Turbo-codes have attracted an explosion of interest since their discovery in 1993: for the first time, the gap with the limits predicted by information and coding theory was on the way to be bridged. The astonishing performance of turbo-codes relies on two major concepts: code concatenation so as to build a powerful global code, and iterative decoding in order to efficiently approximate the optimal decoding process. As a matter of fact, the techniques involved in turbo coding and in the associated iterative decoding strategy can be generalized to other problems frequently encountered in digital communications. This results in a so-called turbo principle. A famous application of the latter principle is the communication scheme referred to as turbo-equalization: when considering coded transmission over a frequency-selective channel, it enables to jointly and efficiently perform the equalization and decoding tasks required at the receiver. This leads by the way to significant performance improvement with regard to conventional disjoint approaches. In this context, the purpose of the present thesis is the derivation and the performance study of novel digital communication receivers, which perform iterative joint detection and decoding by means of the turbo principle. The binary turbo-equalization scheme is considered as a starting point, and improved in several ways, which are detailed throughout this work. Emphasis is always put on the performance analysis of the proposed communication systems, so as to reach insight about their behavior. Practical considerations are also taken into account, in order to provide realistic, tractable, and efficient solutions.

This study examined the unique contributions of morphological awareness and phonological recoding to word decoding, reading comprehension, and reading vocabulary for 197 Spanish-speaking English language learners enrolled in the fifth grade. The study also explored the contribution of phonological recoding, measured by accuracy on a pseudo-word decoding task, to the prediction of the same components of reading achievement. Specifically the study explored whether the contribution of phonological recoding changed when morphological awareness and oral vocabulary (a mediator of reading achievement) were added as predictors. To examine unique contributions, morphological awareness was separated from phonological and orthographic confounds present in opaque morphological relationships by using structural equation modeling to construct a latent variable stemming from the shared variance of four morphological tasks with different levels of morphological transparency, and therefore different phonological and orthographic processing demands. A latent variable of phonological recoding was also created. Findings indicated that when controlling for phonological recoding, morphological awareness made a significant and meaningful contribution to passage comprehension and reading vocabulary, but not word decoding with oral vocabulary acting as a significant mediator of this relationship. The study also found that phonological recoding was a significant predictor of each reading outcome when morphological awareness was not included as a predictor, but only significantly predicted word reading when controlling for morphological awareness. Significance of these findings to research and the need for additional morphological instruction within educational settings are discussed.

The general aim of this thesis was to examine variations in the word decoding skills of reading disabled children. These variations were related to possible cognitive, developmental, and environmental causes of reading disability. Possible implications for educational interventions were also analysed. The thesis critically examines the inclusion of the concept of intelligence in the definition of developmental dyslexia. It is suggested that variations in word decoding skills should offer a more solid basis for a study of varieties of reading disability. The empirical studies showed that a) in young children there was a shift from phonological to orthographic word decoding; b) phonological type children (weak in phonological decoding) were characterised by specific phonological deficits; c) surface type children (weak in orthographic decoding) showed more global cognitive deficits suggesting a general developmental delay; d) surface type children showed impaired visual implicit memory for words, which might be associated with limited print exposure; e) an improvement in phonological awareness only transferred to an improved text reading ability for some reading disabled children; f) children who did not benefit from a phonological intervention seemed to rely on orthographic word decoding in text reading. Thus, the thesis suggests that variations in phonological and orthographic word decoding skills offer a useful basis for the study of varieties of reading disability and that educational interventions should pay regard to what the child is already attempting to do when reading. / On the day of the defence date the status of article IV was: Manuscript.

