A. D. Familua

Constant envelope OFDM transmission over impulsive noise power-line communication channels

Signal blanking is a simple and efficient method to reduce the effect of impulsive noise over power-line channels. The efficiency of this method, however, is found to be not only impacted by the threshold selection but also by the average peak-to-average ratio (PAPR) value of the orthogonal frequency division multiplexing (OFDM) signals. As such, the blanking capability can be further enhanced by reducing the PAPR value. With this in mind, in this paper we evaluate the performance of constant envelope OFDM (CE-OFDM) which has inherently the lowest achievable PAPR of 0 dB; therefore, the proposed system is expected to provide the lower bound performance of the blanking-based method. In order to characterize system performance, we consider the probability of blanking error and signal-to-noise ratio (SNR) at the output of the blanking device. The results reveal that the proposed system can achieve significant improvements over the conventional OFDM blanking-based scheme in terms of minimized probability of blanking error. It will also be shown that output SNR gains of up to 6 dB can be attained over the conventional OFDM blanking-based systems.

Narrowband PLC channel modeling using USRP and PSK modulations

The indoor narrowband power line communication (NB-PLC) suffers from noise impairments, which emanate from several end-user electrical devices connected across the PLC channel. These noise impairments result into burst errors, which consequently lead to data corruption. Therefore, in order to implement robust communication techniques that will thrive on the noisy PLC channel, a full knowledge and modeling of the noise that exists on the NB-PLC channel is inevitable. This paper thus reports a First-order Markov modeling of NB-PLC channel noise, based on experimental measurements. For the modeling, BPSK, DBPSK, QPSK and DQPSK modulation schemes were implemented using Universal Software Radio Peripheral (USRP). The resulting channel models are useful for improving the robustness of the above modulation schemes as well as designing forward error correction techniques for mitigating the effect of noise impairments. The results are also useful in optimizing NB-PLC system design, thereby, enhancing the accuracy and improving the overall PLC system performance.

A Semi-hidden Markov modeling of a low complexity FSK-OOK in-house PLC and VLC integration

The integration of power line communication (PLC) and visible light communication (VLC) is increasingly receiving a lot of research interest with the advent of (IEEE 1901, ITUT G.9960/61) and IEEE 802.15.7 standards for PLC and VLC respectively. In particular, there is an underlying gain that could be achieved by leveraging the existing ubiquitous power line network infrastructure to render connectivity, while we also exploit the illumination system of power-saving Light Emitting Diodes (LEDs) for wireless data communication. The ubiquitous nature of these two systems makes us belief that VLC can offer a good complementary wireless data transmission technology to the existing In-House PLC in a similar manner broad-band Ethernet connections enjoys the support of Wi-Fi. This paper thus reports an implementation of a low complexity FSK-OOK In-House PLC and VLC Integration, as well as its Second-Order Semi-Markov Model. The resulting statistical models facilitates the design and evaluation of forward error correcting codes to mitigate burst error occurrences, as well as optimizing the performance of the overall system.

Error pattern/behavior of noise in in-house CENELEC A-Band PLC channel

The CENELEC A-Band remains the most noise-susceptible band amidst the four standard CENELEC Power Line Communication (PLC) frequency bands. The characteristics of this noise change with time, place, source and frequency. This paper presents experimental simulations as well as results obtained during laboratory experiments and in-house measurements within the CENELEC A narrowband PLC channel. These measurements were carried out between 3 kHz and 95 kHz, as defined by the CENELEC standard as frequency band A. The A Band is the frequency band where communication is carried out by electricity providers, and various factors make it noise prone as mentioned above. Repetitive measurements of noise patterns were carried out in two different typical metropolitan locations in South Africa and were observed in hourly intervals for 24 hours with various different noise generating sources. The obtained A-Band noise pattern has distinctive frequencies and their amplitudes can be quantified. The noise pattern/behavior is classified into background noise, narrow band interference and impulse noise, and could be mathematically modeled. Having measured the noise and understanding the noise pattern/behavior, the use of an appropriate error coding scheme and adaptive modulation scheme are proposed to mitigate the effect of these disturbances in order to enhance reliable data communication on this band.

