Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: In recent years South African wines have been under the spotlight due to references in the international wine media to a distinctive ‘burnt rubber’ character. Many winemakers and wine experts argued that the peculiar character could be ascribed to winemaking errors linked to mismanaged fermentation. An alternative possible source of the taint was identified in the coal tar creosote used as a wood preservative in vineyard trellis systems. South African regulations allow for the use of creosoted utility poles in agricultural land, but in Europe and USA their usage has been highly regulated and even banned for certain applications. Contamination of foodstuff by polycyclic aromatic hydrocarbons (PAHs) is one of the major motives for the banning of creosote in Europe and USA. Some of the compounds in the creosote mixture display very strong odour characteristics and for this reason it became the focus of attention for the present study. The overall aim of this study was to determine if vines trellised with creosoted posts could accumulate or absorb the various malodorous compounds deriving from the wood treatment onto the grape berries. These compounds could then be extracted from the grape berries into the wine during alcoholic fermentation, creating quality and sensory problems. Chapter 2 of this thesis gives an overview of the extensive literature that deals with methods of analysis of PAHs and malodorous phenols using both Gas Chromatography (GC), as well as High Performance Liquid Chromatography (HPLC). New methods for sample preparation, as well as analysis of PAHs using HPLC-Diode Array Detector (DAD), were developed and the results reported in Chapter 3. It was demonstrated that Sauvignon blanc experimental wines contained only chrysene at very low levels. The concentrations of chrysene found in the experimental wines are within the prescribed parameters as established by The Commission of the European Communities. Since no other PAH compounds were found in the samples analysed, it was concluded that the experimental wines were safe for human consumption and complied with EU regulations. The effect of vineyard posts on the sensorial characteristics of wine is discussed in Chapter 4. Creosoted poles were found to be responsible for an off-flavour described as ‘burnt rubber’ and ‘tarry’ in Merlot wines produced from grapes grown in close proximity to the posts. Following some of the reported findings, new guidelines have been introduced in the Integrated Production of Wine certification, which advise against the use of creosoted poles for vineyard trellising. This preliminary but important guideline will bring the South African wine industry a step closer to the fulfilling the obligations for food safety as required by the legislation of our major export partners. Future investigations are recommended to completely understand and evaluate the cumulative effect of creosoted posts in a fully trellised vineyard. / AFRIKAANSE OPSOMMING: Oor die afgelope paar jaar is Suid-Afrikaanse wyne onder die soeklig geplaas as gevolg van verwysings in die internasionale wynmedia na ‘n duidelike ‘gebrande rubber’-karakter. Baie wynmakers en wyndeskundiges het aangedui dat hierdie besonderse karakter toegeskryf kan word aan wynbereidingsfoute wat verband hou met gisting wat wanbestuur is. ‘n Alternatiewe moontlike oorsprong van die smaak is geïdentifiseer in die koolteer wat as ‘n houtpreserveermiddel in wingerdopleistelsels gebruik word. Suid-Afrikaanse regulasies maak voorsiening vir die gebruik van kreosoteerde nutspale in landbougrond, hoewel hulle gebruik in Europa en die VSA hoogs gereguleerd en in sommige gevalle selfs verbied is. Die besmetting van kossoorte deur polisikliese aromatiese koolwaterstowwe (polycyclic aromatic hydrocarbons (PAHs)) is een van die vernaamste redes vir die verbanning van kreosoot in Europa en die VSA. Sommige van die verbindings in die kreosootmengsel het baie sterk geurkenmerke en daarom is dit die fokus van die huidige studie. Die oorhoofse doelwit van hierdie studie was om te bepaal of wingerde wat op kreosoteerde pale opgelei is, die verskillende onwelriekende verbindings afkomstig van die houtbehandeling in die druiwekorrels kan akkumuleer of absorbeer. Hierdie verbindings sou dan tydens alkoholiese gisting uit die druiwekorrels in die wyn geëkstraheer kon word, wat aanleiding sou gee tot kwaliteits- en sensoriese probleme. Hoofstuk 2 van hierdie tesis verskaf ‘n oorsig van die breedvoerige literatuur wat handel oor metodes om PAH’s en onwelriekende fenole met behulp van beide gaschromatografie (GC) en hoëdrukvloeistofchromatografie (HPLC) te analiseer. Nuwe metodes is ontwikkel om monsters voor te berei en om PAH’s met behulp van ‘n HPLC-diode array detector (DAD) te analiseer. Die resultate word in Hoofstuk 3 gerapporteer. Daar is aangetoon dat die eksperimentele Sauvignon blanc-wyne chriseen teen baie lae vlakke bevat het. Die konsentrasies van chriseen wat in die eksperimentele wyne gevind is, is binne die voorgeskrewe parameters van die Kommissie van die Europese Gemeenskap. Aangesien daar nie ander PAHverbindings in die geanaliseerde monsters gevind kon word nie, is daar tot die gevolgtrekking gekom dat die eksperimentele wyne veilig is vir menslike verbruik en aan die EG-regulasies voldoen. Die effek van wingerdpale op die sensoriese kenmerke van wyn word in Hoofstuk 4 bespreek. Kreosoteerde pale is gevind wat verantwoordelik is vir ‘n wangeur in Merlot-wyne afkomstig van druiwe wat naby die pale gegroei het en wat as ‘gebrande rubber’ en ‘teeragtig’ beskryf is. Op grond van sommige van die gerapporteerde bevindings, is nuwe riglyne ingesluit in die sertifisering vir die Geïntegreerde Produksie van Wyn, wat aanbeveel dat kreosoteerde pale nie vir wingerdoplei gebruik word nie. Hierdie voorlopige, maar belangrike riglyn sal die Suid-Afrikaanse wynbedryf al beter in staat stel om te voldoen aan die voedselveiligheid regulasies wat vereis word deur die wetgewing van ons belangrikste uitvoervennote. Toekomstige ondersoeke moet aangewend word om die kumulatiewe effek van kreosoteerde pale in volledig opgeleide wingerde ten volle te verstaan en te evalueer. / Indaba Scholarship and Winetech for their financial support

