Impact of frequency offsets on zero crossing demodulation based receivers

In practical communication systems, frequency offsets between transmitters and receivers cannot be avoided. Both transmitter and receiver require local clocks which are usually derived from independent crystal oscillators. Typical low-cost crystals show a relative frequency tolerance of 20 ppm. Though devices with less tolerance are available, they are too expensive for most mass market devices. It is rather desirable to attempt to estimate and correct the frequency offset at the receiver side, preferably in digital domain. For regular sampling based receivers, such algorithms can be considered well-known. However, for irregular sampling schemes such as zero-crossing demodulation, neither the impact on the receiver performance nor ways of estimating and correcting frequency offsets are widely known. This manuscript is a first attempt to close this gap.