Noncoherent detection of FSK signals in the presence of oscillator phase noise in an AWGN channel

In an earlier study based on the European Space Agency´s Olympus satellite 30/20 GHz payload parameters, it was found that several thousands of simultaneous transmissions of 50 to 200 bits/sec each could be supported from hand-held pico-terminal Earth stations. It is well known that such low data rate signals are severely affected by the inevitable phase noise of microwave local oscillators. Noncoherent modulation schemes are generally preferred for low data rate applications because they are expected to have more robust performance in the presence of oscillator phase noise. The authors present an analysis of the performance degradation of noncoherent binary frequency shift keying (BFSK) caused by phase noise. The analysis is based on the orthogonal signal set with `mark´ and `space´ frequencies separated by the baud rate. The receiver is conventional, and consists of a pair of filters matched to the nominal `mark´ and `space´ frequencies, followed by envelope detectors and comparator. However, they introduce a Gaussian distributed frequency offset between transmitter and the receiver, leading to a mismatch between the transmitted tones and the receive filters. Results show that noncoherent BFSK is subject to an irreducible error rate in the phase noise contaminated channel