January 1977 | Other OT 77-109

An Approximate Method for Calculating the Performance of CPSK and NCFSK Modems in Gaussian Noise and Interference

John R. Juroshek

Abstract: The report describes a simplified method of estimating the performance of coherent phase-shift keyed (CPSK) and noncoherent frequency-shift keyed systems (NCFSK) in interference. The method used is based on the eye diagram bound and provides an upper bound estimate of the probability of a bit error given the signal-to-noise ratio and signal-to-interference ratio. Application of the bound is demonstrated both for constant amplitude,circularly symmetric (CS) interference,and amplitude-varying interference. With amplitude-varying interference,the bound requires a knowledge of the ratio of peak signal power to peak interference. The accuracy of the bound is demonstrated by comparing the bound to other predictions obtained by more exact mathematical analyses. Also described in the report is the extension of the bound to multiphase CPSK. It is anticipated that this bound will be useful primarily in studies that require a simple method of estimating degradation from interference, and where the errors due to the looseness of the bound are acceptable.

Keywords: interference; digital transmission; frequency shift keying (FSK); demodulator; multiphase shift keying; probability of error

Disclaimer: Certain commercial equipment, components, and software may be identified in this report to specify adequately the technical aspects of the reported results. In no case does such identification imply recommendation or endorsement by the National Telecommunications and Information Administration, nor does it imply that the equipment or software identified is necessarily the best available for the particular application or uses.

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