Exploiting cyclostationary subscriber-loop interference by equalization

Equalization in cyclostationary interference, a situation that occurs in communication systems where neighboring channels carry digital data at similar symbol rates and in which the interference is composed of a few dominant or phase-aligned interferers, is discussed. A minimum-mean-square performance bound is derived for a continuous-time infinite-length decision-feedback equalizer in the presence of multiple cyclostationary interferers and additive white noise. This bound is evaluated in a subscriber-loop system example to show the performance improvements that can occur over the situation in which the interference is stationary, but has the same mean power spectrum as the cyclostationary interferers. These results show two important techniques which can provide opportunities for improved equalizer performance in cyclostationary interference: decreasing the misalignment of the phases of the transceiver clocks at the central office and using transmitter-pulse bandwidths which are wide relative to the symbol rate