This paper deals with a variable rate discrete multi-tone modulation (DMT) system for broadband power-line communications (PLCs), based on the bit-loading algorithm proposed by Leke and Cioffi. In the proposed system a suitable LMS channel estimator is considered, which is based on the insertion of a training sequence (TS). The proposed approach will be compared with the ideal channel estimates, showing its effectiveness. Moreover, different TS lengths will be compared. The performance of the system, expressed in terms of bit-rate and bit error rate (BER), with and without an estimation error is derived by simulation under the assumption of frequency-selective multipath fading channel and additive colored Gaussian noise, according to the in-building networks model.