developed to compute the power spectral density function of PCM/FM. By choosing proper baseband signaling pulse and modulation index (h), the waveform of PCM/FM can be made identical to that of MSK, SFSK, and CPFSK. Thus, the spectral property of these modulation schemes can be obtained directly from that of PCM/FM.;The lower bound on the one-shot BER performance of PCM/FM is obtained assuming a matched filter receiver. Asymptotes are then derived for the one-shot BER performance of PCM/FM with limiter/discriminator detection. Important characteristics of PCM/FM that are studied include: the phase ambiguity of the discriminator output, the adjustment of the decision statistics, and the bandwidth and time delay of the receiver front-end filter. The RPI Interactive Communications Simulator (ICS) is described and extensive simulation results of PCM/FM with limiter/discriminator detection are obtained therefrom on both the AWGN channel and the Rician fading channel. In general, the trapezoidal and the raised cosine pulses provide slightly better BER performance than the rectangular pulse for h (LESSTHEQ) 0.6, while the rectangular pulse outperforms for h (TURNEQ) 0.7.;Finally, the intersymbol interference (ISI) caused by the receiver front-end filter is examined and the sequence estimation technique is applied to mitigate the ISI effect.;The spectral efficiency of PCM/FM is evaluated based on the criteria of out-of-band power bandwidth and channel crosstalk bandwidth. The former is a useful measure of the signal spectral behavior, and the latter is a more direct measure of interference. Both spectral measures are functions of the modulation index, the baseband signaling pulse, and the shape parameter thereof. For a given bandwidth or channel separation, these two spectral measures might result in different choices of optimum baseband signaling pulses. In general, though, the rectangular pulse results in better spectral performance for very narrow bandwidths, the trapezoidal pulse outperforms for medium bandwidths, and the raised cosine pulse prevails for wider bandwidths.