Reduction of guard interval by impulse compression for DMT modulation on twisted pair cables

Abstract

In multicarrier modulation schemes like Orthogonal Frequency Division Multiplex (OFDM) or Discrete Multi Tone (DMT) a guard interval represented by a cyclic prefix (CP) is inserted between successive multicarrier symbols in order to reduce intersymbol interference (ISI). The length of the guard interval is determined by the length of the channel impulse response (CIR).For a fixed guard interval, the longer the CIR, the higher the IS1 is. In this paper, we have designed a time domain equalizer (TEQ) to compress the impulse response of several twisted pair lines with and without bridged taps. The reduction of IS1 is shown as well as the resulting signal to noise ratio (SNR) in the presence of white Gaussian noise, near and far end crosstalk (NEXT, FEXT) for various equalizer designs.

Unification and evaluation of equalization structures and design algorithms for discrete multitone modulation systems

“…Alternatively, one can maximize the windowed energy, while constraining the wall energy, as suggested in [60] and later in [61]. Since H T wall H wall is always positive definite when L h ≥ ν + 1, the latter approach is preferred and reduces to solving (2) with…”

Free-Space Optical Communications with Channel Shortening Filter and Viterbi Equalizer

“…An alternative TEQ solution is maximum-shortening SNR (MSSNR) TEQ criterion [10,11]. Its philosophy can be explained by Eq.…”

“…In this paper, as an alternative, we propose an FSO system for through-cloud communications consisting of a channel shortening equalizer [10][11][12] followed by a Viterbi equalizer [13]. TEQ was originally proposed to reduce the length of the discrete channel impulse response (CIR) in channels such as digital subscriber loop (DSL) or cable.…”

“…In this paper, the authors will use two well-known CIR shortening algorithms, maximum shortened signal-to-noise ratio (MSSNR) [10,11] and MMSE [12], followed by the MLSD algorithm to evaluate error performance of FSO in airto-ground through-cloud channel. FSO channel model reported in [2] will be adopted.…”

Linear Phase Impulse Response Shortening for xDSL DMT modems

“…One of the main issues in the xDSL systems is the severe attenuation and distortion caused by the channel and other services on the same bundle. To overcome these channel effects on the transmitted signals, equalisation techniques are commonly used in time [4], [5], [6], [7], [8] and frequency [9] domain. The equalisation process can be simplified by periodically extending each symbol with a convenient number of prefix and suffix samples [1].…”