Dissertations / Theses on the topic 'Design codes'

Includes bibliographical references.
This thesis confines itself to a consideration of urban development opportunity in the East City Precinct through the understanding of it former historical character and memory which can be implemented through Form Based Codes. It locates the design process in the sub-regional context and puts forward notional spatial proposal for the physical area of the East City Precinct and its surrounds. The application of theory is tested at precinct level and emphasis remains firmly on the public elements ordering the spatial structure. With all these considerations, this dissertation presents a piece of history of District Six and the importance of memory in relation to the East City. This contested site of memory and heritage informs the area’s contextual development amid the often-essentialising multicultural in particular to the ‘new South Africa’. In turn, an understanding of District Six’s urban quality which frames the intricacies of a restitution and redevelopment plan. It also illustrates the genuine uniqueness of its principles of urbanism, in contrast to market-oriented urban development which reproduces spaces of social fragmentation, exclusion and inequality. Indeed, the vision for the East City concerns long-term urban sustainability, an investment in a city of fluid spaces, a city of difference and meaning. This dissertation contends that there is a real role for urban and social sustainability in the redevelopment potential of the study area, with its historical, social, cultural and symbolic significance. Therefore its outline the key elements and principles for a development framework prepared for the study area and discuss the prospects for urban and social sustainability. This will inform where and how to apply form based codes with in the East City context.

The thesis examines Engineering Design and its methodology in general before examining and comparing the principal differences between Inventive Design and Development Design.  This latter branch of design is described in detail, recognising that it is executed in accordance with recognised specifications, design codes and standards.  Design Codes and Standards are analysed in terms of the service they provide to the professional design engineer who will normally work under the procedures and accepted standards of a Professional Design House.  Professional design is an important part of all disciplines in the engineering profession.  Such design work is executed by specialists, invariably guided in their work by recognised Specifications, Design Standards or Codes of Practice published by recognised reputable bodies who appoint working parties or independent committees to write and maintain these documents. Design Standards and Codes of Practice are at best unclear and at worst confusing if not down right contradictory within themselves. Usually there is more than one such Standard or Code available to the professional design engineer often based on geographical location; BSI in the UK, DIN or ISO in Europe and perhaps ASME ANSI in the USA. There are of course several others. The professional design process is analysed and described in order to demonstrate the commercial and project constraints associated with professional development design.  The model usually adopted in the preparation and presentation of these codes and standards is critiqued and a better model proposed for standard adoption.

ITC/USA 2005 Conference Proceedings / The Forty-First Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2005 / Riviera Hotel & Convention Center, Las Vegas, Nevada
Multiple-input multiple output (MIMO) communication systems can have dramatically higher throughput than single-input, single-output systems. Unfortunately, it can be difficult to find the space-time codes these systems need to achieve their potential. Previously published results located good codes by minimizing the maximum correlation between transmitted signals. This paper shows how this min-max method may produce sub-optimal codes. A new method which sorts codes based on the union bound of pairwise error probabilities is presented. This new technique can identify superior MIMO codes, providing higher system throughput without increasing the transmitted power or bandwidth requirements.

The invention of turbo codes and the re-discovery of sparse graph codes constitute a milestone in error-correction codes designed for communication and storage systems. Sparse graph codes such as low-density parity-check codes can offer a performance that approaches the previously elusive Shannon capacity with reasonable practical computational complexity. Fountain codes have emerged in the realm of sparse graph codes, and  have shown excellent performance for multicast and broadcast transmission without channel state information at the transmitter. A fountain code is inherently rateless, and as a consequence, such codes may potentially generate an unlimited number of encoded symbols on the fly. Thus due to the rateless property, these codes are suitable for transmission over time varying channels. The results presented in this thesis aim at providing insight into the fundamental design of rateless codes, which could serve as a guideline for the optimal design of rateless codes in real-world applications. The thesis is divided into two parts. The first part considers the analysis and design of rateless codes for point-to-point communication. To this end, we commence by considering the concatenation of Luby transform (LT) codes, which were the first practical realization of rateless codes, with differential modulators to exploit the inherent coding gain of differential modulations. An algorithm is developed based on the extrinsic information transfer (EXIT) chart to obtain optimized degree distributions of LT coded differential modulator systems in terms of convergence performance. Then, we delve deeper into the characteristics of LT codes with the objective of improving the error floor performance over noisy channels. An encoding scheme is proposed, which is subsequently used to reduce the error floor. To observe the consequences of the modified encoding scheme, the convergence behavior of the proposed LT code is analyzed using EXIT charts, and shown to be similar to the convergence performance of conventional LT codes. This idea is then extended to LT codes for transmission over erasure channels and a design framework is developed to jointly improve the transmission efficiency and erasure floor performance. For complexity-constrained applications, we construct low-complexity LT codes and devise a reduced-complexity LT decoder for transmission over noisy channels. The second part of the thesis deals with the analysis and design of rateless codes for multi-point communication. To address the shortcomings of existing distributed LT (DLT) codes, we introduce buffer-based DLT codes for a multi-source and multi-relay network to virtually convert lossy source-relay links to corresponding lossless links. We optimize the proposed DLT codes in terms of transmission efficiency; thus exhibiting better performance as compared to their conventional counterparts at the expense of increased computational complexity. The idea is then extended to a multi-way relay network where a linear-programming design framework is outlined for optimizing degree distributions in terms of transmission efficiency. Finally, a design framework is provided for DLT coding schemes, to jointly improve the transmission efficiency and erasure floor performance.