Adaptive permutation coded differential OFDM system for power line communications

With a view to improving the capacity of the differential OFDM modulation scheme, specified in the narrowband power line communications (PLC) standards, in combating PLC channel associated noise, we hereby propose a permutation coded modulation scheme, which employs the hybridization of two kinds of DPSK (differential phase shift keying) modulations in an adaptive manner. The algorithm for deducing the encoded information from the hybridized modulations is described as well. This scheme is simulated and its performance is compared with a recently reported differential quinary PSK-OFDM system in the literature, whose behaviour has been shown to be better than the conventional permutation coded D8PSK-OFDM scheme at lower signal power to noise spectral density. Due to the simplicity in its encoding and decoding algorithms, this scheme is a good candidate for a number of low speed telemetry signaling in smart grids.

Evaluation and implementation of cyclic permutation coding for power line communications

Noise and attenuation, in the form of frequency disturbance, impulsive noise, additive white Gaussian noise (AWGN) and frequency selective fading, are the major setbacks in power line communications (PLC). In order to effectively combat this challenge, we thus report the development and implementation of a specially coded M-ary differential phase shift keying modulation scheme on narrowband PLC channel. The coding aspect involves the concatenation of conventional Reed Solomon (RS) code with cyclic permutation coding (CPC), resulting in what is termed RS-CPC scheme. The CPC employed in this work maps the output bits of a binary RS code onto non-binary CPC symbols, in a cyclic manner, with a view to improving the distance between two different sets of mapped symbols. For implementation over 230 V AC power line, software defined radio hardware, called the universal software radio peripherals (USRPs), were used, together with narrowband coupling circuits, to couple the signal to and receive it from the power line. Both by simulation and implementation, our scheme outperforms the conventional Reed Solomon-convolutional coding (RS-CC) specified in the G3-PLC standard. An added advantage is that our scheme is easier to implement.

Modeling of in-house CENELEC A-band PLC channel using Fritchman model and Baum-Welch algorithm

One of the many challenges which power line communication (PLC) has to overcome is noise and disturbances. Amidst the four frequency bands classified by the European CENELEC standard, the A-band is the most noise susceptible characterized by noise sources consisting of various electrical appliances. This paper aims at modeling the noise and disturbances present on the in-house CENELEC A-band based on experimental measurement. The outputs are the channel models of the three major types of noise present on the PLC. These models are achieved through the use of Fritchman model, to depict the power line channel and evaluate the noise impairment caused by the different types of noise. The Baum-Welch algorithm is implemented for the Fritchman model parameter estimation through likelihood evaluation by computing the probabilities of three different noise observation sequences obtained from the experimental measurement. These channel models can then be used to evaluate and optimize coding and modulation schemes for PLC.

First and Second-Order Semi-Hidden Fritchman Markov models for a multi-carrier based indoor narrowband power line communication system

Abstract The realization of a Semi-Hidden Fritchman Markov models (SHFMMs) for power line communication (PLC) channel is only practicable if combined with efficient algorithms for learning and inference.xa0This article thus reports First and Second-Order SHFMMs for the bit error pattern at the output of an Orthogonal Frequency Division Multiplexing based system for in-home narrowband PLC applications.xa0Accurate SHFMMs have been derived for a residential and laboratory environment using the efficient iterative Baum–Welch algorithm.xa0The log-likelihood ratio plots, the error-free run distribution plots, the mean square error and Chi-Square ( χ 2 ) test validates the accuracy of the derived models.xa0The reliability and accuracy of resulting models are confirmed by a close match between the measured bit error sequences and the model generated bit error sequences.xa0The estimated Second-Order SHFMMs have been validated to be superior to the First-Order models, although at the expense of more computational complexity.xa0Resulting models assist designers to speed up and facilitate the process of designing and evaluating novelties for PLC systems.

Evaluation of mixed permutation codes in PLC channels, using Hamming distance profile

We report a new concept involving an adaptive mixture of different sets of permutation codes (PC) in a single DPSK–OFDM modulation scheme. Since this scheme is robust and the algorithms involved are simple, it is a good candidate for implementation for OFDM-based power line communication (PLC) systems. By using a special and easy concept called Hamming distance profile, as a comparison tool, we are able to showcase the strength of the new PC scheme over other schemes reported in literature, in handling the incessant noise types associated with PLC channels. This prediction tool is also useful for selecting an efficient PC codebook out of a number of similar ones.