The optimal power allocation for equal-length twisted-pair channels

This paper investigates the power allocation for upstream and downstream signals in twisted-pair channels in order to maximize data rate. The channels interfere with each other in two forms: the near-end crosstalk and far-end crosstalk. These interferences can be mitigated by the joint optimization of upstream and downstream power spectral density (PSD). We derive the condition under which a subchannel is shared by both streams or monopolized by only one direction stream. In addition, the optimal power-allocation algorithm based on the greedy approach is developed under the discrete-rate constraint. Numerical results show that the optimal power-allocation achieves substantially more data rate than suboptimal schemes: the equal PSD scheme and frequency division duplexing (FDD) scheme.