Optimized Resource Allocation for Upstream Vectored DSL Systems With Zero-Forcing Generalized Decision Feedback Equalizer

Iterative Receiver Based on SAGE Algorithm for Crosstalk Cancellation in Upstream Vectored VDSL

“…This alien crosstalk manifests itself as spatially correlated (i.e., correlated across TPs) additive noise at each tone at the receiver of the considered VDSL system and hence degrades its performance even with the effective cancellation of self-crosstalk. Modeling of alien crosstalk is discussed in [3,10]. Alien crosstalk is easily amenable in the vectoring framework (due to the spatial correlation between different noise samples across the TPs).…”

“…The presence of an alien noise, originating from an external source, introduces a high spatial correlation among noise at the receivers of different vectored users [10][11][12]. It was shown in [3] that noise correlation between twisted pairs is more than the correlation between the tones.…”

“…However, the prewhitening operation applied on the spatially correlated noise destroys the columnwise diagonal dominant (CWDD) characteristics of the channel (leading to poor performance of linear receivers for alien crosstalk cancellation). The authors in [10] suggested a nonlinear successive interference canceler to achieve higher data rates than ZF receiver. However, this receiver requires QR (here Q denotes a unitary matrix, and R is an upper triangular matrix) decomposition of the channel matrix and is quite involved computationally because of the search required for QR ordering.…”

Performance analysis of a common-mode signal based low-complexity crosstalk cancelation scheme in vectored VDSL

“…Recently, an iterative receiver based on the SAGE algorithm has been proposed in [9] to eliminate the channel matrix inversion requirement of the ZF receiver while achieving near-optimal performance. When alien crosstalk is present, it is clear that various linear and non-linear receivers can be readily applied after a pre-whitening filter (see [9,10], and references therein). It is noted that noise is spatially correlated across TPs due to the introduction of crosstalk from an alien source [3].…”

“…When the ZF-based receiver [8] is applied after noise whitening, it suffers from a significant performance loss due to the ill-conditioning of the channel after the whitening process as discussed in [11]. Chen et al [10] have shown that a non-linear DFE-ZF can achieve data rate higher than a ZF receiver, though with an increase in computational complexity. In our previous study [9], we have shown that the SAGE based iterative receiver can effectively cancel the alien crosstalk to achieve a higher rate (with a little extra complexity).…”