ADSL, VDSL, and Multicarrier Modulation: Wiley Series in Telecommunications and Signal Processing
ADSL, VDSL, and Multicarrier Modulation: Wiley Series in Telecommunications and Signal Processing
A semi-blind channel estimation method for multiuser multiantenna OFDM systems
IEEE Transactions on Signal Processing
A comparison of pilot-aided channel estimation methods for OFDMsystems
IEEE Transactions on Signal Processing
Exploiting input cyclostationarity for blind channel identificationin OFDM systems
IEEE Transactions on Signal Processing
Vectored transmission for digital subscriber line systems
IEEE Journal on Selected Areas in Communications
ICC'09 Proceedings of the 2009 IEEE international conference on Communications
An SNR-assisted crosstalk channel estimation technique
ICC'09 Proceedings of the 2009 IEEE international conference on Communications
Adaptive precoding for downstream crosstalk precancelation in DSL systems using sign-error feedback
IEEE Transactions on Signal Processing
On signal-to-noise ratio-assisted crosstalk channel estimation in downstream DSL systems
IEEE Transactions on Signal Processing
EURASIP Journal on Advances in Signal Processing
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With increasing bandwidths and decreasing loop lengths, crosstalk becomes the main impairment in VDSL systems. For downstream communication, crosstalk precompensation techniques have been designed to cope with this issue by using the collocation of the transmitters. These techniques naturally need an accurate estimation of the crosstalk channel impulse responses. We investigate the issue of tracking these channels. Due to the lack of coordination between the receivers, and because the amplitude levels of the remaining interference from crosstalk after precompensation are very low, blind estimation schemes are inefficient in this case. So some part of the upstream or downstream bit rate needs to be used to help the estimation. In this paper, we design a new algorithm to try to limit the bandwidth used for the estimation purpose by exploiting the collocation at the transmitter side. The principle is to use feedback from the receiver to the transmitter instead of using pilots in the downstream signal. It is justified by computing the Cramer-Rao lower bound on the estimation error variance and showing that, for the levels of power in consideration, and for a given bit rate used to help the estimation, this bound is effectively lower for the proposed scheme. A simple algorithm based on the maximum likelihood is proposed. Its performance is analyzed in detail and is compared to a classical scheme using pilot symbols. Finally, an improved but more complex version is proposed to approach the performance bound.