We study the problem of list decoding with focus on the case when we have a list size limited to two. Under this restriction we derive general lower bounds on the maximum possible size of a list-of-2-decodable code. We study the set of correctable error patterns in an attempt to obtain a characterization. For a special family of Reed-Solomon codes - which we identify and name 'class-I codes' - we give a weight-based characterization of the correctable error patterns under list-of-2 decoding. As a tool in this analysis we use the theoretical framework of Sudan's algorithm. The characterization is used in an exact calculation of the probability of transmission error in the symmetric channel when list-of-2 decoding is used. The results from the analysis and complementary simulations for QAM-systems show that a list-of-2 decoding gain of nearly 1 dB can be achieved. Further we study Sudan's algorithm for list decoding of Reed-Solomon codes for the special case of the class-I codes. For these codes algorithms are suggested for both the first and second step of Sudan's algorithm. Hardware solutions for both steps based on the derived algorithms are presented.

I den här uppsatsen har vi studerat hur en film aktiverar människors sociala och kulturella positioner. Vi visade filmen Crash för åtta komvuxelever, vilket följdes av en kvalitativ intervju med dem. Eleverna fick svara på frågor om sin egen bakgrund, filmens budskap och rollfigurer, hur de uppfattade filmen och den föreslagna verkligheten i filmen, samt frågor kring sin egen framtid. Informanternas svar har hjälpt oss att synliggöra hur det görs över- och underordningar i filmen. Med hjälp av vår bakgrund och analytiska verktyg har vi interagerat med våra informanter och de har bidragit med perspektiv som vi aldrig hade kunnat se med tillämpning av enbart teorier. Något som blev framträdande var att de applicerade problematiken som den amerikansktillverkade filmen tar upp, på ett svenskt samhälle. Vi kom fram till att filmen som populärkulturellt medel hjälper till att reproducera gamla maktordningar och fördomar. Trots att detta inte var filmskaparens intention, blir det här till fördomar och stereotypa föreställningar om att det finns rasskillnader. Med den här studien har vi synliggjort att filmen medverkar till att reproducera maktordningar. Film och dess folkliga inflytande, skulle kunna bli ett redskap för nytänkande runt klass, kön och etnicitet med mera.

We consider transmission over a binary erasure wiretap channel using the code construction method introduced by Rathi et al. based on two edge type Low-Density Parity-Check (LDPC) codes and the coset encoding scheme. By generalizing the method of computing conditional entropy for standard LDPC ensembles introduced by Méasson, Montanari, and Urbanke to two edge type LDPC ensembles, we show how the equivocation for the wiretapper can be computed. We find that relatively simple constructions give very good secrecy performance and are close to the secrecy capacity. / <p>Copyright 2010 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works. QC 20120110</p>

The purpose of this study was to investigate methods for improving reading comprehension among struggling adolescent readers. More specifically, this study was concerned with: the effectiveness of pull-out intervention for reading outcomes in this population; the most effective type of intervention; and the contributions of instructional method to reading comprehension after decoding has been removed. These questions were answered with the help of 29 students from a rural school division in Saskatchewan who volunteered to participate in testing and various forms of reading intervention for a period of four to five weeks. Students were placed into one of three groups: the MSI group practiced decoding and learned six comprehension strategies; the FSI group practiced decoding and learned just two comprehension strategies; and the control group who participated in their typical education program. In sum, the analysis produced the following results:<p> 1.Pull-out intervention (pre-test M = 6.00; post-test M = 7.33) did not offer a statistically significant advantage over the typical classroom setting (pre-test M = 7.00; post-test M = 7.05) when attempting to remediate reading comprehension;<p> 2.Participants in the MSI group demonstrated significant improvement on measures of decoding (p = .001; ©¯p2 = .75);<p> 3.Although statistical testing did not reveal significant results, effect sizes were large for: participants in the MSI group on measures of fluency (©¯p2 = .39); participants in the FSI group on measures of fluency (©¯p2 = .53) and the Oral Reading Quotient (©¯p2 = .37); participants in the control group on measures of decoding (©¯p2 = .21), comprehension (©¯p2 = .38), fluency (©¯p2 = .32), and the Oral Reading Quotient (©¯p2 = .50); and<p> 4.Decoding accounted for a statistically significant 15.4% of the unique variance in post-test comprehension scores (p = .03), but differences in grouping contributed a negligible amount (p = .1; R2 change = .004).

