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At present, Discrete Multi-Tone (DMT) transceivers receive much attention for the implementation of Asymmetric Digital Subscriber Lines (ADSL). This paper analyzes the effect of clipping a DMT-signal, i.e. limiting the signal's maximum amplitude. An exact expression is given for the signal-to-noise ratio ( S N . ) degradation due to clipping alone. By combining this expression with the well-known expression for the quantization noise in the AID-DIA converters, it is shown how clipping can reduce the number of bits of AID-DIA converters as well as the dynamical range of the line drivers while keeping the overall SNR the same as without clipping.

A new selected mapping orthogonal frequency division multiplexing modulation (SLM-OFDM) that generates (U 2 /4) symbol candidates using U inverse fast Fourier transform is presented. The complementary cumulative distribution function of peak-to-average power ratio (PAPR) of the so-called GreenOFDM is derived and computer simulations show that the proposed method outperforms any other SLM-OFDM proposed method so far. Also, GreenOFDM is compared with localised single carrier frequency division multiple access as it is a well-known PAPR reduction technique standardised for long-term evolution advanced.

We overview a digital duplex scheme called Zipper, intended for DMT-based VDSL systems. The Zipper multicarrier duplex scheme represents a breakthrough toward digital implementation of frequency-division duplexing. A duplex scheme is a method to divide the capacity of a line between the upstream and downstream directions. Zipper divides the available bandwidth by assigning different subcarriers for the different directions. As a prerequisite, DMT symbols are extended with an additional cyclic suffix, and are shaped at both transmitter and receiver. Zipper is characterized by high flexibility and high spectral compatibility with programmable spectrum usage, robustness against frequency-selective impairments such as radio frequency interference and bridge taps, interoperability with ADSL, and high spectral efficiency since no guard bands are needed.

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