QC 20141202

A low-complexity method of interleaver design, sub-vector interleaving, for both parallel and serially concatenated convolutional codes (PCCCs and SCCCs, respectively) is presented here. Since the method is low-complexity, it is uniquely suitable for designing long interleavers. Sub-vector interleaving is based on a dynamical system representation of the constituent encoders employed by PCCCs and SCCCs. Simultaneous trellis termination can be achieved with a single tail sequence using sub-vector interleaving for both PCCCs and SCCCs. In the case of PCCCs, the error floor can be lowered by sub-vector interleaving which allows for an increase in the weight of the free distance codeword and the elimination of the lowest weight codewords generated by weight-2 terminating input sequences that determine the error floor at low signal-to-noise ratios (SNRs). In the case of SCCCs, sub-vector interleaving lowers the error floor by increasing the weight of the free distance codewords. Interleaver gain can also be increased for SCCCs by interleaving the lowest weight codewords from the outer into non-terminating input sequences to the inner encoder. Sub-vector constrained S-random interleaving, a method for incorporating S-random interleaving into sub-vector interleavers, is also proposed. Simulations show that short interleavers incorporating S-random interleaving into sub-vector interleavers perform as well as or better than those designed by the best and most complex methods for designing short interleavers. A method for randomly generating sub-vector constrained S-random interleavers that maximizes the spreading factor, S, is also examined. The convergence of the turbo decoding algorithm to maximum-likelihood decisions on the decoded input sequence is required to demonstrate the improvement in BER performance caused by the use of sub-vector interleavers. Convergence to maximum-likelihood decisions by the decoder do not always occur in the regions where it is feasible to generate the statistically significant numbers of error events required to approximate the BER performance for a particular coding scheme employing a sub-vector interleaver. Therefore, a technique for classifying error events by the mode of convergence of the decoder is used to illuminate the effect of the sub-vector interleaver at SNRs where it is possible to simulate the BER performance of the coding scheme.

The mathematical theory of communication has grown considerably since its inception 50 years ago. There are many problems that have been solved from the information theoretic perspective; yet remain open from the coding point of view. In particular, it is known what the optimum achievable performance of a certain system is, yet no practical coding scheme that achieves the optimal performance is known. This thesis is concerned with two such source coding problems: the Slepian-Wolf problem and the Wyner-Ziv problem. This thesis also investigates the related source coding problems of data compression and noise robust data compression.
A unified framework, based on the parallel concatenation of trellis structured codes (turbo codes) is applied and shown to perform well in all cases. This represents a break with traditional source coding techniques in that the code is fixed-length to fixed-length. As such, it is a probabilistic coding technique. An explicit joint design of the parallel concatenated codes, based on conditions rooted in information theory, is presented. The codes thus designed are intimately related to Latin squares and are therefore named Latin Square Based Codes. As opposed to the vast majority of the existing literature on turbo codes, these codes perform data compression and are designed jointly. Furthermore, they are non-binary, non-linear, non-systematic and non-symmetric.
In all the above cases, near Shannon limit performance is observed. For data compression as applied to binary memoryless sources, the scheme achieves reliable communication at a rate only 7.5% above the entropy of the source. A similar result is shown for the Slepian-Wolf problem. Noise robust compression is shown to be as close as 1.11 dB from capacity for AWGN channels while coding for the Wyner-Ziv problem is as close as 1.1 dB from the rate-distortion function.

Space-time convolutional code (STCC) is a technique that combines transmit diversity and coding to improve reliability in wireless fading channels. In this proposal, we demonstrate a systematic design of multi-level quadrature amplitude modulation (M-QAM) STCCs utilizing quadrature phase shift keying (QPSK) STCC as component codes for any number of transmit antennas. Morever, a low complexity decoding algorithm is introduced, where the decoding complexity increases linearly by the number of transmit antennas. The approach is based on utilizing a group interference cancellation technique also known as combined array processing (CAP) technique.

Finally, our research topic will explore: with the current approach, a scalable STTC with better performance as compared to space- time block code (STBC) combined with multiple trellis coded modulation (MTCM) also known as STBC-MTCM; the design of low complexity decoder for STTC; the combination of our approach with multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM).

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Os códigos IRA (Irregular Repeat-Accumulate) são uma classe de códigos criada com o objetivo de permitir codificação em tempo linear garantindo comunicação robusta a taxas próximas à capacidade do canal. Eles foram introduzidas por Jin, Khandekar and McEliece em 2000. O artigo no qual foram apresentados provou que os códigos IRA alcançavam a capacidade do canal de apagamento e mostravam desempenho cmparável ao dos códigos Turbo no canal AWGN (Additive White Gaussian Noise). Os desenvolvimentos teóricos por trás dos códigos IRA vieram da busca pelos primeiros códigos LDPC (Low Density Parity Check), ou códigos em grafos, que atingiriam a capacidade do canal AWGN. Os códigos LDPC - propostos originalmente por Robert Gallager em 1963 - se tornaram objeto de grande interesse nas últimas décadas após um longo período de ostracismo desde sua concepção, desenvolvendo seu potencial para codificação de canal em aplicações tão diversas quanto comunicações por satélite, redes sem fio e streaming via IP, bem como codificação distribuída de fonte. O objetivo desta dissertação é a avaliação dos códigos IRA e os efeitos de diferentes métodos de construção de grafos em seu desempenho. O uso das muitas variações do algoritmo PEG (Progressive Edge-Growth) foi testado em simulações no canal AWGN.
Irregular Repeat-Accumulate codes are motivated by the challenge of providing a class of codes that use linear-time encoding and decoding while communicating reliably at rates close to channel capacity. They were introduced by Hui Jin, Khandekar and McEliece in 2000, their article proves that IRA codes achieve channel capacity for the binary erasure channel and exhibit remarkably good performance on the AWGN channel. The theoretical developments supporting IRA codes stem from the efforts ar the development of capacity achieving Low-Density Parity-Check codes. LDPC codes were first proposed by Robert Gallager in 1963 and became the subject of intense research during the past decade after being dormant for a long period since its conception. Efforts by many researchers have developed its potential for channel coding in applications as diverse as satellite communications, wireless networks and streaming over IP, as well as studies on its usage in Distributed Source Coding. The goal of this dissertation is the evaluation of IRA codes and the effects of different graph construction methods in its performance. The use of the many variations of the Progressive Edge-Growth algorithm with IRA codes was tested in simulations on the AWGN channel.

The advent of performance-based codes in the United States underscores the need for a thorough, systematic approach to the documentation and accomplishment of a performance-based design. This project has three objectives: economic analysis of performance-based codes from a social view point, documentation of a performance-based design, and an example application of the ICC Performance-Based Code to high-rise office building. Economic issues explored include the externalities, insurance, and liabilities associated with performance-based codes. Documentation of a performance-based design includes delineation of the scope and goals with agreement between the designer, architect, building owner, and authority having jurisdiction, examination of the relevant code statutes, development of appropriate fire scenarios which meet the requirements of the performance matrices, thorough documentation of all design tool and calculation assumptions and limitations, and a clear demonstration of satisfactory accomplishment of stated goals and objectives. Finally, performance-based design alternatives to a prescriptively-designed 40 story office building were developed. There were three major design alternatives. The first design feature was the evacuation of occupants using elevators. The second alternative was the use of the assured fire safety system, which combined emerging technologies in fire detection, alarm, and suppression. The final design alternative was the routing of the domestic water supply through the sprinkler riser in order increase the reliability of the sprinkler system and save design, material, and installation costs associated with the domestic water supply risers. Finally, this project analyzed the specific life-cycle economic impact of the design alternatives when compared to the prescriptive design.