Channel coding has been largely used for the purpose of improving error performance on a communications system. Typical methods based on added redundancy allow for error detection and correction, this improvement however comes at a cost of bandwidth. This thesis focuses on channel coding for the bandwidth-limited channel where no bandwidth expansion is allowed. We first discuss the idea of coding for the bandwidth-limited channel as seen from the signal space point of view where the purpose of coding is to maximize the Euclidian distance between constellation points without increasing the total signal power and under the condition that no extra bits can be added. We then see the problem from another angle and identify the tradeoffs related to bandwidth and error performance. This thesis intends to find a simple way of achieving an improvement in error performance for the bandwidth-limited channel without the use of lattice codes or trellis-coded modulation. The proposed system is based on convolutional coding followed by multilevel transmission. It achieved a coding gain of 2 dB on Eb/No or equivalently, a coding gain of approximately 2.7 dB on SNRnorm without increase in bandwidth. This coding gain is better than that obtained by a more sophisticated lattice code Gosset E8 at the same error rate.

As the demand of high data rate is increasing, a lot of research is being conducted in the field of wireless communication. A well-known channel coding technique called Space-Time Coding has been implemented in the wireless Communication systems using multiple antennas to ensure the high speed communication as well as reliability by exploiting limited spectrum and maintaining the power. In this thesis, Space-Time Coding is discussed along with other related topics with special focus on Alamouti Space-Time Block Code. The Alamouti Codes show good performance in terms of bit error rate over Rayleigh fading channel. The performance of Altamonte’s code and MIMO capacity is evaluated by using MATLAB simulation.

