Network flow algorithms for wireless networks and design and analysis of rate compatible LDPC codes

While Shannon already characterized the capacity of point-to-point channels back in 1948, characterizing the capacity of wireless networks has been a challenging problem. The deterministic channel model proposed by Avestimehr, etc. (2007 - 1) has been a promising approach for approximating the Gaussian channel capacity and has been widely studied recently. Motivated by this model, an improved combinatorial algorithm is considered for finding the unicast capacity for wireless information flow on such deterministic networks in the first part of this thesis. Our algorithm fully explores the useful combinatorial features intrinsic in the problem. Our improvement applies generally with any size of finite fields associated with the channel model. Comparing with other related algorithms, our improved algorithm has very competitive performance in complexity. In the second part of our work, we consider the design and analysis of rate-compatible LDPC codes. Rate-compatible LDPC codes are basically a family of nested codes, operating at different code rates and all of them can be encoded and decoded using a single encoder and decoder pair. Those properties make rate-compatible LDPC codes a good choice for changing channel conditions, like in wireless communications. The previous work on the design and analysis of LDPC codes are all targeting at a specific code rate and no work is known on the design and analysis of rate-compatible LDPC codes so that the code performance at all code rates in the family is manageable and predictable. In our work, we proposed algorithms for the design and analysis of rate-compatible LDPC codes with good performance and make the code performance at all code rates manageable and predictable. Our work is based on E2RC codes, while our approaches in the design and analysis can be applied more generally not only to E2RC codes, but to other suitable scenarios, like the design of IRA codes. Most encouragingly, we obtain families of rate-compatible codes whose gaps to capacity are at most 0.3 dB across the range of rates when the maximum variable node degree is twenty, which is very promising compared with other existing results

Development of rate-compatible structured LDPC CODEC algorithms and hardware IP

Issued as final reportSamsung Advanced Institute of Technolog

Untainted Puncturing for Irregular Low-Density Parity-Check Codes

Puncturing is a well-known coding technique widely used for constructing rate-compatible codes. In this paper, we consider the problem of puncturing low-density parity-check codes and propose a new algorithm for intentional puncturing. The algorithm is based on the puncturing of untainted symbols, i.e. nodes with no punctured symbols within their neighboring set. It is shown that the algorithm proposed here performs better than previous proposals for a range of coding rates and short proportions of punctured symbols.Comment: 4 pages, 3 figure

Encoding Design and Simulation of Rate-Compatible Multi-Edge Type LDPC Codes

码率自适应编码技术是为了充分利用移动通信中的频谱资源而出现的，是有效进行无线传输的方法之一。采用码率自适应的编码技术，可以在不牺牲功率和比特错误率的前提下，更好的利用信道容量，并提高移动通信系统的频谱利用率。在无线通信系统中常常把码率自适应编码技术应用在混合自动重传（HybridAutomaticRepeatRequest，即HARQ）方案中来获得系统的高吞吐量。 本文介绍了一种新的码型，即多边型低密度奇偶校验码（Multi-EdgeTypeLowDensityParityCheckCodes，简称多边型LDPC码或MET－LDPC码）。与传统的LDPC码相比，MET-LDPC码作为一种更加...In order to make full use of spectrum resources for mobile communication,rate-compatible codes can be applied. Rate-compatible coding technology is an efficient wireless transmission method. It is often used to improve frequency efficiency of mobile communication system and make better use of channel capacity. In wireless communication systems, rate-compatible codes can be applied to the hybri...学位：工学硕士院系专业：信息科学与技术学院通信工程系_通信与信息系统学号：2332007115218

Efficient Information Reconciliation for Quantum Key Distribution = Reconciliación eficiente de información para la distribución cuántica de claves

