Intra-Symbol Windowing for Egress Reduction in DMT Transmitters

Abstract

Discrete multitone (DMT) uses an inverse discrete Fourier transform (IDFT) to modulate data on the carriers. The high sidelobes of the IDFT filter bank used can lead to spurious emissions (egress) in unauthorized frequency bands. Applying a window function within the DMT symbol can alleviate this. However, window functions either require additional redundancy or will introduce distortions that are generally not easy to compensate for. In this paper, a special class of window functions is constructed that corresponds to a precoding at the transmitter. These do not require any additional redundancy and need only a modest amount of additional processing at the receiver. The results can be used to increase the spectral containment of DMT-based wired communications such as ADSL and VDSL (i.e., asymmetric, resp., very-high-bitrate digital subscriber loop).

Spectrum sidelobe suppression for discrete Fourier transformation-based orthogonal frequency division multiplexing using adjacent subcarriers correlative coding

“…The spectrum of OFDM signal based on analogue representation is used by Brandes et al [5] and Cosovic et al [9], but the spectrum in this simulation is based on (7). Note that the idea of subcarrier weighting does not depend on the spectrum model.…”

“…Note that the idea of subcarrier weighting does not depend on the spectrum model. In addition, |H(jV)| 2 is also shown in the figure for illustrating (7) which is the PSD of the continuous baseband OFDM signal. It is assumed that the CP length is N/8 and the original data c (l) n 's are quadrature phase shift keying (QPSK)-mapped.…”

“…To mitigate this problem, many methods have already been employed, such as the insertion of guard subcarriers [4] or cancellation subcarriers [5], windowing (in time domain) [6,7] and using various pulse-shaping filter or filtering before transmitting [8]. It is known that the guard subcarriers decrease the spectral efficiency, whereas windowing reduces the delay spread tolerance and filtering is more complex with latent defect of distorting the wanted signals.…”

Pairwise subcarriers weighting for suppressing out‐of‐band radiation of OFDM

“…To mitigate the OOB radiation problem, several methods have been applied to the pulse‐shaped OFDM previously, such as the insertion of guard subcarriers , windowing (in time domain) , and filtering (in frequency domain) . It is known that the guard subcarriers decrease the spectral efficiency, that the windowing reduces the multipath delay tolerance, and that the filtering is more complex with a latent of distorting the transmitted signals.…”