Spectrally Efficient DMT Operation with BER-Informed Dynamic Bit and Power Loading

Abstract

This paper elucidates the relative benefits of bit loading and power loading for discrete multitone (DMT) modulation over wireline links. There is considerable variability in the use of bit and power loading in recent research on DMT for wireline applications. Here, we first compare different combinations of bit and power loading schemes in simulations. We propose a method for dynamically adjusting DMT bit and power profiles based on the bit error distribution across sub-channels, as determined by the receiver. We then present experimental results showing DMT operation at 75 Gb/s with a spectral efficiency of 2.5 b/sample over a channel with a smooth magnitude response exhibiting 26 dB attenuation at half the sampling rate and a loss of 33 dB at 1/4 the data rate (i.e., the Nyquist rate of a 4-level pulse-amplitude modulated link at the same data rate). The proposed dynamic bit and power allocation method reduces the bit error rate from 3 × 10-3 to 2 × 10-5, measured with 23,265,420 bits.