Sparse regression codes (SPARCs) are a recently introduced coding scheme for the additive white Gaussian noise channel, for which polynomial time decoding algorithms have been proposed which provably achieve the Shannon channel capacity. One such algorithm is the approximate message passing (AMP) decoder. However, directly implementing these decoders does not yield good empirical performance at practical block lengths. This thesis develops techniques for improving both the error rate performance, and the time and memory complexity, of the AMP decoder. It focuses on practical and efficient implementations for both single- and multi-user scenarios. A key design parameter for SPARCs is the power allocation, which is a vector of coefficients which determines how codewords are constructed. In this thesis, novel power allocation schemes are proposed which result in several orders of magnitude improvement to error rate compared to previous designs. Further improvements to error rate come from investigating the role of other SPARC construction parameters, and from performing an online estimation of a key AMP parameter instead of using a pre-computed value. Another significant improvement to error rates comes from a novel three-stage decoder which combines SPARCs with an outer code based on low-density parity-check codes. This construction protects only vulnerable sections of the SPARC codeword with the outer code, minimising the impact to the code rate. The combination provides a sharp waterfall in bit error rates and very low overall codeword error rates. Two changes to the basic SPARC structure are proposed to reduce computational and memory complexity. First, the design matrix is replaced with an efficient in-place transform based on Hadamard matrices, which dramatically reduces the overall decoder time and memory complexity with no impact on error rate. Second, an alternative SPARC design is developed, called Modulated SPARCs. These are shown to also achieve the Shannon channel capacity, while obtaining similar empirical error rates to the original SPARC, and permitting a further reduction in time and memory complexity. Finally, SPARCs are implemented for the broadcast and multiple access channels, and for the multiple description and Wyner-Ziv source coding models. Designs for appropriate power allocations and decoding strategies are proposed and are found to give good empirical results, demonstrating that SPARCs are also well suited to these multi-user settings.

This study presents information on the design procedure of seismic base isolation systems. Analysis of the seismic responses of isolated structures, which is oriented to give a clear understanding of the effect of base isolation on the nature of the structure
and discussion of various isolator types are involved in this work. Seismic isolation consists essentially of the installation of mechanisms, which decouple the structure, and its contents, from potentially damaging earthquake induced ground motions. This decoupling is achieved by increasing the horizontal flexibility of the system, together with providing appropriate damping. The isolator increases the natural period of the overall structure and hence decreases its acceleration response to earthquake-generated vibrations. This increase in period,together with damping, can reduce the effect of the earthquakes, so that smaller loads and deformations are imposed on the structure and its components. The key references that are used in this study are the related chapters of FEMA and IBC2000 codes for seismic isolated structures. In this work, these codes are used for the design examples of elastomeric bearings. Furthermore, the internal forces develop in the superstructure during a ground motion is determined
and the different approaches defined by the codes towards the &lsquo
scaling factor&rsquo
concept is compared in this perspective.

