Effect of Data Asymmetry on Unbalanced QPSK Signals with Noisy Phase Reference

The combined effects of data asymmetry and a noisy carrier phase reference on the bit error rate performance of an unbalanced QPSK system are examined. The results are presented in terms of the SNR loss for a nominal error rate of 10^-5, parameterized by the mean and variance of the reference phase error φ at the receiver. The effect of asymmetry on the carrier tracking loop (hence, on φ) is not included. The results show a considerable sensitivity in performance of both channels to asymmetry, the lower data rate channel being, as expected, more prone to degradation.