Crosstalk Cancellation Research Articles

The ITU-T's new G.fast standard brings DSL into the gigabit era

This article explores the recently issued ITU-T Recommendations specifying (G.9701 [1] and G.9700 [2]) that bring user bit rates up to 1 Gb/s over twisted pairs from the distribution point to customer premises. The overview and some key research challenges of G.fast are discussed in [3]. The standardized G.fast transmission method and advanced crosstalk cancellation techniques are presented here with specific performance projections and measurement results achieved during the first demonstrations and trials, showing bit rates of 500 Mb/s over 250 m and available reach up to 400 m. A description of standardized tools for dynamic performance maintenance, resource allocation, and power saving enhancing G.fast applications concludes this article.

10 Gb/s adaptive receive-side merged near-end and far-end crosstalk cancellation circuitry in 65 nm CMOS

Crosstalk between neighboring channels can have significant impact on system bit-error rate (BER) as serial I/O data rates scale above 10 Gb/s. This paper presents receive-side circuitry which merges the cancellation of both near-end and far-end crosstalk (NEXT/FEXT) and can automatically adapt to different channel environments and variations in process, voltage, and temperature. NEXT cancellation is realized with a novel 3-tap FIR filter which combines two traditional FIR filter taps and a continuous-time band-pass filter IIR tap for efficient crosstalk cancellation, with all filter tap coefficients automatically determined via an on-die sign---sign least-mean-square (SS-LMS) adaptation engine. FEXT cancellation is realized by coupling the aggressor signal through a differentiator circuit whose gain is automatically adjusted with a power-detection-based adaptation loop. A prototype fabricated in a general purpose 65-nm CMOS process includes the adaptive NEXT and FEXT circuitry, along with a continuous-time linear equalizer (CTLE) to compensate for frequency-dependent channel loss. Enabling the crosstalk cancellation circuitry while operating at 10 Gb/s over coupled 4-in FR4 transmission line channels with NEXT and FEXT aggressors opens a previously closed eye and allows for a 0.2 UI timing margin at a BER = 10ź9. Total power including the NEXT/FEXT crosstalk cancellation circuitry, CTLE, and high-speed output buffer is 34.6 mW, and the core circuit area occupies 0.3 mm2.

Reflective Crosstalk Cancellation in Self-Seeded WDM PON for Mobile Fronthaul/Backhaul

Due to its large capacity and low latency, wavelength-division-multiplexed passive optical network (WDM PON) using self-seeded reflective semiconductor optical amplifier (RSOA) is an attractive, low-cost solution for mobile fronthaul/backhaul. However, multiple reflections in self-seeding cavity lead to reflective crosstalk, degrading its transmission performance. In this paper, reflective crosstalk in self-seeded RSOA under different bias conditions is experimentally characterized by its pulse response, and then novel feedforward and feedback approaches are proposed to suppress the reflective crosstalk in self-seeded WDM PON. Experimental results using a simple delay and differentiation method show significant reduction in the reflective crosstalk for self-seeded RSOA. With the proposed feedforward crosstalk cancellation, 2.5-Gb/s mobile backhaul using self-seeded RSOA achieves 1.7-dB performance improvement after transmission over 20-km single-mode fiber. In addition, low-cost bandwidth-efficient mobile fronthaul for 24 20-MHz LTE signals is demonstrated using a self-seeded RSOA with only 1.5-GHz bandwidth. With adaptive feedback crosstalk cancellation, the error vector magnitude for the received LTE signal after 20-km standard single-mode fiber transmission in the C-band is improved by 20%.

Implementation Analysis of Binaural Audio Crosstalk Cancellation on Heterogeneous Parallel Computing platforms using Mixed Non-Uniform Partitioned Convolution

As general DSP processor architectures don’t have massive parallel architecture, they are not suitable to implement 3D audio virtual techniques at very long filters due to computational problems. To address these implementation issues of very long filters, an efficient method called Mixed Non-uniform Partitioned Convolution is proposed in this paper for implementing binaural audio crosstalk cancellation on heterogeneous parallel computing platforms. By using massive parallel architecture of heterogeneous platforms, the proposed approach is able to solve computational problems even at filter lengths of 65536 (32-bit floating point). The partitioning scheme followed in this paper is explained in detail to schedule partitions on various compute units of GPU device. The proposed approach was implemented on AMD GPUs using task parallel concept. The instruction level optimization was also provided for complex frequency multiplication and addition using OpenCL. The performance of this approach is compared against the existing techniques proposed by Garcia and Gardener. The cost vs. computational performance tradeoff comparison was given between proposed approach and existing methods. The comparison clearly shows that proposed approach is very efficient at very long filters and requires reasonable cost of implementation in terms of number of compute units. The combination of instruction level and algorithmic level optimizations make the proposed approach more suitable for implementation of not only stereo inputs based audio CTC but also multichannel inputs, particularly at very long filter lengths on parallel computing platforms.

