Receiver Windowing for FDM MFSK Signals

Abstract

Frequency division multiplexed, orthogonal <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</tex> -ary FSK modulated signals transmitted over a frequency hopping channel (with one channel use per hop) interfere with each other unless perfectly synchronized in time and frequency with the receiver. In order to maintain the interfering "crosstalk" energy at harmless levels, even in the case of grossly power unbalanced users, the frequency separation between assigned signaling frequencies must be expanded beyond the orthogonal spacing. It is found that the required bandwidth expansion can be significantly reduced by amplitude windowing at the receiver, at a cost of a slight decrease in detectability. This effect is evident through examination of both worst case, single source crosstalk and average, multiple user crosstalk.