Polarization-based zero forcing suppression with multiple degrees of freedom

Polarization-based suppression with zero forcing (ZF) is limited by similarities in the polarization-frequency response of the desired and interference signals. At subcarriers where the responses are similar, suppression of the interference also leads to suppression of the desired signal, and achievable cancellation ratios are correspondingly limited. A measure called the polarization power coupling (PPC) function is introduced for determining the impact of ZF on desired signal suppression. The PPC function provides a useful measure for predicting the magnitude of the suppression of the desired signal as a function of the subcarrier frequency. We consider the use of an additional degree of freedom (DOF), e.g., with a partially correlated or uncorrelated PPC response, to provide diversity detection for improving symbol error rate (SER) performance associated with recovery of the desired signal. The approach employs suppression diversity on a subcarrier-by-subcarrier basis and uses the PPC function to identify the ZF filter response leading to a better estimate of the desired signal symbols in each subcarrier. The method is shown to provide reduced suppression of the desired signal and to improved SER performance. An alternative use of the additional DOF is considered for suppression of a second source in a two-stage processing scheme, and a receiver architecture is proposed that exploits the diversity and suppression extensions enabled by an additional degree of freedom.