A Linear Robust Binaural Sound Reproduction System with Optimal Source Distribution Strategy

Crosstalk cancellation system plays an important role in binaural sound playback using loudspeakers and has attracted many researchers' interest. However, limited sweet spot is still a challenge especially when the head is laterally misaligned. In this report the optimization of a linear binaural playback system is proposed, in which the optimal source distribution strategy in a linear array configuration is combined with the technique of multiple control points. The proposed method aims to find a good trade-off between the crosstalk cancellation performance and the robustness against the head misalignment. Both simulations and experiments demonstrate the efficacy of the proposed method.

Adaptive Techniques for Joint Optimization of XTC and DFE Loop Gain in High-Speed I/O

High-speed I/O channels require adaptive techniques to optimize the settings for filter tap weights at decision feedback equalization (DFE) read channels to compensate for channel inter-symbol interference (ISI) and crosstalk from multiple adjacent channels. Both ISI and crosstalk tend to vary with channel length, process, and temperature variations. Individually optimizing parameters such as those just mentioned leads to suboptimal solutions. We propose a joint optimization technique for crosstalk cancellation (XTC) at DFE to compensate for both ISI and XTC in high-speed I/O channels. The technique is used to compensate for between 15.7 dB and 19.7 dB of channel loss combined with a variety of crosstalk strengths from to adaptively, where the transmit non-return-to-zero signal amplitude is a constant .

Investigating a Guard Trace Ring to Suppress the Crosstalk due to a Clock Trace on a Power Electronics DSP Control Board

The grounded guard trace ring is usually utilized to suppress the interference in high-speed printed circuit boards or IC packages. Although the guard ring can reduce crosstalk, its performance is greatly affected by the effectiveness of its design. This paper first investigates the mechanism of the crosstalk cancelation with a grounded guard ring. The paper then discusses and analyzes several grounding patterns based on a lumped circuit model. The analysis applies to the applications where the dimensions of PCB traces are smaller than 5% of the wavelength at the highest frequency. It is found that the best grounding patterns for the guard trace ring is to ground its two ends instead of using multipoint grounding within the concerned frequency range from 10 to 200 MHz in this paper. The theoretical analysis and the developed technique are verified by electromagnetic field distribution plots and the four-ports scattering parameters that are simulated in ANSYS HFSS 3-D electromagnetic simulation software. Experiments were finally conducted to validate the analysis and the proposed technique.

Design and Implementation Analysis of OSD based Audio Crosstalk Cancellation with Multi-Channel Inputs on DSP Processors

To overcome the basic system inversion problems in conventional crosstalk cancellation systems, the three channel Optimum Source Distribution (OSD) was developed by Takashi et al., that provides balance between in-phase and out of phase components. The main difficulty in this system is real-time implementation of cross talk cancellation filters on DSP platforms, particularly when filter lengths are very long with system operates on multichannel inputs. This paper discusses the implementation complexities and proposes an efficient approach to reduce the power consumption. It also discusses efficient usage of available processor memory. By utilizing the processor resources and existing frequency domain techniques, this approach would be one of best methods for long filters. The mathematical model, with efficient design for floating point DSP processors, clearly explains the optimization methods at algorithmic and instruction levels. The computational complexity of the proposed method was measured for various multi-channel input sources and the comparison was shown. The results indicate that the proposed method provides efficient computations than existing methods. Keywords: Convolution, Crosstalk Cancellation, Optimal Source Distribution, Overlap Save Method, Uniform Partitioned Convolution

CROSSTALK CANCELLATION METHOD BASED ON UNITARY TRANSFORMATION OF COUPLED TRANSMISSION LINES-CHANNEL TRANSMISSION MATRIX

Crosstalk is one of the bottlenecks for high-speed circuits to increase its rate and density. In order to make tradeoff between complexity and effect of the crosstalk cancellation circuit, a crosstalk cancellation method based on unitary transformation is proposed. In the method, two unitary matrixes are obtained by Singular Value Decomposition (SVD) of coupled transmission lines-channel transmission matrix (CTL-CTM), and then according to the form of the unitary matrixes, the crosstalk canceling circuits are built at both ends of the transmission line, which could transform the CTMes into unit ones and crosstalk would be cancelled out. Circuit simulation results show that at the signaling rate of 5 Gbit/s, jitter performance of eye diagram improves 85% and vertical performance improves 77.5%, which means the method achieves better crosstalk canceling effect with lower circuit cost.