System för planering och bebyggelsekontroll måste hantera många utmaningar. Svårigheterna och den påverkan dessa system har på den fysiska miljön gör ämnet ständigt aktuellt att undersöka och försöka utveckla. Examensarbetet gör detta genom att jämföra systemet i Sverige med det i andra länder. Mer specifikt studeras form-based codes som förespråkas av Nyurbanismen i USA och design codes i England. I en svensk kontext kan dessa codes jämföras med detaljplanens planbestämmelser och riktlinjer i kvalitets- och gestaltningsprogram. I och med propositionen ”Politik för gestaltad Livsmiljö” som antogs i maj 2018 uppmuntras kommuner ta fram en arkitekturpolitik på lokal nivå. Dessa dokument utgör också ett intressant verktyg i sammanhanget. Examensarbetets frågeställning lyder därför: Hur kan koncept och verktyg från form-based codes i USA och design codes i England utveckla svenska kommuners arkitekturpolicyer, kvalitetsprogram och detaljplaner? I en mindre utsträckning har förutom systemen i USA och England även Frankrike och det typo-morfologiska förhållningsättet till zonering inkluderats. Examensarbetet startade med en litteraturstudie och åtföljdes av ett antal fallstudier som innefattade innehållsanalyser av arkitekturpolicyer, kvalitetsprogram och detaljplaner. De policyer som valdes ut för analys bedömdes ha mest gemensamt med arbetssätt inom form-based codes och design codes. Dessa var Örebros och Linköpings policyer samt Avesta, Fagerstas och Norbergs gemensamma policy. Från de två förstnämnda kommunerna analyserades även detaljplaner. Utöver detta inkluderades detaljplanerna och kvalitetsprogrammen för Henriksdalshamnen och Kolkajen i Stockholm. Innehållsanalysen av planer och program utgick från ett antal kategorier. Resultatet från fallstudierna jämfördes sedan med litteraturstudien. Parallellt genomfördes även en intervju med en praktiserande planarkitekt som innan intervjun fick läsa en begränsad mängd material om form-based codes. Resultat och analys från jämförelsen och intervjun låg sedan till grund för utformningen av ett antal rekommendationer. Litteraturstudien behandlade användningen av codes genom historien, utvecklingen och definitioner av form-based codes och design codes, samt hur dessa är organiserade. Vidare innefattade litteraturstudien kritik som riktats mot dessa och kopplingen till urbanmorfologi i relation till det franska typo-morfologiska förhållningsättet till zonering. Slutligen behandlades även utformnings och gestaltningsfrågor kopplat till bebyggelsereglering i den svenska planprocessen. Jämförelsen mellan innehållsanalysen av de utvalda fallen och litteraturstudien visade på skillnader och likheter mellan vad som behandlas och hur detta görs inom form-based codes och design codes respektive planer och program i Sverige. Resultatet från analysen av arkitekturpolicyerna visade på likheter med form-based codes och design codes som kunde förstärkas. I detta avseende utmärkte sig framför allt Örebros arkitekturstrategi som i likhet med praktiken inom form-based codes och design codes delade in staden i olika områdestyper. De två kvalitetsprogram som analyserades skiljde sig åt i karaktären vilket kopplades samman med processen för framtagandet av dessa. I jämförelse visade sig programmet för Kolkajen ha mer gemensamt med form-based codes och design codes än det för Henriksdalshamnen. Intervjun belyste perspektiv på innehållet i planer och program, kontexten som planer och program tas fram i och verkar, samt synpunkter på form-based codes.De rekommendationer som togs fram utgjordes av 19 aspekter som på ett övergripande plan kan behandlas för olika områdestyper i en arkitekturpolicy i likhet med Örebros arkitekturstrategi. Därutöver utvecklades en tabell med rekommendationer för vad som kan behandlas i detaljplaner och kvalitetsprogram beroende på planområdets läge i staden. Tanken är att dessa ska ha en direkt anknytning till områdestyperna i policyn då kopplingen mellan områdestyper och regleringar eller riktlinjer är direkt inom form-based codes och design codes. Genom att dessa preciseras i detaljplanerna skulle kopplingen vara mer flexibel än den är inom form-based codes. Detta skulle kunna innebära ett sätt för kommuner att agera proaktivt i stället för reaktivt till enskilda exploateringsförslag. Slutligen visade även litteraturstudien fördelar med att tillämpa enkla, principiella illustrationer vilket kan göras i en större utsträckning i såväl policyer, program och detaljplaner.
Planning and development control systems must deal with many challenges. The difficulties and the impact these systems have on the physical environment make the subject constantly relevant to study and try to develop. The thesis does this by comparing the system in Sweden with that in other countries, more specifically form-based codes advocated by New Urbanism in the US and design codes in England. In a Swedish context, these codes can be compared with the building control regulations in detailed plans and guidelines in quality and design programs. With the adoption of the Government bill "Politik för gestaltad livsmiljö" in May 2018, municipalities are encouraged to develop an architectural policy at the local level. These documents are also an interesting tool in this context. The thesis’ question therefore reads: How can concepts and tools from form-based codes in the US and design codes in England develop Swedish municipalities’ architecture policies, quality programs and detailed plans? To a lesser extent, in addition to the systems in the US and England, France and the typo-morphological approach to zoning have also been included. The degree project started with a literature study and was accompanied by a few case studies that included content analysis of architectural policies, quality programs and detailed plans. The policies selected for analysis were judged to have the most in common with approaches to regulations within form-based codes and design codes. These were Örebro's and Linköping's policies and Avesta, Fagersta and Norberg’s joint policy. Detailed plans were also analysed from the first two municipalities. In addition to this, the detailed plans and quality programs for Henriksdalshamnen and Kolkajen in Stockholm were included. The content analysis of plans and programs was based on a few categories. The results from the case studies were then compared with the literature study. In parallel, an interview was also conducted with a practicing planning architect who before the interview read a limited amount of material about form-based codes. Results and analysis from the comparison and the interview then formed the basis for the formulation of recommendations.The literature study dealt with the use of codes throughout the history, the development and definitions of form-based codes and design codes, as well as how these are organized. Furthermore, the literature study included criticism of these and the connection to urban morphology in relation to the French typo-morphological approach to zoning. Finally, design issues linked to building regulation were also dealt with in the Swedish planning process. The comparison between the content analysis of the selected cases and the literature study showed differences and similarities between what is treated and how this is done within form-based and design codes and plans and programs in Sweden. The results from the analysis of the architecture policies showed similarities with form-based codes and design codes that could be strengthened. In this respect, Örebro’s architectural strategy especially distinguished, which, like the practice in form-based codes and design codes, divided the city into different area types. The two quality programs that were analysed differed in nature, which was linked to the process in which they were designed. In comparison, the program for Kolkajen turned out to have more in common with form-based codes and design codes than the program for Henriksdalshamnen. The interview shed light on perspectives on the content of plans and programs, the context in which plans, and programs are produced and operate as well as views on form-based codes. The recommendations developed consisted of 19 aspects. These can be dealt with at an overall level for different area types in an architecture policy like Örebro’s architecture strategy. In addition, a table was developed with recommendations for what can be dealt with in detailed plans and quality programs depending on the location of the area in the city. The idea is that these should have a direct connection to the area types in the policy like form-based codes and design codes, but a more flexible one as the area type should be more precisely defined in the detail plan. This could offer a way for municipalities to act proactively instead of reactively to individual development proposals. Finally, the literature study also showed the advantages of applying simple, principled illustrations, which can be done to a greater extent in policies, programs, and detailed plans in Sweden.

The concept sustainable development is defined as meeting the needs of the existing global population without compromising the opportunities for future generations to also meet their needs. Therefore, in order to work towards sustainable development, active sustainable choices need to be made in a company’s business activities. This thesis has a qualitative approach that aims to study five different Swedish textile companies and how they work towards sustainable development in their code of conduct for suppliers. Theories are collected from literature, articles and web sources, which include sustainable development, social, environmental and economic sustainability and codes of conduct. The main target is to identify different sustainable approaches towards sustainable development in the code of conduct for suppliers focusing on the social, environmental and economic sustainability. The empirical data is collected from five personal interviews with representatives in charge of sustainable activities from the selected companies. The result of the study confirms that all companies to different extents are working towards sustainable development in their code of conduct for suppliers. Sustainable approaches in these codes are agreements with suppliers including following the country’s laws and regulations of the suppliers. The companies also collaborate with third-party industrial research institutes to reduce water and chemical supply in the production. Moreover, the study shows that the concept sustainable development seems to be less embedded in the code of conduct for suppliers. Companies rather work with sustainable activities in forms of running projects and establishing agreements beyond having a code of conduct.
Program: Master programme in Applied Textile Management

Philosophiae Doctor - PhD (Mathematics)
The main theme of this thesis is the construction of linear codes from adjacency matrices or sub-matrices of adjacency matrices of regular graphs. We first examine the binary codes from the row span of biadjacency matrices and their transposes for some classes of bipartite graphs. In this case we consider a sub-matrix of an adjacency matrix of a graph as the generator of the code. We then shift our attention to uniform subset graphs by exploring the automorphism groups of graph covers and some classes of uniform subset graphs. In the sequel, we explore equal codes from adjacency matrices of non-isomorphic uniform subset graphs and finally consider codes generated by an adjacency matrix formed by adding adjacency matrices of two classes of uniform subset graphs.

