Showing items 1 - 15 of 15

Your selections:

Combating impulsive noise and narrowband interference as a mixture in a power line communications channel

- Bolaji, Abiola

Synchronization with permutation codes and Reed-Solomon codes

- Shongwe, Thokozani Calvin

  • Authors: Shongwe, Thokozani Calvin
  • Date: 2014-09-23
  • Subjects: Coding theory , Synchronization , Data transmission systems , Reed-Solomon codes , Permutations
  • Type: Thesis
  • Identifier: http://ujcontent.uj.ac.za8080/10210/386508 , uj:12373 , http://hdl.handle.net/10210/12157
  • Description: 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.
  • Full Text:

Coding for the correction of synchronization errors

- Helberg, Albertus Stephanus Jacobus

  • Authors: Helberg, Albertus Stephanus Jacobus
  • Date: 2014-09-30
  • Subjects: Coding theory , Synchronization
  • Type: Thesis
  • Identifier: uj:12439 , http://hdl.handle.net/10210/12226
  • Description: Ph.D. (Electrical & Electronic Engineering) , In the ideal communication system no noise is present and error free communication is possible. In practice, however, several factors influence the correctness of· the communication. One of the most important of these factors is the synchronization of the message. Synchronization techniques form an integral part of data communication systems and without synchronization no comprehensible message can be received. An example of a communication system in which synchronization errors occur is the plesiochronous communication network which is used in many telephone networks [49,50]. A common problem with the use of the multiplexers in such a network is that output pulses may occur that do not contain valid data, due to minor discrepancies in the clock frequencies of the incoming signals. These inserted bits are termed ''justification bits" and their presence is signaled over the link by the justification control bits or stuffing control bits, which are included in the frame [49 and 50]. Synchronization of the network is dependent, among other factors, on the correct decoding of the stuffing control bits. Synchronization at the receiver can also be lost when the frame markers are not recognizable due to errors on the channel...
  • Full Text:

Concatenated permutation codes to correct substitution, deletion or transposition errors

- Heymann, Reolyn

Reed-Solomon coding for power line communications and networks

- Versfeld, Daniël Johannes Jacobus

  • Authors: Versfeld, Daniël Johannes Jacobus
  • Date: 2012-06-06
  • Subjects: Reed-Solomon codes , Electric lines , Electric networks , Coding theory
  • Type: Thesis
  • Identifier: uj:2522 , http://hdl.handle.net/10210/4978
  • Description: D.Ing. , In this study we consider the application of Reed-Solomon codes on two distinct channels. The first channel is the packet erasure channel, where packets are either received errorfree,or packets are lost. The second channel is the power line channel where additive Gaussian noise,, impulsive noise and narrowband noise are encountered In this thesis we focus on M-FSK modulation for the power line channel. For the packet erasure channel,we develop two new erasures-only decoders .The distinction between the two decoders is that the one is optimized for burst erasure correction, while the second decoder is optimized for random erasure correction.It is found that for single burst erasures, or bursterasures contained within n - k elements (where n is the code length and k is the number of information elements to be encoded), the best performance is obtained with the burst erasure decoder. When used in conjunction with a modified interleaver found in the literature, the developed random erasure decoder yields the best all-round performance. The main contribution to the power line channel is the development of a combined demodulation and decoding strategy to detect narrowband interference When standard Reed-Solomon codes operate in a channel where narrowband interference is present, undetected errors result. With the proposed decoding strategy it is found that wideband noise (a generalization of impulsive noise) affects the performance more negatively than narrowband noise for M-FSK modulation. .
  • Full Text:

Coding and bounds for correcting insertion/deletion errors

- Swart, Theo G.

