Linear IIR Precoding to Shorten the Cyclic Prefix in Wireline Multitone Systems

F.J. Simois and J.I. Acha (Spain)


OFDM Technology, precoding, DSL.


Discrete multitone (DMT) systems need the use of a guard interval, known as cyclic prefix (CP), to avoid intersymbol interference (ISI) and interchannel interference (ICI). Unfortunately, this prefix produces a decrease in the achievable bandwidth efficiency. To deal with this problem, we present in this paper an IIR linear precoder that adds memory in the time-domain, reducing the length of the guard time to only the maximum-phase component of the channel. It is shown that the received signal with this precoder and the received signal in a DMT system that uses CP are identical, so perfect reconstruction is possible in a noise-free situation. In addition, the behavior of this scheme in presence of noise is the same as in a DMT system with CP, allowing the use of bit and power loading algorithms. Unlike other previous IIR precoders, this one has not convergence problems. As an example, it is shown its good performance in an ADSL environment.

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