We introduced nested search methods to design (n, k) block codes for arbitrary channels by optimizing an appropriate metric spectrum in each iteration. For a given k, the methods start with a good high rate code, say k/(k + 1), and successively design lower rate codes up to rate k/2^k corresponding to a Hadamard code. Using a full search for small binary codes we found that optimal or near-optimal codes of increasing length can be obtained in a nested manner by utilizing Hadamard matrix columns. The codes can be linear if the Hadamard matrix is linear and non-linear otherwise. The design methodology was extended to the generic complex codes by utilizing columns of newly derived or existing unitary codes. The inherent nested nature of the codes make them ideal for progressive transmission. Extensive comparisons to metric bounds and to previously designed codes show the optimality or near-optimality of the new codes, designed for the fading and the additive white Gaussian noise channel (AWGN). It was also shown that linear codes can be optimal or at least meeting the metric bounds; one example is the systematic pilot-based code of rate k/(k + 1) which was proved to meet the lower bound on the maximum cross-correlation. Further, the method was generalized such that good codes for arbitrary channels can be designed given the corresponding metric or the pairwise error probability. In synchronous multiple-access schemes it is common to use unitary block codes to transmit the multiple users’ information, especially in the downlink. In this work we suggest the use of newly designed non-unitary block codes, resulting in increased throughput efficiency, while the performance is shown not to be substantially sacrificed. The non-unitary codes are again developed through suitable nested searches. In addition, new multiple-access codes are introduced that optimize certain criteria, such as the sum-rate capacity. Finally, the introduction of the asymptotically optimum convolutional codes for a given constraint length, reduces dramatically the search size for good convolutional codes of a certain asymptotic performance, and the consequences to coded code-division multiple access (CDMA) system design are highlighted.

We investigate the design of Raptor codes---a class of fountain codes---over Gaussian channels. In this thesis, we prove that there exists no universal choice of input degree distribution or constructing capacity-achieving Raptor codes using mean-LLR, EXIT chart approach. An approach of finding input and output degree distribution jointly is proposed. Through the codes constructed by this approach, we show our approach uniformly outperforms an existing heuristic approach over all Gaussian channels. However, there still exists a gap to channel capacity for Raptor codes constructed by mean-LLR. EXIT chart based approach.

Among the recent advances in the area of low-density parity-check (LDPC) codes, protograph-based LDPC codes have the advantages of a simple design procedure and highly structured encoders and decoders. These advantages can also be exploited in the design of protograph-based generalized LDPC (G-LDPC) codes. In this dissertation we provide analytical tools which aid the design of protograph-based LDPC and G-LDPC codes. Specifically, we propose a method for computing the codeword-weight enumerators for finite-length protograph-based G-LDPC code ensembles, and then we consider the asymptotic case when the block-length goes to infinity. These results help the designer identify good ensembles of protograph-based G-LDPC codes in the minimum distance sense (i.e., ensembles which have minimum distances grow linearly with code length). Furthermore, good code ensembles can be characterized by good stopping set, trapping set, or pseudocodeword properties, which assist in the design of G-LDPC codes with low floors. We leverage our method for computing codeword-weight enumerators to compute stopping-set, and pseudocodeword enumerators for the finite-length and the asymptotic ensembles of protograph-based G-LDPC codes. Moreover, we introduce a method for computing trapping set enumerators for finite-length (and asymptotic) protograph-based LDPC code ensembles. Trapping set enumerators for G-LDPC codes represents a more complex problem which we do not consider here. Inspired by our method for computing trapping set enumerators for protograph-based LDPC code ensembles, we developed an algorithm for estimating the trapping set enumerators for a specific LDPC code given its parity-check matrix. We used this algorithm to enumerate trapping sets for several LDPC codes from communication standards. Finally, we study coded-modulation schemes with LDPC codes and pulse position modulation (LDPC-PPM) over the free-space optical channel. We present three different decoding schemes and compare their performances. In addition, we developed a new density evolution tool for use in the design of LDPC codes with good performances over this channel.

Low-density parity-check (LDPC) codes have been intensively studied in the past decade for their capacity-approaching performance. LDPC code implementation complexity and the error-rate floor are still two significant unsolved issues which prevent their application in some important communication systems. In this dissertation, we make efforts toward solving these two problems by introducing the design of a class of LDPC codes called structured irregular repeat-accumulate (S-IRA) codes. These S-IRA codes combine several advantages of other types of LDPC codes, including low encoder and decoder complexities, flexibility in design, and good performance on different channels. It is also demonstrated in this dissertation that the S-IRA codes are suitable for rate-compatible code family design and a multi-rate code family has been designed which may be implemented with a single encoder/decoder.The study of the error floor problem of LDPC codes is very difficult because simulating LDPC codes on a computer at very low error rates takes an unacceptably long time. To circumvent this difficulty, we implemented a universal quasi-cyclic LDPC decoder on a field programmable gate array (FPGA) platform. This hardware platform accelerates the simulations by more than 100 times as compared to software simulations. We implemented two types of decoders with partially parallel architectures on the FPGA: a circulant-based decoder and a protograph-based decoder. By focusing on the protograph-based decoder, different soft iterative decoding algorithms were implemented. It provides us with a platform for quickly evaluating and analyzing different quasi-cyclic LDPC codes, including the S-IRA codes. A universal decoder architecture is also proposed which is capable of decoding of an arbitrary LDPC code, quasi-cyclic or not. Finally, we studied the low-floor problem by focusing on one example S-IRA code. We identified the weaknesses of the code and proposed several techniques to lower the error floor. We successfully demonstrated in hardware that it is possible to lower the floor substantially by encoder and decoder modifications, but the best solution appeared to be an outer BCH code.