Advances in modern cryptography for secret-key agreement are driving the development of new methods and techniques in key distillation. Most of these developments, focusing on information reconciliation and privacy amplification, are for the direct benefit of quantum key distribution (QKD). In this context, information reconciliation has historically been done using heavily interactive protocols, i.e. with a high number of channel communications, such as the well-known Cascade. In this work we show how modern coding techniques can improve the performance of these methods for information reconciliation in QKD. Here, we propose the use of low-density parity-check (LDPC) codes, since they are good both in efficiency and throughput. A price to pay, a priori, using LDPC codes is that good efficiency is only attained for very long codes and in a very narrow range of error rates. This forces to use several codes in cases when the error rate varies significantly in different uses of the channel, a common situation for instance in QKD. To overcome these problems, this study examines various techniques for adapting LDPC codes, thus reducing the number of codes needed to cover the target range of error rates. These techniques are also used to improve the average efficiency of short-length LDPC codes based on a feedback coding scheme. The importance of short codes lies in the fact that they can be used for high throughput hardware implementations. In a further advancement, a protocol is proposed that avoids the a priori error rate estimation required in other approaches. This blind protocol also brings interesting implications to the finite key analysis. Los avances en la criptografía moderna para el acuerdo de clave secreta están empujando el desarrollo de nuevos métodos y técnicas para la destilación de claves. La mayoría de estos desarrollos, centrados en la reconciliación de información y la amplificación de privacidad, proporcionan un beneficio directo para la distribución cuántica de claves (QKD). En este contexto, la reconciliación de información se ha realizado históricamente por medio de protocolos altamente interativos, es decir, con un alto número de comunicaciones, tal y como ocurre con el protocolo Cascade. En este trabajo mostramos cómo las técnicas de codificación modernas pueden mejorar el rendimiento de estos métodos para la reconciliación de información en QKD. Proponemos el uso de códigos low-density parity-check (LDPC), puesto que estos son buenos tanto en eficiencia como en tasa de corrección. Un precio a pagar, a priori, utilizando códigos LDPC es que una buena eficiencia sólo se alcanza para códigos muy largos y en un rango de error limitado. Este hecho nos obliga a utilizar varios códigos en aquellos casos en los que la tasa de error varía significativamente para distintos usos del canal, una situación común por ejemplo en QKD. Para superar estos problemas, en este trabajo analizamos varias técnicas para la adaptación de códigos LDPC, y así poder reducir el número de códigos necesarios para cubrir el rango de errores deseado. Estas técnicas son también utilizadas para mejorar la eficiencia promedio de códigos LDPC cortos en un esquema de codificación con retroalimentación o realimentación (mensaje de retorno). El interés de los códigos cortos reside en el vii hecho de que estos pueden ser utilizados para implementaciones hardware de alto rendimiento. En un avance posterior, proponemos un nuevo protocolo que evita la estimación inicial de la tasa de error, requerida en otras propuestas. Este protocolo ciego también nos brinda implicaciones interesantes en el análisis de clave finita

Topologically Driven Methods for Construction Of Multi-Edge Type (Multigraph with nodes puncturing) Quasi-Cyclic Low-density Parity-check Codes for Wireless Channel, WDM Long-Haul and Archival Holographic Memory

In this Phd thesis discusses modern methods for constructing MET QC-LDPC codes with a given error correction ("waterfall, error-floor") and complexity (parallelism level according circulant size plus scheduler orthogonality of checks) profiles: 1. weight enumerators optimization, protograph construction using Density Evolution, MI (P/Exit-chart) and it approximation: Gaussian Approximation, Reciprocal-channel approximation and etc; 2. Covariance evolution and it approximation; 3. Lifting methods for QC codes construction:PEG, Guest-and-Test, Hill-Climbing with girth, EMD, ACE optimization; 4. Upper and lower bounds on code distance estimation and its parallel implementation using CPU/GPU; 5. Brouwer-Zimmerman and Number Geometry code distance estimation methods; 6. Importance Sampling for error-floor estimation; 7. Length and rate adaption methods for QC codes based on cyclic group decomposition; 8. Methods for interaction screening which allow to improve performance (decorrelate variables) under BP and it's approximation. We proposed several state-of-the-art methods: Simulated Annealing lifting for MET QC-LDPC codes construction; fast EMD and code distance estimation; floor scale modular lifting for lenght adaption; fast finite-length covariance evolution rate penalty from threshold for code construction and it hardware friendly compression for fast decoder's LLRs unbiasing due SNR's estimation error. We found topology reason's of efficient of such methods using topology thickening (homotopy of continuous and discrete curvature) under matched metric space which allow to generalize this idea to a class of nonlinear codes for Signal Processing and Machine Learning. Using the proposed algorithms several generations of WDM Long-Haul error-correction codes were built. It was applied for "5G eMBB" 3GPP TS38.212 and other applications like Flash storage, Compressed sensing measurement matrix.Comment: Phd Thesis, 176 pages, in Russian, 62 pictures, 13 tables, 5 appendix including links to binary and source code