Power line communications (PLC) surfers performance degradation due mainly to impulsive noise interference generated by electrical appliances. This thesis studies coded modulation techniques to improve the spectral efficiency and error performance of PLC. Considered in the first part is the application of bit-interleaved coded modulation with iterative decoding (BICM-ID) in class-A impulsive noise environment. In particular, the optimal soft-output demodulator and its suboptimal version are presented for an additive class-A noise (AWAN) channel so that iterative demodulation and decoding can be performed at the receiver. The effect of signal mapping on the error performance of BICM-ID systems in impulsive noise is then investigated, with both computer simulations and a tight error bound on the asymptotic performance. Extrinsic information transfer (EXIT) chart analysis is performed to illustrate the convergence properties of different mappings. The superior performance of BICMID compared to orthogonal frequency-division multiplexing (OFDM) is also clearly demonstrated.<p>Motivated by the successes of both BICM-ID and OFDM in improving the error performance of communications systems in impulsive noise environment, the second part of this thesis introduces a novel scheme of bit-interleaved coded OFDM with iterative decoding (BI-COFDM-ID) over the class-A impulsive noise channel. Here, an iterative receiver composed of outer and inner iteration loops is first described in detail. Error performance improvements of the proposed iterative receiver with different iteration strategies are presented and discussed. Performance comparisons of BI-COFDM-ID, BICM-ID and iteratively decoded OFDM are made to illustrate the superiority of BI-COFDM-ID. The effect of signal mapping on the error performance of BI-COFDM-ID is also studied.

One technique that is used to reduce the errors brought upon signals, when transmitted over noisy channels, is error control coding. One type of such coding, which has a good performance, is turbo coding. In some of the TMS320C64xTM digital signal processors there is a built in coprocessor that performs turbo decoding. This thesis is performed on the account of Communication Developments, within Saab AB and presents an evaluation of this coprocessor. The evaluation deals with both the memory consumption as well as the data rate. The result is also compared to an implementation of turbo coding that does not use the coprocessor. / En teknik som används för att minska de fel som en signal utsätts för vid transmission över en brusig kanal är felrättande kodning. Ett exempel på sådan kodning som ger ett mycket bra resultat är turbokodning. I några digitalsignalprocessorer, av sorten TMS320C64xTM, finns en inbyggd coprocessor som utför turboavkodning. Denna uppsats är utförd åt Communication Development inom Saab AB och presenterar en utvärdering av denna coprocessor. Utvärderingen avser såväl minnesförbrukning som datatakt och innehåller även en jämförelse med en implementering av turbokodning utan att använda coprocessorn.

Wireless communication is always struggling with errors in the transmission. The digital data received from the radio channel is often erroneous due to thermal noise and fading. The error rate can be lowered by using higher transmission power or by using an effective error correcting code. Power consumption and limits for electromagnetic radiation are two of the main problems with handheld devices today and an efficient error correcting code will lower the transmission power and therefore also the power consumption of the device. Duo-binary CTC is an improvement of the innovative turbo codes presented in 1996 by Berrou and Glavieux and is in use in many of today's standards for radio communication i.e. IEEE 802.16 (WiMAX) and DVB-RSC. This report describes the development of a duo-binary CTC decoder and the different problems that were encountered during the process. These problems include different design issues and algorithm choices during the design. An implementation in VHDL has been written for Alteras Stratix II S90 FPGA and a reference-model has been made in Matlab. The model has been used to simulate bit error rates for different implementation alternatives and as bit-true reference for the hardware verification. The final result is a duo-binary CTC decoder compatible with Alteras Stratix II designs and a reference model that can be used when simulating the decoder alone or the whole signal processing chain. Some of the features of the hardware are that block sizes, puncture rates and number of iterations are dynamically configured between each block Before synthesis it is possible to choose how many decoders that will work in parallel and how many bits the soft input will be represented in. The circuit has been run in 100 MHz in the lab and that gives a throughput around 50Mbit with four decoders working in parallel. This report describes the implementation, including its development, background and future possibilities.