Recent advancements in iterative processing have allowed communication systems to perform close to capacity limits withmanageable complexity.For manychannels such as the AWGN and flat fading channels, codes that perform only a fraction of a dB from the capacity have been designed in the literature. In this dissertation, we will focus on the design and analysis of near-capacity achieving codes for another important class of channels, namely inter-symbol interference (ISI)channels. We propose various coding schemes such as low-density parity-check (LDPC) codes, parallel and serial concatenations for ISI channels when there is no spectral shaping used at the transmitter. The design and analysis techniques use the idea of extrinsic information transfer (EXIT) function matching and provide insights into the performance of different codes and receiver structures. We then present a coding scheme which is the concatenation of an LDPC code with a spectral shaping block code designed to be matched to the channel??s spectrum. We will discuss how to design the shaping code and the outer LDPC code. We will show that spectral shaping matched codes can be used for the parallel concatenation to achieve near capacity performance. We will also discuss the capacity of multiple antenna ISI channels. We study the effects of transmitter and receiver diversities and noisy channel state information on channel capacity.

In this thesis, we investigate the optimization of Raptor codes for various channels of interest in practical wireless systems. First, we present an analytical asymptotic analy- sis of jointly decoded Raptor codes over a BIAWGN channel. Based on the analysis, we derive an optimization method for the design of efficient output degree distributions. We show that even though Raptor codes are not universal on other channels than the BEC, Raptor code optimized for a given channel capacity also perform well on a wide range of channel capacities when joint decoding is considered. Then, we propose a rate splitting strategy that is efficient for the design of finite length Raptor codes. We next investigate the extension of the analysis to the uncorrelated Rayleigh-fading chan- nel with perfect channel state information (CSI) at the receiver, and optimize Raptor codes for quasi-static fading channels when CSI is available at the receiver but not at the transmitter. Finally, we show that in presence of imperfect CSI at the receiver, it is possible to improve the performance with no additional complexity, by using an appropriate metric for the computation of the LLR at the output of the channel. In the second part of this thesis, we investigate the construction of efficient finite length LDPC codes. In particular, we present some improvements for the Progressive Edge- Growth algorithm that allow to construct minimal graphs. The proposed algorithm is used to construct protographs with large girth that perform well under iterative decoding. Moreover, we propose an efficient structured search procedure for the design of quasi-cyclic LDPC codes.

The main objective of the thesis is evaluating and comparing Second-Order Elastic Analysis Methods defined in two different specifications, AISC 2005 and TS648 (1980). There are many theoretical approaches that can provide exact solution for the problem. However, approximate methods are still needed for design purposes. Simple formulations for code applications were developed, and they are valid as acceptable results can be obtained within admissible error limits. Within the content of the thesis, firstly background information related to second-order effects will be presented. The emphasis will be on the definition of geometric non-linearity, also called as P-&
#948
and P-&
#916
effects. In addition, the approximate methods defined in AISC 2005 (B1 &ndash
B2 Method), and TS648 (1980) will be discussed in detail. Then, example problems will be solved for the demonstration of theoretical formulations for members with and without end translation cases. Also, the results obtained from the structural analysis software, SAP2000, will be compared with the results acquired from the exact and the approximate methods. Finally, conclusions related to the study will be stated.

Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2007.
Committee Chair: McLaughlin, Steven; Committee Member: Barry, John; Committee Member: Boldyreva, Alexandra; Committee Member: Clements, Mark; Committee Member: Li, Ye.

Polar codes are a new class of forward error-correcting codes recently discovered by Arıkan. They are the first codes with an explicit construction to provably achieve capacity, a theoretical limit governing the transmission of information in the presence of noise, for a wide variety of communication channels. Since polar codes have a very regular construction, they also lend themselves very well to hardware implementations. This thesis presents the design work underlying the development of two generations of hardware decoders for polar codes based upon the successive-cancellation algorithm. Making use of SRAM-based semi-parallel architectures, those designs allow very large polar codes to be implemented on Altera Stratix IV and Stratix V FPGA targets: up to N=2^17 for the first generation, and N=2^21 for the second-generation design. The second-generation decoder also features variable quantization levels to reduce its memory footprint, look-ahead to improve throughput, a redesigned partial-sum encoder based on a novel semi-parallel design for increased scalability, and an overlapped frame loading mechanism allowing full-speed operation of the decoder with a single input buffer.
Les codes polaires constituent une nouvelle classe de codes correcteurs d'erreurs sans voie de retour (forward error correction) découverte récemment par Arıkan. Ce sont les premiers codes ayant une construction explicite à atteindre la capacité du canal, une limite théorique s'appliquant à l'envoi d'information sur un canal en présence de bruit, et ce pour de nombreux types de canaux. La construction très régulière des codes polaires simplifie la conception de décodeurs matériels. Ce mémoire présente deux générations de décodeurs matériels pour les codes polaires basés sur l'algorithme d'annulation successive. À l'aide d'une architecture partiellement parallèle s'appuyant sur des mémoires SRAM, ces décodeurs permettent la synthèse de codes polaires très longs. Sur des FPGAs Altera Stratix IV et Stratix V, nous avons pu synthétiser des décodeurs de taille N=2^17 pour la première génération et N=2^21 pour la seconde. Afin d'atteindre cette taille de codes, la seconde génération de décodeurs s'appuie entre autres sur une quantification variable afin de réduire son empreinte mémoire, sur un circuit de génération de sommes partielles novateur, sur une technique de décodage anticipé pour améliorer son débit et sur un chargement chevauché des trames pour atteindre son débit maximal sans registres d'entrée additionnels.

Thesis (M.Sc.Eng.) PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.
In this thesis, we firstly present the secure multipliers protected by the AMD codes, and demonstrate that the fault masking probabilities are not worse than the results based on the theoretical analysis of error masking probabilities, if the attacker injects faults at outputs of the inside logic gates of the protected devices. Single-errorcorrecting, double-error-detecting (SEC-DED) codes are widely used for the design of errors, thus they are not suitable for memories used in cryptographic devices. Algebraic Manipulation Detection (AMD) codes provide strong protection against fault injection attacks. But traditional AMD codes can not be used for correcting errors. In this thesis, we also present the constructions of the strongly secure algebraic manipulation correction (AMC) codes. The estimation for a probability for miscorrection of multiple errors is given. Hardware implementations of strongly secure SEC-DED memories based on the proposed codes are presented. Comparison with other codes which have been used for SEC-DED memories with security or weak security are given in terms of numbers of undetected errors, sizes of security kernels and miscorrection probabilities as well as latency, area and power consumption for encoders and decoders. An error handling method to distinguish between random errors and fault injection attacks is presented as well. The proposed code can be applied to most secure-critical memories in cryptographic devices. As far as we know, this is the only efficient approach to provide both high reliability for single and double random errors, and high security for strong fault attack when an attacker has a control of both on the messages (outputs of the memories) and the errors.
2031-01-01

The ideas within this thesis are meant to clarify my explorations, research and painting practice during my studies at Virginia Commonwealth University. I expand on my general statements about being fascinated by advancing technologies and concerned about the after effects of these advancements. The writing explores my curiosity about the internal, skeletal structure of things and how they operate. I explain how the paintings are idiosyncratic hybrids that evoke animation, imaginary scientific propositions, blueprints, maps, and advancing technologies. The work combines these interests with my observations of day-to-day experiences. Isolated events provide found compositions which I then manipulate: a seemingly mundane bike ride gets mapped into a well–ordered schematic of social interaction.

