Analysis of the probability of sync-words in Reed-Solomon codes

Abstract: Given binary data transmission encoded using a Reed-Solomon (RS) code and employing binary sync-words (markers) for synchronization, we calculate the probability of finding the sync-word in the codewords of the RS code as PS. We give analytical expressions for calculating PS, which is applicable to RS codes. Knowledge of PS can be used to calculate the probability of finding a sync-word that is used as a marker in RS encoded data, PT . The probability PT is called the false acquisition probability in the synchonization of RS encoded data

Trellis coded 4-ary PAM using distance preserving mapping

Abstract: A trellis coded 4-ary Pulse Amplitude Modulation (4-PAM) is presented, where the encoding algorithm is derived from Distance Preserving Mapping (DPM) algorithm. In this work, we modify the DPM algorithm for 4-PAM and obtain a new construction for mapping binary sequences to permutation sequences, where the permutation sequences are obtained by permuting symbols of a 4-PAM constellation. The resulting codebook of permutation sequences formed this way are termed mappings. We also present several metrics for assessing the performance of the mappings from our construction, and we show that a metric called the Sum of Product of Distances (SOPD) is the best metric to use when judging the performance of the mappings. Finally, performance results are presented, where the mappings from our construction are compared against each other and also against the conventional mappings in the literature. Index Terms—Distance-preserving mappings, Hamming distance, Euclidean distance, Pulse Amplitude Modulation

Synchronization with permutation codes and Reed-Solomon codes

D.Ing. (Electrical And Electronic Engineering)We address the issue of synchronization, using sync-words (or markers), for encoded data. We focus on data that is encoded using permutation codes or Reed-Solomon codes. For each type of code (permutation code and Reed-Solomon code) we give a synchronization procedure or algorithm such that synchronization is improved compared to when the procedure is not employed. The gure of merit for judging the performance is probability of synchronization (acquisition). The word acquisition is used to indicate that a sync-word is acquired or found in the right place in a frame. A new synchronization procedure for permutation codes is presented. This procedure is about nding sync-words that can be used speci cally with permutation codes, such that acceptable synchronization performance is possible even under channels with frequency selective fading/jamming, such as the power line communication channel. Our new procedure is tested with permutation codes known as distance-preserving mappings (DPMs). DPMs were chosen because they have de ned encoding and decoding procedures. Another new procedure for avoiding symbols in Reed-Solomon codes is presented. We call the procedure symbol avoidance. The symbol avoidance procedure is then used to improve the synchronization performance of Reed-Solomon codes, where known binary sync-words are used for synchronization. We give performance comparison results, in terms of probability of synchronization, where we compare Reed-Solomon with and without symbol avoidance applied

BPSK-OFDM versus QFSK-OFDM in combating the effects of narrowband interference and impulsive noise in power line communication

Abstract: This work serves to demonstrate the use of hybrid QFSK-OFDM and modified BPSK-OFDM in combating the effects of Narrowband Interference (NBI) and Impulsive noise (IN) as a mixture in Power Line Communication channel. Therefore, in this paper we demonstrate the superiority of modified BPSK-OFDM over QFSK-OFDM and over conventional BPSK-OFDM. The performance analysis of the system is carried out by Matlab simulations whereby the noise models used are the Middleton Class A for IN and NBI models as found in literature. The simulations show modified BPSK-OFDM to have better performance of 5 dB in terms of SNR as compared to QFSK-OFDM and 3 dB better than the conventional BPSK-OFDM

