Frequency estimation based on constellation error in QAM modems

摘要

A method for frequency estimation in a QAM modem comprising the following steps: (1) receiving inphase and quadrature components of a QAM symbol from a carrier recovery block; (2) mapping received QAM symbol to a nearest QAM plant point using a slicer; (3) determining an instant error power of the received QAM point; (4) averaging the instant error power over a plurality of incoming QAM symbols in time domain; (5) excluding a DC component from the averaged error power; (6) translating the averaged error power without DC component from time domain into a frequency domain in order to determine the frequency spectrum of the averaged error power; (7) selecting the frequency spectrum component of the averaged error power with the maximum amplitude by using a peak detection; and (8) determining the frequency offset as the maximum frequency spectrum component of the averaged error power.