Crosstalk Models for Short VDSL2 Lines from Measured 30 MHz Data

IEEE Trans. Signal Process.

Sidiropoulos

2009

Crosstalk interference is the limiting factor in transmission over copper lines. Crosstalk cancelation techniques show great potential for enabling the next leap in DSL transmission rates. An important issue when implementing crosstalk cancelation techniques in hardware is the effect of finite world length on performance. In this paper we provide an analysis of the performance of linear zero-forcing precoders, used for crosstalk compensation, in the presence of finite word length errors. We quantify analytically the trade off between precoder word length and transmission rate degradation. More specifically, we prove a simple formula for the transmission rate loss as a function of the number of bits used for precoding, the signal to noise ratio, and the standard line parameters. We demonstrate, through simulations on real lines, the accuracy of our estimates. Moreover, our results are stable in the presence of channel estimation errors. Finally, we show how to use these estimates as a design tool for DSL linear crosstalk precoders. For example, we show that for standard VDSL2 precoded systems, 14 bits representation of the precoder entries results in capacity loss below 1% for lines over 300m.

“…We have used the results of the measurement campaign conducted by France Telecom R&D as described in [10]. All experiments used the band 0 − 30 MHz.…”

Section: Simulation Resultsmentioning

confidence: 99%

“…Next we used (12) to fit the parameter α of the cable via the measured insertion losses. The process of fitting is described in detail in [10]. Its value which was used in the bound (59) was α = 0.0019.…”

Section: Full Bandmentioning

confidence: 99%

Finite Word Length Effects on Transmission Rate in Zero Forcing Linear Precoding for Multichannel DSL

Sayag

IEEE Trans. Signal Process.

Sidiropoulos

2009

“…Calculating the achievable user rate, and maximizing over all users results in (16). The second inequality, (17), results from definitions (9) and (11), which guarantee that β D,max ≥ β row .…”

Section: Downstream Boundsmentioning

confidence: 99%

The Performance of Zero Forcing DSL Systems

Bergel

IEEE Signal Process. Lett.

2013

DSL systems use multi-channel processing to mitigate the electromagnetic coupling between the wires in a binder and provide high data rates to multiple users. In recent years, most multichannel processing for DSL had focused on zero-forcing (ZF) processing that was proven to be near optimal.This near optimality has been observed in numerical evaluations as well as in real life systems. However, this near optimality has only been demonstrated theoretically by relatively loose bounds. In this paper we prove novel bounds on the performance of ZF processing in DSL systems. These bounds are simpler and yet tighter than currently known bounds. These novel bounds support previously published results, and further confirm the near optimality of ZF processing.

“…Insertion loss (IL) decays more gracefully with frequency at these lengths, potentially supporting transmission over up to 30 MHz for the shorter loops, which is 50% more than in VDSL 998. At the same time, far-end crosstalk (FEXT) becomes more prominent at these shorter loop lengths -e.g., at 75m, FEXT behaves quite similarly to near-end crosstalk (NEXT), as is intuitive [7]. For this reason, coordinated (also known as vectored) multiple -input multiple -output (MIMO) transmission [5] becomes even more important in this context.…”

Section: Introductionmentioning

confidence: 87%

Capacity statistics for short DSL loops from measured 30 MHz channel data

Karipidis

Sidiropoulos

IEEE 6th Workshop on Signal Processing Advances in Wireless Communications, 2005.

et al.

-In recent years, there is growing interest in hybrid fiber-copper access solutions, as in fiber to the basement (FTTB) and fiber to the curb/cabinet (FTTC), combined with advanced vectored transmission modalities. The twisted pair segment in these architectures is in the range of a few hundred meters, thus supporting transmission over up to 30 MHz. In this paper, we assess the capacity potential of these very short loops using full-binder channel measurements collected by France Telecom R&D. Key statistics are provided for both uncoordinated and vectored transmission, and the vectoring benefit is evaluated. The results provide useful bounds for developers and providers alike.