The area of cooperative communications has received tremendous research interest in recent years. This interest is not unwarranted, since cooperative communications promises the ever-so-sought after diversity and multiplexing gains typically associated with multiple-input multiple-output (MIMO) communications, without actually employing multiple antennas. In this dissertation, we consider several cooperative communication channels, and for each one of them, we develop information theoretic coding schemes and derive their corresponding performance limits. We next develop and design practical coding strategies which perform very close to the information theoretic limits. The cooperative communication channels we consider are: (a) The Gaussian relay channel, (b) the quasi-static fading relay channel, (c) cooperative multiple-access channel (MAC), and (d) the cognitive radio channel (CRC). For the Gaussian relay channel, we propose a compress-forward (CF) coding strategy based on Wyner-Ziv coding, and derive the achievable rates specifically with BPSK modulation. The CF strategy is implemented with low-density parity-check (LDPC) and irregular repeataccumulate codes and is found to operate within 0.34 dB of the theoretical limit. For the quasi-static fading relay channel, we assume that no channel state information (CSI) is available at the transmitters and propose a rateless coded protocol which uses rateless coded versions of the CF and the decode-forward (DF) strategy. We implement the protocol with carefully designed Raptor codes and show that the implementation suffers a loss of less than 10 percent from the information theoretical limit. For the MAC, we assume quasi-static fading, and consider cooperation in the low-power regime with the assumption that no CSI is available at the transmitters. We develop cooperation methods based on multiplexed coding in conjunction with rateless codes and find the achievable rates and in particular the minimum energy per bit to achieve a certain outage probability. We then develop practical coding methods using Raptor codes, which performs within 1.1 dB of the performance limit. Finally, we consider a CRC and develop a practical multi-level dirty-paper coding strategy using LDPC codes for channel coding and trellis-coded quantization for source coding. The designed scheme is found to operate within 0.78 dB of the theoretical limit. By developing practical coding strategies for several cooperative communication channels which exhibit performance close to the information theoretic limits, we show that cooperative communications not only provide great benefits in theory, but can possibly promise the same benefits when put into practice. Thus, our work can be considered a useful and necessary step towards the commercial realization of cooperative communications.

In this thesis, we present low latency general concatenated code structures suitable for parallel processing. We propose parallel decodable serially concatenated codes (PDSCCs) which is a general structure to construct many variants of serially concatenated codes. Using this most general structure we derive parallel decodable serially concatenated convolutional codes (PDSCCCs). Convolutional product codes which are instances of PDSCCCs are studied in detail. PDSCCCs have much less decoding latency and show almost the same performance compared to classical serially concatenated convolutional codes. Using the same idea, we propose parallel decodable turbo codes (PDTCs) which represent a general structure to construct parallel concatenated codes. PDTCs have much less latency compared to classical turbo codes and they both achieve similar performance. We extend the approach proposed for the construction of parallel decodable concatenated codes to trellis coded modulation, turbo channel equalization, and space time trellis codes and show that low latency systems can be constructed using the same idea. Parallel decoding operation introduces new problems in implementation. One such problem is memory collision which occurs when multiple decoder units attempt accessing the same memory device. We propose novel interleaver structures which prevent the memory collision problem while achieving performance close to other interleavers.

The phenomenon of fading constitutes a fundamental problem in wireless communications. Researchers have proposed many methods to improve the reliability of communication over wireless channels in the presence of fading. Many studies on this topic have focused on diversity techniques. Transmit diversity is a common diversity type in which multiple antennas are employed at the transmitter. Space-time coding is a technique based on transmit diversity introduced by Tarokh et alii in 1998. In this thesis, various types of space-time codes are examined. Since they were originally introduced in the form of trellis codes, a major part is devoted to space-time trellis codes where the fundamental design criteria are established. Then, space-time block coding, which presents a different approach, is introduced and orthogonal spacetime block codes are analyzed in some detail. Lastly, rank codes from coding theory are studied and their relation to space-time coding are investigated.