Performance Enhancement of Cross-Talk Canceller for Four-Speaker System by Selective Speaker Operation

Performance Enhancement of Cross-Talk Canceller for Four-Speaker System by Selective Speaker Operation

Development of dynamic crosstalk cancellation system for multiple-listener binaural reproduction

Development of dynamic crosstalk cancellation system for multiple-listener binaural reproduction

Increasing the transmission capacity of digital subscriber lines with phantom circuit and crosstalk cancelation

The technique of realizing phantom circuits in multi-pair and multi-quad metallic cables enables creating additional transmission circuits over standard pairs and quads in metallic cables. Theoretically, these phantom circuits can be subsequently used for additional digital subscriber lines and thanks to that the overall transmission capacity of metallic cables can be possibly increased. However, the transmission rates of present digital subscriber lines are limited mainly by physical parameters of used cables, such as attenuation and impedance, and also by the disturbances caused mainly by a crosstalk. One of the most promising solutions for full cancelation of far-end crosstalk is vector discrete multi-tone modulation (VDMT). First, this article contains brief introduction about the current situation in access networks, digital subscriber lines and metallic cables. Next, the practical experiment with metallic cable and necessary equipment was performed, the phantom circuit was created over one star-quad of a cable and its parameters and characteristics were measured and they are presented in the next section of this article. Based on these results, the next part is focused on the simulation of a modern digital subscriber line (VDSL2) using phantom circuit together with and without crosstalk elimination technique using VDMT modulation. The results and calculations of possible transmission capacity of phantom circuit are compared with measured results for two most frequently used VDSL2 profiles.

A 5 Gbps 1.6 mW/G bps/CH Adaptive Crosstalk Cancellation Scheme With Reference-less Digital Calibration and Switched Termination Resistors for Single-Ended Parallel Interface

A low power adaptive crosstalk cancellation for single-ended parallel interface is presented. A fast digital calibration which accurately detects the amount of crosstalk without a reference clock (reference-less) is proposed. To transfer calibration information from a receiver to a transmitter without additional channels, switched termination resistors (STR) are implemented. The reference-less adaptation and STR schemes achieve low power consumption and small area. A crosstalk compensator with simple structure is placed at transmitter-side, and it requires less design effort and low power. The proposed adaptive crosstalk cancellation scheme rapidly determines the optimum calibration point only during 4-cycle calibration time, and eliminates from 50% to 87.1% of the crosstalk-induced jitter (CIJ). It operates up to 5 Gbps consuming 1.6 mW/Gbps/CH in a 130 nm CMOS.

A Framework for the Calculation of Dynamic Crosstalk Cancellation Filters

Dynamic crosstalk cancellation (CTC) systems commonly find use in immersive virtual reality (VR) applications. Such dynamic setups require extremely high filter update rates, so filter calculation is usually performed in the frequency-domain for higher efficiency. This paper proposes a general framework for the calculation of dynamic CTC filters to be used in immersive VR applications. Within this framework, we introduce a causality constraint to the frequency-domain calculation to avoid undesirable wrap-around effects and echo artifacts. Furthermore, when regularization is applied to the CTC filter calculation, in order to limit the output levels at the loudspeakers, noncausal artifacts appear at the CTC filters and the resulting ear signals. We propose a global minimum-phase regularization to convert these anti-causal ringing artifacts into causal artifacts. Finally, an aspect that is especially critical for dynamic CTC systems is the filter switch between active loudspeakers distributed in a surround audio-visual display system with 360° of freedom of operator orientation. Within this framework we apply a weighted filter calculation to control the filter switch, which allows the loudspeakers' contribution to be windowed in space, resulting in a smooth filter transition.

Performance of Space–Time–Frequency Coding Over Indoor Power Line Channels

We present a multiple-input-multiple-output (MIMO) power line communication (PLC) system using coupled indoor differential mode ports, where 2 × 2 and 2 × 4 MIMO configurations are considered. In simulation, MIMO orthogonal frequency-division multiplexing (OFDM) PLC with the two OFDM symbol sequence reordering schemes, namely, Alamouti-scheme-based sequence reordering and circularly-shifted sequence reordering, is compared under the coupled channel conditions. For MIMO coding, we employ a maximum ratio combining scheme that is effective for both MIMO and single-input-single-output over indoor power line conditions. In simulation, we compare space-frequency coding (SFC), space-time coding (STC), and space-time-frequency coding (STFC) over statistical indoor power line channels, including fading, impulse noise, and crosstalk by coupling between ports. STFC and STC are more robust against crosstalk than SFC, and STFC, with some added complexity, outperforms the other coding schemes in terms of bit-error-rate performance. A least squares scheme for power line channel estimation is used, which is simple but has comparable performance to minimum mean square error. A decision-feedback-loop-based crosstalk cancellation scheme that effectively reduces the MIMO channel estimation error due to crosstalk is presented. Simulation results show that STFC is less sensitive to impulse noise than STC or SFC.

