We consider a bit-interleaved coded wideband impulse-modulated system for power line communications. Impulse modulation is combined with direct-sequence code-division multiple access (DS-CDMA) to obtain a form of orthogonal modulation and to multiplex the users. We focus on the receiver signal processing algorithms and derive a maximum likelihood frequency-domain detector that takes into account the presence of impulse noise as well as the intercode interference (ICI) and the multiple-access interference (MAI) that are generated by the frequency-selective power line channel. To reduce complexity, we propose several simplified frequency-domain receiver algorithms with different complexity and performance. We address the problem of the practical estimation of the channel frequency response as well as the estimation of the correlation of the ICI-MAI-plus-noise that is needed in the detection metric. To improve the estimators performance, a simple hard feedback from the channel decoder is also used. Simulation results show that the scheme provides robust performance as a result of spreading the symbol energy both in frequency (through the wideband pulse) and in time (through the spreading code and the bit-interleaved convolutional code).

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Wideband Impulse Modulation and Receiver Algorithms for Multiuser Power Line Communications

In this paper, we address the general issue of asynchronous impulsive noise mitigation and its application over coded power-line communications (PLC). As is well known, PLC channels usually suffer from significant degradation due to impulsive interference generated by electrical appliances. The use of a level limiter is a simple and intuitive technique, widely used to mitigate the noxious effect of impulsive noise in these channels. However, the determination of the clipping threshold remains, most of the time, empirical, and the impulse statistics are usually assumed to be known. In a previous study, we proposed an original threshold determination based on signal detection theory, using the well-known false alarm and good detection tradeoff. Here, we further investigate the proposed optimization method in closed form. We compare two tradeoff criteria by means of a receiver operating curves analysis. We clearly show that the resulting decision fits well with encountered bit-error rate performances. We also evaluate the influence of impulsive noise statistics estimation on the performance of the proposed approach. To do so, we assess the robustness of the classical method of moments on Gaussian mixture estimation. It clearly appears that the estimation method is reliable for reasonable values of the impulse occurrence. As one of the main results of this paper, we make a proposal for impulse statistics estimation under ?severe? conditions (i.e., for very rare impulse events, based on impulse detection over corrupted OFDM symbols). Subsequently, we propose a general scheme of automatic impulse mitigation, according to the disturbance ratio of the environment. Finally, the performance of the approach is evaluated over the Home-Plug AV (HPAV) physical layer.

Adaptive Noise Mitigation in Impulsive Environment: Application to Power-Line Communications

Power-line communications (PLC) have gained a lot of scientific interest over the past years. In this paper, a practical noise model is proposed that best describes the noise conditions on an orthogonal frequency-division multiplexing PLC system. The noise present on a power-line system is divided in five categories which are grouped into two classes: 1) the generalized background and 2) the impulsive noise. In this paper, all of the components comprising the noise are precisely depicted on a computer simulation system. The statistical properties regarding all component parameters are taken into account and used in our model. By this way, the real conditions on a PLC channel can be portrayed in the most precise way. This model is tested on a PLC channel and its performance in terms of bit-error rate versus the E b/N 0 value is obtained. For reasons of completeness, we examine how two of the model's components affect the system's performance by altering their vital parameters. In order to accomplish this, we take various values for these parameters and we check their influence on the system. Furthermore, we apply a popular noise model, such as Middleton's noise model and we compare the performance obtained by both noise models.

Modeling the Noise on the OFDM Power-Line Communications System

In this paper, we investigate the ultimate performance limits, in terms of achievable information rate (IR), of communication systems impaired by impulse noise. We compare single carrier (SC) and multi-carrier (MC) transmission systems employing quadrature amplitude modulation (QAM) formats. More precisely, we consider SC schemes with coded modulations and MC systems based on orthogonal frequency division modulation (OFDM). For the MC schemes, we introduce a theoretically equivalent channel model which makes the computation of the IR feasible. This simple channel model will be referred to as interleaved MC. We show that, in the presence of impulse noise and except for systems operating at very high spectral efficiency, the IR of MC schemes is lower than that of SC schemes. More precisely, use of MC schemes may lead to an unavoidable fundamental loss with respect to SC schemes at typical coding rates, whereas MC schemes are to be preferred for very high coding rates or in uncoded systems. These results hold for additive white Gaussian noise (AWGN) and dispersive channels, either considering plain OFDM or MC schemes employing water-filling and bit-loading algorithms. In order to validate our theoretical results, we also obtain the bit error rate (BER) performance of SC and MC schemes through Monte Carlo simulations. A few trellis-coded modulation (TCM) and low-density parity-check (LDPC)-coded schemes are considered. The obtained SNR loss in the BER curves between the AWGN and impulse noise channels matches well with the corresponding IR gap.

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Fundamental performance limits of communications systems impaired by impulse noise

Power line channel often suffers from impulsive interference generated by electrical appliances. Therefore, power line communication makes degradation due to such impulsive interference. We introduce Middleton's class a noise model into a statistical model of impulsive noise environment. In this paper, we apply LDPC (low density parity check) codes and sum-product decoding to additive white class a noise (AWAN) channels. We propose a sum-product decoding which is suitable for AWAN channels. In addition, we show the BER (bit error rate) performance of the proposed sum-product decoding in class a noise environment by computer simulation.

