1. A system of estimating noise power in a scalar, multi-signal communications channel, comprising: a data sampler for collecting N data samples from communications signals received from the communications channel; a module for forming a temporal covariance matrix of the N data samples based on a model order estimate; and a noise power estimator module for computing the eigenvalue decomposition of the temporal covariance matrix and ranking resultant eigenvalues from the minimum to the maximum for determining the noise power and setting a noise threshold based on an input signal using a covariance matrix that is formed of N data samples of the signal in ut based on a model order estimate.