MIMO DWDM System Using Uncooled DFB Lasers With Adaptive Laser Bias Control and Postphotodetection Crosstalk Cancellation

A proof-of-principle demonstration of a multiple input-multiple output (MIMO) dense wavelength division multiplexing (DWDM) system is reported. It uses standard uncooled distributed feedback lasers with intensity modulation-direction detection (IM-DD), in which the temperature of each laser is allowed to drift independently within a 50 °C temperature range. A feedback-based laser bias control algorithm is introduced to guarantee acceptable wavelength spacing and a postphotodetection minimum mean square error decoder is applied to cancel the interchannel crosstalk. The relative sensitivity of the MIMO receiver in both a random laser temperature drift scenario and a worst-case scenario are investigated by simulations in MATLAB. Experimental results for a 40-channel × 12.5 Gb/s DWDM system transmitting over 28 km of single-mode fiber with worst possible wavelength distribution prove the feasibility of the technique.

Crosstalk cancelling voltage‐mode driver for multi‐Gbps parallel DRAM interface

SummaryFor multi‐Gb/s/pin parallel dynamic random access memory (DRAM) interface, a crosstalk cancelling voltage‐mode driver is proposed. The voltage‐mode driver is composed of a main driver and sub‐drivers where the cancellation signal is generated by the sub‐drivers. The outputs of the main driver and sub‐drivers are combined by a capacitive coupling so the direct current (DC) output swing is not affected by the crosstalk cancellation and the sub‐drivers may not consume DC power. The proposed crosstalk cancelling voltage‐mode driver implemented in a 0.11‐µm complementary metal‐oxide semiconductor (CMOS) technology improves the horizontal eye openings by 22.6 ps at 4‐Gbps/pin. Copyright © 2014 John Wiley & Sons, Ltd.

Adaptive acoustic crosstalk cancellation in mobile computer device

Wydawnictwo SIGMA-NOT wydaje czasopisma fachowe informujące swoich czytelników o najnowszych osiągnięciach naukowych i nowoczesnych rozwiązaniach technicznych w Polsce i na świecie, popularyzuje problemy techniczne oraz poszerza wiedzę i kulturę techniczną.

The role of interaural level differences in the localization of low-frequency sine tones

Five human listeners reported the azimuthal locations of low-frequency sine tones presented in free field, either by a 180-degree loudspeaker array or by virtual reality. The virtual sources were synthesized using cross-talk cancellation based on signals continuously monitored in the listener's ear canals. The experiment tested the duplex model of sound localization, especially the role of interaural level differences (fixed ILD = 0, 6, or 12 dB) for frequencies of 750 Hz or less. Trials with real sources, baseline virtual sources, and virtual sources with manipulated ILDs were always combined in all experiments. Experiments showed that the interaural time differences (ITD) dominated most fixed opposing ILDs, as previously reported, only when interaural phase differences (IPD) were less than 90 degrees. When IPDs exceeded 90 degrees, the ITD lost its influence, and localization was dominated by ILDs. Localization judgments never followed IPDs across a 180-degree boundary, except when a zeroed ILD caused judgments to become chaotic. Within the 90-degree IPD limit, judgments for fixed ILD appeared to follow the ITD better than the IPD. Abnormal interaural conditions (e.g., ITDs and ILDs of opposite sign) led to a notable increase in front-back confusions. [Work supported by AFOSR grant FA9550-11-1-0101.]

Crosstalk reduction in stereoscopic 3D displays: Disparity adjustment using crosstalk visibility index for crosstalk cancellation

Stereoscopic displays provide viewers with a truly fascinating viewing experience. However, current stereoscopic displays suffer from crosstalk that is detrimental to image quality, depth quality, and visual comfort. In order to reduce the perceived crosstalk in stereoscopic displays, this paper proposes a crosstalk reduction method that combines disparity adjustment and crosstalk cancellation. The main idea of the proposed method is to displace the visible crosstalk using the disparity adjustment in a way that less amounts of intensity leakage occur on perceptually important regions in a scene. To this purpose, we estimate a crosstalk visibility index map for the scene that represents pixel-by-pixel importance values associated with the amount of perceived crosstalk and negative-after-effects of the crosstalk cancellation. Based on the crosstalk visibility index, we introduce a new disparity adjustment method that reduces the annoying crosstalk in processed images, which is followed by the crosstalk cancellation. The effectiveness of the proposed method has been successfully evaluated by subjective assessments of image quality and viewing preference. Experimental results demonstrate that the proposed method effectively improves the image quality and overall viewing quality of stereoscopic videos.