Two standard graph representations for linear codes are the Tanner graph and the tailbiting trellis. Such graph representations allow the decoding problem for a code to be phrased as a computational problem on the corresponding graph and yield graph theoretic criteria for good codes. When a Tanner graph for a code is used for communication across a binary erasure channel (BEC) and decoding is performed using the standard iterative decoding algorithm, the maximum number of correctable erasures is determined by the stopping distance of the Tanner graph. Hence the computational problem of determining the stopping distance of a Tanner graph is of interest. In this thesis it is shown that computing stopping distance of a Tanner graph is NP hard. It is also shown that there can be no (1 + є ) approximation algorithm for the problem for any є > 0 unless P = NP and that approximation ratio of 2(log n)1- є for any є > 0 is impossible unless NPCDTIME(npoly(log n)). One way to construct Tanner graphs of large stopping distance is to ensure that the graph has large girth. It is known that stopping distance increases exponentially with the girth of the Tanner graph. A new elementary combinatorial construction algorithm for an almost regular LDPC code family with provable Ώ(log n) girth and O(n2) construction complexity is presented. The bound on the girth is close within a factor of two to the best known upper bound on girth. The problem of linear time exact maximum likelihood decoding of tailbiting trellis has remained open for several years. An O(n) complexity approximate maximum likelihood decoding algorithm for tail-biting trellises is presented and analyzed. Experiments indicate that the algorithm performs close to the ideal maximum likelihood decoder.

Στα πλαίσια της διπλωματικής εργασίας μελετήθηκε μια κατηγορία αλγορίθμων διόρθωσης λαθών που προκύπτουν κατά τη μετάδοση δεδομένων μέσα από ένα ασύρματο τηλεπικοινωνιακό κανάλι. Η μετάδοση των δεδομένων έγινε χρησιμοποιώντας τις διαμορφώσεις BPSK, QPSK, 16 – QAM και 64 – QAM. Η μελέτη επικεντρώθηκε στην περίπτωση της συνελικτικής κωδικοποίησης δεδομένων. Για την υλοποίηση του αποκωδικοποιητή (decoder) μελετήθηκαν συγκριτικά οι αλγόριθμοι Viterbi και SOVA καθώς και οι αντίστοιχες αρχιτεκτονικές υλοποίησης τους σε υλικό, ως προς την πολυπλοκότητα, την κατανάλωση και την ταχύτητά τους για συγκεκριμένη ικανότητα διόρθωσης λαθών που μετράται ως μείωση του BER. Επίσης, μελετήθηκαν τέσσερεις διαφορετικοί τρόποι αποδιαμόρφωσης και αποκωδικοποίησης των δεδομένων για διαμορφώσεις QAM βασισμένοι στον αλγόριθμο Viterbi. Η μεθοδολογία της διπλωματικής περιέλαβε την υλοποίηση ενός πλήρους μοντέλου τηλεπικοινωνιακού συστήματος με μη ιδανικό κανάλι, AWGN, στο οποίο προστέθηκαν μηχανισμοί διόρθωσης λάθους. Η μελέτη έλαβε υπόψη τον κβαντισμό στο δέκτη στην αναπαράσταση δεδομένων καθώς και στα ενδιάμεσα αποτελέσματα. Αξιολογήθηκαν τρόποι κβαντισμού συναρτήσει παραμέτρων του καναλιού, και εντοπίστηκαν τα ελάχιστα αναγκαία μήκη λέξης για την υλοποίηση των αλγορίθμων του δέκτη, λαμβάνοντας υπόψη το trade-off μεταξύ απόδοσης και κόστους υλοποίησης σε υλικό. Με τη χρήση bit-true εξομοιώσεων μελετήθηκαν τρόποι ελαχιστοποίησης της δυναμικής περιοχής που απαιτείται για την αναπαράσταση των ενδιάμεσων μετρικών. Σε κάθε περίπτωση αναλύθηκε η απόδοση των αλγορίθμων με βάση το ποσοστό των λαθών στο δέκτη (BER) ενώ συνεκτιμήθηκε η πολυπλοκότητα της αντίστοιχης υλοποίησης VLSI. / This thesis focuses on a class of algorithms for the correction of errors due of the transmission of data through a wireless telecommunications channel. The modulations employed are BPSK, QPSK, 16-QAM and 64-QAM. The study focuses on convolutional coding. The performance of solutions based on Viterbi and SOVA algorithms are comparatively studied, as well as the corresponding hardware architectures, in terms of the complexity, consumption and speed, while specifications are set in terms of error correction capability, measured in BER. Also, four different ways of combined demodulation and decoding of QAM data are studied based on the Viterbi algorithm. The methodology assumed in this thesis includes the realization of a complete telecommunications system model assuming an additive white gaussian noise channel, AWGN, in which mechanisms of error correction are added. The study takes into consideration the quantization effects in the receiver and in all the intermediary operations of algorithms. It has been found that the ideal quantizer for the receiver is related to channel parameters. In addition the shortest necessary word lengths were identified taking into consideration trade off between output and hardware realization cost. By means of bit-true simulations, ways of minimization of dynamic region, required for the representation intermediary metrics were studied. In every case the performance of algorithms is analyzed in terms of BER, as well as computational cost and impact on VLSI realization.