The conception of turbo codes by Berrou et al. has created a renewed interest in modern graph-based codes. Several encouraging results that have come to light since then have fortified the role these codes shall play as potential solutions for present and future communication problems. This work focuses on both practical and theoretical aspects of graph-based codes. The thesis can be broadly categorized into three parts. The first part of the thesis focuses on the design of practical graph-based codes of short lengths. While both low-density parity-check codes and rateless codes have been shown to be asymptotically optimal under the message-passing (MP) decoder, the performance of short-length codes from these families under MP decoding is starkly sub-optimal. This work first addresses the structural characterization of stopping sets to understand this sub-optimality. Using this characterization, a novel improved decoder that offers several orders of magnitude improvement in bit-error rates is introduced. Next, a novel scheme for the design of a good rate-compatible family of punctured codes is proposed. The second part of the thesis aims at establishing these codes as a good tool to develop reliable, energy-efficient and low-latency data dissemination schemes in networks. The problems of broadcasting in wireless multihop networks and that of unicast in delay-tolerant networks are investigated. In both cases, rateless coding is seen to offer an elegant means of achieving the goals of the chosen communication protocols. It was noticed that the ratelessness and the randomness in encoding process make this scheme specifically suited to such network applications. The final part of the thesis investigates an application of a specific class of codes called network codes to finite-buffer wired networks. This part of the work aims at establishing a framework for the theoretical study and understanding of finite-buffer networks. The proposed Markov chain-based method extends existing results to develop an iterative Markov chain-based technique for general acyclic wired networks. The framework not only estimates the capacity of such networks, but also provides a means to monitor network traffic and packet drop rates on various links of the network.

Brands are now more aware of the importance of implementing a mobile marketing strategy by employing a QR code campaign with the intent of enhancing brand awareness and strength the relationship with customers. Thus, an extensive research has been conducted on this subject with focus on the Swedish premium fashion market .The purpose of this research study is to analyze a new mobile marketing tool called Quick-response (QR) codes, and understand this phenomenon on the premiumfashion segment in Sweden, while relating at the same time with concepts such as customer relationship management and brand awareness. In this study a qualitative research method was chosen, by applying qualitative semi-structured interviews and qualitative content analysis.The research shows that there is a problem with customers' awareness regarding QR codes and its usage. Companies should also be educated for the importance of integrating a mobile marketing program within their marketing and communication strategy. Nonetheless, the study has shown that brands may increase brand awareness and drive CRM if all the requirements above stated are fulfilled, since all of the participants in this research acknowledge the relationship between a brand and its customers extremely important.
Program: Master in Fashion Management with specialisation in Fashion Marketing and Retailing

Throughout history planning codes and standards have been used to regulate the built environment for health, power, order, and economic reasons. More recently, in the urban design and planning field, planning codes and standards have emerged to become tools in the process of “placemaking”. The concept of placemaking builds from the desire of humans to create places, not spaces, which are unique, attractive, identifiable, and memorable. It is a concept that is comprised of visual and social components, recognizing the need for both in the creation of successful places. In the field of urban design and planning, form-based codes (FBCs) and design guidelines have emerged to become two types of planning tools used in the process of placemaking. This study explores the relationship between FBCs, design guidelines, and placemaking, investigating it through an extensive literature review, and then in the context of the case of Hayward, California through an update of the City’s Downtown design requirements and guidelines. To frame the update of the Hayward’s Downtown design requirements and guidelines this study used an exploratory methodology that combined quantitative and qualitative methods. Archival research was conducted to provide a historical narrative of the City and the Downtown area and a documents analysis was conducted to reveal information about existing Downtown policies and programs. Community participation through the crowdsourcing platform of MindMixer was used to collect community input and feedback about concepts of place in Downtown. The data analysis and findings from these methods were combined with findings from the literature review to formulate recommendations that were used in the update of Hayward’s Downtown design requirements and guidelines document. Keywords:

In this thesis, we describe linear codes over prime fields obtained from incidence designs of iterated line graphs of complete graphs Li(Kn) where i = 1, 2. In the binary case, results are extended to codes from neighbourhood designs of the line graphs Li+1(Kn) using certain elementary relations. Codes from incidence designs of complete graphs, Kn, and neighbourhood designs of their line graphs, L1(Kn) (the so-called triangular graphs), have been considered elsewhere by others. We consider codes from incidence designs of L1(Kn) and L2(Kn), and neighbourhood designs of L2(Kn) and L3(Kn). In each case, basic parameters of the codes are determined. Further, we introduce a family of vertex-transitive graphs 􀀀n that are embeddable into the strong product L1(Kn) ⊠ K2, of triangular graphs and K2, a class which at first sight may seem unnatural but, on closer look, is a repository of graphs rich with combinatorial structures. For instance, unlike most regular graphs considered here and elsewhere that only come with incidence and neighbourhood designs, 􀀀n also has what we have termed as 6-cycle designs. These are designs in which the point set contains vertices of the graph and every block contains vertices of a 6-cycle in the graph. Also, binary codes from incidence matrices of these graphs have other minimum words in addition to incidence vectors of the blocks. In addition, these graphs have induced subgraphs isomorphic to the family Hn of complete porcupines (see Definition 4.11). We describe codes from incidence matrices of 􀀀n and Hn and determine their parameters.

