Decision feedback equalization with cyclostationary interference for DSL

Interference from digital signals in multipair cables has been shown to be cyclostationary. This work evaluates the performance of a decision feedback equalizer (DFE) that has forward and feedback filters in the presence of cyclostationary interference (CI) and additive white Gaussian noise (AWGN). Mathematical equations for the DFE with CI and AWGN were derived. A comparison was made between a DFE with CI and one with stationary interference (SI) to show the better of the two cases. Fractionally-spaced (FR-SP) and baud-rate DFE equalizers were compared in the presence of CI and AWGN. We have proposed the use of FR-SP DFE since it had much better performance than the baud-rate DFE. If the FR-SP DFE cannot be used because of its complexity, then we propose the use of a baud-rate DFE using the adaptive technique that searches for the receiver sampling phase which gives the best system performance in the presence of CI and AWGN. We also proposed that the transmitters' phases be the same at the central office, which results in an overall CI. This proves to be beneficial if we use a FR-SP DFE or baud-rate DFE, with an adaptive technique, for equalization at the receiver.