Orientadores: Walter da Cunha Borelli, Emilia de Mendonça Rosa Marques / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-13T08:38:40Z (GMT). No. of bitstreams: 1 SilvaFilho_JoaoCoelho_D.pdf: 842540 bytes, checksum: 07a4f12e39ce13ce6c183f2983fbe70f (MD5) Previous issue date: 2008 / Resumo: Esta tese apresenta contribuições aos esquemas de modulação codificada para os códigos de treliça sobre partições de reticulados. Uma das principais contribuições é a construção dos códigos de treliça sobre novas partições de reticulados e também em cadeias de partições. Para otimizar a procura dos códigos de treliça ótimos, é construído um algoritmo de procura. É proposta uma classe de equivalência utilizada para excluir as matrizes geradoras de códigos equivalentes, sendo que esta classe de equivalência quando aplicada ao algoritmo de procura dos códigos de treliça ótimos diminui a quantidade de matrizes geradoras a ser investigada. Apresentam-se, vários exemplos de códigos de treliça sobre reticulados quociente nos espaços bi-dimensional, tridimensional e tetra-dimensional com satisfatórios ganhos de codificação e menor energia média das constelações de sinais. / Abstract: This thesis presents some contributions to the coded modulation schemes for the trellis codes based on lattices partitioning. One of the main contributions is the construction of the trellis codes based on novel lattices partitioning and also on chains partitioning. In order to optimize the search for the optimum trellis codes, a search algorithm was proposed. An equivalence class is proposed to exclude the generator matrix of equivalent codes. This equivalence class, when applied to the search algorithm for optimum trellis codes, reduces quite strongly the number of generator matrices to be investigated. Several examples of trellis codes on lattices quotient are shown in bi-dimensional, three-dimensional and tetra-dimensional spaces with satisfactory coding gain and lower average energy of the signal constellations. / Doutorado / Telecomunicações e Telemática / Doutor em Engenharia Elétrica

Approved for public release; distribution is unlimited. / Trellis-Coded Modulation (TCM) is employed with quadrature amplitude modulation (QAM) to provide error correction coding with no expense in bandwidth. There are two common implementations of TCM, namely pragmatic TCM and Ungerboeck TCM. Both schemes employ Viterbi algorithms for decoding but have different code construction. This thesis investigates and compares the performance of pragmatic TCM and Ungerboeck TCM by implementing the Viterbi decoding algorithm for both schemes with 16-QAM and 64-QAM. Both pragmatic and Ungerboeck TCM with six memory elements are considered. Simulations were carried out for both pragmatic and Ungerboeck TCM to evaluate their respective performance. The simulations were done using Matlab software, and an additive white Gaussian noise channel was assumed. The objective was to ascertain that pragmatic TCM, with its reduced-complexity decoding, is more suitable to adaptive modulation than Ungerboeck TCM. / Civilian