The problem of the efficient use of Hybrid Automatic-Repeat-reQuest (Hybrid-ARQ) in wireless communication has attracted a considerable amount of research. In this thesis, the use and implementation of turbo codes as the Forward Error Correction (FEC) code for Hybrid-ARQ is investigated. The major accomplishments of the research include both the analysis and implementation of turbo Hybrid-ARQ. The thesis begins by obtaining a tractable bound for the performance of turbo codes with M-ary Quadrature-Amplitude-Modulation (M-ary QAM). The research considers the design problem of turbo coded Hybrid-ARQ optimized for AWGN and fading channels. The design problem of turbo Hybrid-ARQ in wideband channels is considered and an optimization strategy is proposed based on Orthogonal-Frequency-Division- Multiplexing (OFDM). The research also presents a novel rate scalable encoder structure that optimal selects a disparate but optimal pair of component codes given the channel conditions. A second part of the thesis considers the implementation of turbo Hybrid-ARQ in Very Large Scale Integration (VLSI ) systems. A design for a single architecture for Type-I and Type-II turbo Hybrid-ARQ is suggested in addition to approaches for improving performance of the Soft-Output-Viterbi-Algorithm(SOVA) decoder core. The research also proposes a SOVA decoder architecture that exploits reliability information to select between the SOVA and bi-directional SOVA.

In Shannon’s seminal paper, “A Mathematical Theory of Communication”, he defined ”Channel Capacity” which predicted the ultimate performance that transmission systems can achieve and suggested that capacity is achievable by error-correcting (channel) coding. The main idea of error-correcting codes is to add redundancy to the information to be transmitted so that the receiver can explore the correlation between transmitted information and redundancy and correct or detect errors caused by channels afterward. The discovery of turbo codes and rediscovery of Low Density Parity Check codes (LDPC) have revived the research in channel coding with novel ideas and techniques on code concatenation, iterative decoding, graph-based construction and design based on density evolution. This dissertation focuses on the design aspect of graph-based channel codes such as LDPC and Irregular Repeat Accumulate (IRA) codes via density evolution, and use the technique (density evolution) to design IRA codes for scalable image/video communication and LDPC codes for distributed source coding, which can be considered as a channel coding problem. The first part of the dissertation includes design and analysis of rate-compatible IRA codes for scalable image transmission systems. This part presents the analysis with density evolution the effect of puncturing applied to IRA codes and the asymptotic analysis of the performance of the systems. In the second part of the dissertation, we consider designing source-optimized IRA codes. The idea is to take advantage of the capability of Unequal Error Protection (UEP) of IRA codes against errors because of their irregularities. In video and image transmission systems, the performance is measured by Peak Signal to Noise Ratio (PSNR). We propose an approach to design IRA codes optimized for such a criterion. In the third part of the dissertation, we investigate Slepian-Wolf coding problem using LDPC codes. The problems to be addressed include coding problem involving multiple sources and non-binary sources, and coding using multi-level codes and nonbinary codes.

Since the rediscovery, LDPC codes attract a large amount of research efforts. In 1998, nonbinary LDPC codes were firstly investigated and the results shown that they are better than their binary counterparts in performance. Recently, there is always a requirement from the industry to design applied nonbinary LDPC codes. In this dissertation, we firstly propose a novel class of quasi-cyclic (QC) LDPC codes. This class of QC-LDPC codes embraces both linear encoding complexity and excellent compatibility in various degree distributions and nonbinary expansions. We show by simulation results that our proposed QC-LDPC codes perform as well as their comparable counterparts. However, this proposed code structure is more flexible in designing. This feature may show its power when we change the code length and rate adaptively. Further more, we present two algorithms to generate codes with short girth and better girth distribution. The two algorithms are designed based on progressive edge growth (PEG) algorithm and they are specifically designed for quasi-cyclic structure. The simulation results show the improvement they achieved. In this thesis, we also investigate the believe propagation based iterative algorithms for decoding of nonbinary LDPC codes. The algorithms include sum-product (SP) algorithm, SP algorithm using fast Fourier transform, min-sum (MS) algorithm and complexity reduced extended min-sum (EMS) algorithm. In particular, we present the proposed modified min-sum algorithm with threshold filtering which further reduces the computation complexity.

碩士
中興大學
電機工程學系所
95
The wireless channel suffers severe attenuation caused by multipath fading. The effective technique to mitigate multipath fading is to use the time or frequency diversity. The communication system with multiple input multiple output can combat the channel attenuation by spatial diversity and increase the channel information capacity. The principle of space-time coding schemes is to combine the concept of channel coding design and multiple transmit antennas, which are then effectively applied to multipath wireless channel. Since the amount of data transfer of the modern digital or mobile communication is increasing, the reliability of the data transfer has become more and more important. Therefore, the error correction coding has played a very important role in wireless communication channel. The turbo code is one of the most popular error correction codes at present due to its good error correction ability. Besides, the turbo code is adopted in the 3G mobile communication standard. In this thesis, we present the application of several important concepts of wireless digital communications, i.e., serial concatenation, turbo coding, and temporal and antenna diversity . We combine the turbo code and the space-time block code and use the LogMAP algorithm to implement the soft in/soft out decoding algorithms of turbo code. Finally, we present our simulation results under different encoding scheme of the space time block code. Furthermore, we also present the comparison of the simulation result under different rate of space-time block codes but the same number of transmit antennas.

In a constant weight code, each code word contains a constant number of 1's. If this number is equal to half the length of the code word then the code is called balanced. These codes find many applications in computer and communication systems noise reduction in VLSI systems, fault masking in bus lines of VLSI systems, rejection of the low frequency components in digital communication systems, delay insensitive communications in asynchronous systems, data transmission in fiber optics, data storage in optical discs and magnetic tapes, fault tolerant synchronous circuits, etc. This thesis presents new efficient design methods for constant weight codes suitable to these applications. The proposed codes require low redundancy but at the same time have fast and simple encoding/decoding algorithms.
Graduation date: 1997

碩士
國立中山大學
通訊工程研究所
93
In this thesis, we propose a new way to generate orthogonal code distinct from complete complementary (CC) code and Super CC code but it still have ideal auto-correlation and cross-correlation property. We also introduce the concept of correlation and propose six rules to determine if the code generated by different ways are the same.After that we use the rules on orthogonal matrix and find a new way to generate orthogonal matrix different from Hadamard marix. Then we will use this marix in 2-D orthogonal variable spreading factor (OVSF) code and generate similar codes.