A decoding for low density parity check codes over impulsive noise channels

Power line channels often suffer from impulsive interference generated by electrical appliances. Therefore, power line communication (PLC) degrades due to such impulsive interference. Middleton's class A noise model is frequently utilized for the modeling of such impulsive noise environments. We deal with turbo decoding for turbo codes over an additive white class A noise (AWAN) channel. We propose a turbo decoding which is suitable for AWAN channels. In addition, we show the BER (bit error rate) performance of the proposed turbo decoding in a class A noise environment by computer simulation.

Turbo decoding in impulsive noise environment

Power lines are one of the most attractive communication media for access and/or in-home networks. The regulations on power line communication (PLC) may be eased in Japan and we could utilize a frequency band from 2 to 30 MHz in the future. However, this frequency band often suffers from narrowband interference caused by amplitude modulated (AM) broadcasting and/or amateur ham radio. The narrowband interference level may be much higher than the background noise if the interference source is close enough. Therefore, modulation and coding over power line channels are required to have immunity to narrowband interference. Multicarrier modulation (MCM) is expected as one of modulation methods which are robust to narrowband interference. In this paper, we investigate two MCMs, one is OFDM (Orthogonal Frequency Division Multiplexing) with windowing whose window type is a raised cosine window and the other is CMFB (Cosine-Modulated Filter Bank) based transmultiplexer, under narrowband interference environments. We compare the performances of these two MCMs over narrowband noise channels by computer simulations. As these results, we show that CMFB transmultiplexer has a better performance than OFDM with windowing under narrowband noise environments.

Performance Evaluation of CMFB Transmultiplexer for Broadband Power Line Communications under Narrowband Interference

Residential power lines are one of the most attractive communication media for home networking, since every room in a house has multiple power outlets. In general, in-home power line networks have various network components which are not related to communications. The power line network includes many electrical appliances without communication facilities, switches, and so on. These components will cause electrical unbalance of the power line network and increase radiated emissions. We investigate that each power line network component has an impact on the electrical unbalance and the radiated emissions quantitatively by an experiment. As the result, we show that the radiated emissions and the electrical unbalance of the network vary significantly as the wired network components. Furthermore, our result indicates that the radiated emission is especially large in the case where the network contains a fluorescent light or a single-pole switch.

The Correlation between Radiated Emissions and Power Line Network Components on Indoor Power Line Communications

@imc.cce.i.kyoto-u.ac.jpResidential power line is one of the most attractive com-munication media for in-home networking, since almost allrooms in a house have power outlets. The regulations onpower line communication (PLC) may be eased in Japanand we could utilize a frequency band from 2 to 30MHzin the future. However, many electrical appliances and/orshortwave systems frequently cause man-made electromag-netic interference on indoor power line. This man-madenoise often has impulsive characteristics. We will extendknowledge about impulse noise at indoor power line in thefrequency range from 2 to 30MHz. We measure indoorpower line noise in several environments and apply a de-tection method by chi-square test to the measured noise.Further we model the amplitudes, durations, and interar-rival time of indoor power line impulses. These impulsenoise models are expected to utilize for communication de-sign about PLC.1. INTRODUCTIONIn-home PLC is getting so much attention for in-homenetworking, since almost all rooms in a house have poweroutlets. Therefore a relaxation of the regulations on PLC isdiscussed and we could utilize a frequency band from 2 to30MHz in the future. However many electrical appliancesand/or shortwave systems frequently cause man-made elec-tromagnetic noise on indoor power line. This man-madenoise often has impulsive characteristics. The statisticalmodel of impulse noise helps us a great deal for the designof reliable communication. Therefore many statistical stud-ies of impulse noise have been done not only for PLC [1–3]but for wireless communication [4,5] and digital subscriberline (DSL) [6,7].As an early work, Chan and Donaldson investigated thestatics of indoor power line impulse noise [1]. However,their investigation is restricted to the frequency range be-low 200kHz. Zimmerman and Dostert extended the knowl-edge about power line impulse noise in the frequency rangefromsomehundredkHzupto20MHz[2,3]. Theyclassiﬁedpower line noise into ﬁve category as follows:(1) colored background noise,(2) narrowband noise,(3) periodicimpulsenoiseasynchronoustothemainsfre-quency,(4) periodic impulse noise synchronous to the mains fre-quency, and(5) asynchronous impulse noise.Furthermore,theyproposedastatisticalmodelfordurationsand interarrival times of the asynchronous impulse noise.However, their analysis and modeling was for access PLC,they did not provide any statistical model for amplitudes ofthe impulse noise, and their modeling cannot be applied tohigh speed PLC as the minimum unit of impulse durationswas 80

Yoshiteru Morihiro

Papers

Turbo decoding in impulsive noise environment

A decoding for low density parity check codes over impulsive noise channels

Performance Evaluation of CMFB Transmultiplexer for Broadband Power Line Communications under Narrowband Interference

The Correlation between Radiated Emissions and Power Line Network Components on Indoor Power Line Communications

Modeling of Impulse Noise for Indoor Broadband Power Line Communications