Performance comparison of Modified BPSK-OFDM and QFSK-OFDM in PLC Channel noise

The article describes and compares two OFDMbased communications schemes for reducing the effects of thecombination of Narrowband Interference (NBI) and ImpulsiveNoise (IN), which are noise types typical in Power Line Communication(PLC). The two schemes are Modified BPSK-OFDM(called MBPSK, for brevity) and QFSK-OFDM (called QFSK,for brevity), which are non-conventional OFDM schemes. Wegive a description of the two schemes, showing how they arederived and also show their similarities and eventually comparetheir performances. Performance simulation results, in termsof bit error rate, are given to compare the systems under theeffect of IN and NBI. The popular Middleton Class A modelis used for modelling IN. The results show that MBPSK schemeoutperforms the QFSK scheme in terms of minimum distance,and hence in terms of bit error probability when no preprocessingis performed. However, under clipping/nulling, both schemeseventually reach the bit error rate floor

Reed-Solomon code symbol avoidance

A Reed-Solomon code construction that avoids or excludes particular symbols in a linear Reed-Solomon code is presented. The resulting code, from our symbol avoidance construction, has the same or better error-correcting capabilities compared to the original Reed-Solomon code, but with reduced efficiency in terms of rate. The codebook of the new code is a subset of the original Reed-Solomon code and the code may no longer be linear. We also present computer search results for the bound on the number of symbols that can be avoided, and we make an attempt to find an expression for the bound. Such a code, by symbol avoidance, can be well suited to a number of applications, some of which include markers for synchronization, frequency hopping signatures, and pulse position modulation

Waveform clipping in FSK modulated signal to combat impulse noise

Abstract: This article presents results on the pre-processing (clipping/nulling) of impulse noise corrupted signal that is digitally modulated. The novelty of the article is in performing the clipping technique on the waveform of the digitally modulated signal as opposed to working with the constellation of the modulated signal. We present bit error rate performance results of Frequency Shift Keying (FSK) modulation in the presence of impulse noise and AWGN, when clipping is performed. We furthermore, develop closed-form expressions for the bit error rates of FSK modulation in the presence of both AWGN and impulse noise, when clipping of the received signal has been performed

Interleaving and nulling to combat narrow-band interference in PLC standard technologies PLC G3 and PRIME

Three functional blocks of the PRIME and PLC G3 technologies (encoder/decoder, interleaver, and modulator) are studied in detail, for a PLC channel with narrow-band interference (NBI). The study reveals that these three blocks can be used together effectively so as to improve the performance of the overall system in the presence of NBI. We therefore present effective methods for combating NBI in PRIME and PLC G3, based on these three functional blocks

Characteristics and performance of soil, bentonite and conductive cement during impulse tests in Swaziland

The essence of grounding in power systems is very essential. This paper presents the performance and characteristic of backfill material such as bentonite and conductive cement. The backfill materials pay a pivotal role in controlling ground impedance of the soil. Protective devices are normally used to divert an excessive current during lightning strikes through earth rode to avoid damages to the equipment. Swaziland has been experiencing a lot of power failures due to lightning especially during rainy season. Most of their transformers has been lost because of this problem. Most of Swaziland network is overhead which is exposed to lightning. It is thus important to design an effect earthing system that will be able to protect the equipment during fault conditions. In this study, it has been found that the behaviour of backfill material depends on the voltage applied. It was also found that the time to breakdown in comparison between bentonite and conductive cement. This paper highlights some of the aspects need to take into consideration for grounding for a country like Swaziland

Applications of artificial intelligence in powerline communications in terms of noise detection and reduction : a review

Abstract: The technology which utilizes the power line as a medium for transferring information known as powerline communication (PLC) has been in existence for over a hundred years. It is beneficial because it avoids new installation since it uses the present installation for electrical power to transmit data. However, transmission of data signals through a power line channel usually experience some challenges which include impulsive noise, frequency selectivity, high channel attenuation, low line impedance etc. The impulsive noise exhibits a power spectral density within the range of 10-15 dB higher than the background noise, which could cause a severe problem in a communication system. For better outcome of the PLC system, these noises must be detected and suppressed. This paper reviews various techniques used in detecting and mitigating the impulsive noise in PLC and suggests the application of machine learning algorithms for the detection and removal of impulsive noise in power line communication systems