Francisco C. B. F. Müller

A Front End for Discriminative Learning in Automatic Modulation Classification

This work presents a novel method for automatic modulation classification based on discriminative learning. The features are the ordered magnitude and phase of the received symbols at the output of the matched filter. The results using the proposed front end and support vector machines are compared to other techniques. Frequency offset is also considered and the results show that in this condition the new method significantly outperforms two cumulant-based classifiers.

Optimizing Power Normalization for G.fast Linear Precoder by Linear Programming

The use of vectoring for crosstalk cancellation in the new ITU-T G.fast standard for next generation DSL systems becomes essential for efficient utilization of the extended bandwidth (up to 200 MHz). In VDSL2 (up to 30 MHz), a zero-forcing-based linear precoder is used in downstream which approaches single-line performance. However, at high frequencies, the linear precoder may amplify the signal power substantially since the crosstalk channel is much stronger than at lower frequencies. Performance could be significantly degraded by power normalization to keep the PSD below the mask. In this work, we extended a per-line power normalization scheme by linear programming (LP) optimization. By simulations using measured cable data it is shown how the LP-based scheme further improves the linear precoder and it is also capable of balancing the data rate between lines. Further, the simulations also show the non-linear Tomlinson-Harashima precoder performs better than the linear precoders.

Capacity of MIMO DSL systems using 100 MHz measured channel data

This paper evaluates the capacity of MIMO DSL systems up to 100 MHz using short loops (50 and 200 meters) based on measured channel data. The experimental results show that these systems have capacities as high as 0.77 Gbps for the 50 m loop, for example.

Automatic modulation classification for cognitive radio systems: Results for the symbol and waveform domains

This work presents two approaches to the problem of automatic modulation classification in cognitive radios. The first approach deals with classifying distinct QAM modulations. The proposed solution consists of a SVM classifier that uses as input parameters the distance between the received symbol and its nearest neighbor in each constellation. The results obtained by the proposed classifier is compared to a state-of-art technique. The comparison show a good performance for the 16-QAM, 32-QAM and 64-QAM modulation schemes. In the second approach, the cyclic spectral analysis is adopted as the method for extracting the signals features, and the SVM classifier is used for the pattern recognition stage. The proposed method achieved excellent results for the AM, BPSK, QPSK and BFSK modulation schemes. In both approaches, different scenarios are evaluated which may serve as a starting point for researchers who want to compare results systematically.

Measurement and Modeling Techniques for the Fourth Generation Broadband Over Copper

Digital subscriber lines (DSL), the broadband data transmission technologies that use the copper cable as channel, are the most used Internet media around the world with more than 300 million users (Oksman et al., 2010), Much of the DSL success is related to the cost-benefit for both operators and served consumers. As the transmission channel is the common copper twisted-pair telephone cable, there is no need for large investments in infrastructure, because the telephone network is largely consolidated and active in almost all the world.

Performance Analysis of a Multiband OFDM UWB System in the Presence of Narrowband Interference

This paper presents a performance analysis of an ultra wideband (UWB) communication system based on Multiband Orthogonal Frequency Division Multiplexing (MB-OFDM) in the presence of narrowband interference. Although OFDM-based systems are known to be capable of withstanding some level of narrowband interference, mitigation techniques may have to be used when interference levels are high. Furthermore, as typical UWB systems employ low resolution analog-to-digital converters, the effect of narrowband interference may be exacerbated in the process of analog-to-digital conversion. In order to improve the performance of MB-OFDM UWB systems in the presence of narrowband interference, we consider the use of analog notch filters. This paper proposes an analytical model and formulation that allows for the evaluation of the probability of symbol error of an MB-OFDM UWB system when an analog notch filter is used for narrowband interference mitigation. It is shown that using an analog notch filter can significantly improve the performance of MB-OFDM UWB systems in high-interference scenarios.

DSL Impulse Noise Measurement System Implemented in USRP and GNU Radio

This paper describes an impulse noise measurement system for digital subscriber line channels composed by open hardware/software elements developed using the universal software radio peripheral and GNU is not Unix Radio. The proposed system proved to be capable of digitizing real occurrences of impulse noise. The goal is to use such system in large scale measurement campaigns, and then derive stochastic models for behavioral description of impulse noise. These models will provide better methods to reduce impulse noise effects, ever improving the quality of service in digital subscriber line transmissions.

Simulation and analysis of the impulsive noise effects in DSL video using Ptolemy II

This work presents the simulation and analysis of the impact of impulsive noise on video transmission over ADSL using the Ptolemy II framework. The implemented software modem includes channel coding and modulation used in the ADSL standard and an impulsive noise channel model. In the results, the effect of the use of different interleaver depth values in video transmission is evaluated using two different metrics: peak signal-to-noise ratio and double stimulus impairment scale.