  • Authors: Swart, Theo G.
  • Date: 2012-09-10
  • Subjects: Error-correcting codes (Information theory) , Coding theory
  • Type: Thesis
  • Identifier: uj:9925 , http://hdl.handle.net/10210/7324
  • Description: M.Ing. , Certain properties of codewords after deletions or insertions of bits are investigated. This is used in the enumeration of the number of subwords or superwords after deletions or insertions. Also, new upper bounds for insertion/deletion correcting codes are derived from these properties. A decoding algorithm to correct up to two deletions per word for Helberg's s = 2 codes is proposed. By using subword and superword tables, new s = 2 codebooks with greater cardinalities than before are presented. An insertion/deletion channel model is presented which can be used in evaluating insertion/deletion correcting codes. By changing the parameters, various channel configurations can be attained. Furthermore, a new convolutional coding scheme for correcting insertion/deletion errors is introduced and an investigation of the performance is done by using the presented channel model.
  • Full Text:

Performance ranking and implementation of permutation coded orthogonal frequency division multiplexing for power-line communications

- Ogunyanda, Kehinde

Viterbi decoding of ternary line codes

- Ouahada, Khmaies

Design of balanced q-ary interleaved sequences

- Musarurwa, Dadiso Florence

Pruned convolutional codes and Viterbi decoding with the Levenshtein distance metric

- Cheng, Ling

  • Authors: Cheng, Ling
  • Date: 2009-02-26T12:16:46Z
  • Subjects: Error-correcting codes (Information theory) , Coding theory , Convolutions (Mathematics)
  • Type: Thesis
  • Identifier: uj:8147 , http://hdl.handle.net/10210/2154
  • Description: M.Ing. , In practical transmission or storage systems, the convolutional encoding and Viterbi decoding scheme is widely used to protect the data from substitution errors. Two independent insertion/deletion/substitution (IDS) error correcting designs, working on the convolutional encoder and the Viterbi decoder respectively, are shown in this thesis. The Levenshtein distance has previously been postulated to be a suitable branch comparison metric for the Viterbi algorithm on channels with not only substitution errors, but also insertion/deletion errors. However, to a large extent, this hypothesis has still to be investigated. In the first coding scheme, a modified Viterbi algorithm based on the Levenshtein distance metric is used as the decoding algorithm. Our experiments give evidence that the modified Viterbi algorithm with the Levenshtein distance metric is suitable as an applicable decoding algorithm for IDS channels. In the second coding scheme, a new type of convolutional code called the path-pruned convolutional code is introduced on the encoder side. By periodically deleting branches in a high rate convolutional code trellis diagram to create a specific insertion/deletion error correcting block codeword structure in the encoded sequence, we can obtain an encoding system to protect against insertion, deletion and substitution errors at the same time. Moreover, the path-pruned convolutional code is an ideal code to use for unequal error protection. Therefore, we also present an application of the rate-compatible path-pruned convolutional codes over IDS channels.
  • Full Text:

Multiple insertion/deletion correcting and detecting codes : structural analysis, constructions and applications

- Paluncic, Filip

  • Authors: Paluncic, Filip
  • Date: 2012-08-01
  • Subjects: Error-correcting codes (Information theory) , Coding theory , Engineering mathematics
  • Type: Thesis
  • Identifier: uj:8894 , http://hdl.handle.net/10210/5366
  • Description: D.Ing. , This thesis is dedicated to an analysis of fundamental topics and issues related to deterministic insertion/deletion correcting and detecting codes. The most important contributions in this respect are the construction of a multiple insertion/deletion correcting code for run-length limited sequences and the construction and applications of multiple deletion (insertion) detecting codes. It is shown how run-length constraints and higher order moments can be combined to create a code which is simultaneously multiple insertion/deletion error correcting and runlength constrained. A systematic form of this code is presented, whereby any arbitrary run-length constrained sequence can be made into a multiple insertion/deletion correcting codeword by adding a prefix. This prefix is appended to the run-length constrained sequence in such a way that the resulting codeword is itself run-length constrained. Furthermore, it is shown that, despite the run-length constraints, the resulting code is guaranteed to have a better asymptotic rate than the Helberg code, the only other known non-trivial deterministic multiple insertion/deletion correcting code. We consider insertion/deletion detecting codes and present a multiple deletion (insertion) detecting code. It is shown that this code, which is systematic, is optimal in the sense that there exists no other systematic multiple deletion (insertion) detecting code with a better rate. Furthermore, we present a number of applications of such codes. In addition, further related topics of interest are considered. Firstly, jitter as a fundamental cause of insertion/deletion errors is investigated and as a result a counterpart to the signal-to-noise ratio in the amplitude domain is proposed for the time domain. Secondly, motivated by the correspondence of Levenshtein and Varshamov-Tenengol’ts codes, we investigate the insertion/deletion correcting capability of the single asymmetric error correcting Constantin-Rao codes within a wider framework of asymmetric error correcting and insertion/deletion correcting code structure correspondences. Finally, we propose a generalisation of Tenengol’ts’ construction for multiple non-binary insertion/deletion correction.
  • Full Text:

Constrained Codes capable of correcting insertion/deletion burst errors by using markers

- Smith, Dylan

Low disparity channel coding schemes for DC free transmission

- Heymann, Carl

  • Authors: Heymann, Carl
  • Date: 2018
  • Subjects: Coding theory , Markov processes , Information theory , Electric current converters
  • Language: English
  • Type: Masters (Thesis)
  • Identifier: http://hdl.handle.net/10210/262895 , uj:27787
  • Description: Abstract: In this dissertation, three new DC free coding schemes are presented. The first is inspired by the balancing scheme by Knuth, as well as the work by Frontana, Jamieson and Fair. It is a multi-mode, low-disparity scheme, that controls the running digital sum (RDS) of a sequence by creating an inversion point, indicated by a number of redundant prefix bits. The number of prefix bits can be varied in the design of a specific scheme, allowing the designer to trade code rate for DC suppression performance. The second scheme uses the same concepts, applied to run-length limited (RLL) sequences. The new scheme inserts a fixed-length, inverting marker at a point in each codeword such that the overall sequence’s RDS is minimised. The third coding scheme is a variable-length scheme applied to run-length limited sequences. It inserts special marker runs, of a reserved run-length, whenever the RDS exceeds a threshold value. A Markov chain model is presented, allowing the code rate and RDS variance to be accurately predicted when encoding maxentropic RLL sequences. A lower RDS variance reflects better DC-suppression performance. , M.Ing. (Electrical Engineering)
  • Full Text:

Insertion/deletion correction by using parallel-interconnected viterbi decoders

- Swart, Theo G., Ferreira, Hendrik C., Dos Santos, M. P. F.

Performance evaluation of some (d,k) codes

- Coetzee, Chris Stefan

  • Authors: Coetzee, Chris Stefan
  • Date: 2014-09-30
  • Subjects: Coding theory , Modulation (Electronics
  • Type: Thesis
  • Identifier: uj:12431 , http://hdl.handle.net/10210/12219
  • Description: M.Ing. (Electrical & Electronic Engineering) , Coding is indispensable in modem communications and storage systems. For instance, a Reed-Solomon error-correction code ensures higher data integrity for the Compact Disc (CD) system. Modulation codes, such as the( d, k) codes, can furthermore be employed to enable synchronization between transmitter and receiver (or between the read and write processes in storage systems), and also to achieve compliance with bandwidth restrictions. In some cases, a 'combined' code is designed to function both as an error control code and a (d, k) modulation code. In this study, we consider such an existing class of error control (d, k) block codes. Of particular interest is the performance of these codes, determined mostly in terms of the probability of block error over certain selected channels. It is important to be able to judge or predict the performance of a communication system in terms of the probability of receiving incorrect information, and this probability depends not only on the specific error control code used, but also on the statistical structure of the channel error processes. The main contributions of this thesis are seen to be the following: 1) New codes and improvements on previous codes, originating from the generalization of existing theory. 2) Mathematical bounds and approximations on block error rates, compared with measured results from computer simulations.
  • Full Text:
  • 1
  • Disclaimer
  • Privacy
  • Copyright
  • Contact