Inequitable by Design: The Patent Culture, Law, and Politics Behind COVID-19 Vaccine Global Access

COVID-19 vaccine access has been highly inequitable worldwide, with coverage depending largely on a country’s wealth. By the end of 2021, 64.1% of people living in high-income countries had received at least one dose of the vaccine, compared to only 5.4% of those in low-income countries. Similarly, only high- and upper-middle-income countries had received the most effective vaccines. The uneven distribution of these lifesaving vaccines is made complex due to the convergence of several factors, but it suggests that the extraordinary expanding and ossifying market and political power of a few vaccine manufacturers founded on intellectual property and complementary policies is a decisive factor in shaping our healthcare systems and securing equitable access to vaccines. This Article analyzes the power dynamics of vaccine manufacturing and distribution of U.S. pharmaceutical companies in the context of global COVID-19 vaccination. Drawing on the health-justice and law-and-political-economy scholarship of the last decade, this Article demonstrates how a “patent culture” shaped by intellectual property law fundamentally neglects health-equity principles while politicizing healthcare access. These contemporary frameworks suggest that the global COVID-19 vaccine-access problem is the result of avoidable policy choices made by big manufacturers and affluent governments. Despite a long history of inequities in access to healthcare, policy choices—as predicted by Hart’s inverse equity theory—have favored a purposely inequitable-by-design vaccination program driven by the wealth and power of those allowed to control vaccine production and supply globally. Finally, this Article proposes ways to challenge the normalized and institutionalized patent culture that has commodified access to lifesaving medicines beyond national borders. As it examines national and international legal strategies to address the vaccine-access problem, the Article suggests equity-based principles of public value, transparency, and inclusivity to guide healthcare governance and future reformation of the vaccine-access landscape. An interdisciplinary analysis of the first year of the global vaccine rollout provides an account critical to future policies aiming to address the structural conditions needed to attain equitable health outcomes, even after the pandemic

The application of pole mounted amorphous core transformers to the electrical distribution network.

Master of Science in Electrical Engineering. University of KwaZulu-Natal, Durban 2016.With the drive to save money when supplying electricity to customers, utilities are looking for solutions to decrease losses on distribution lines while maintaining good quality of supply. Amorphous core transformers are known for having the lower no-load losses compared to cold rolled grain orientated transformers and hence may be an important technology to decrease losses on the distribution network. The amorphous material is easily magnetised, however this comes at the expense of a lower saturation point and the transformer may need to be designed at a lower peak flux density. Inrush currents are a phenomenon that occurs when a transformer is switched on. The combination of the voltage switching angle and the remnant flux lead to an overflux and subsequent saturation of the core material, this leads to a high current. The purpose of this dissertation is to investigate the performance of amorphous core transformers installed on distribution lines, where they are switched onto the network from the high voltage side, and conclude if they are a suitable replacement for cold rolled grain oriented steel core. Inrush currents have been investigated through a circuit model developed in Alternative Transients Program/Electromagnetic Transients Program (ATP/EMTP) to determine the currents for various designs of transformers. The model consists of the non-linear component related to the core used as well as the air core of the high voltage winding. The circuit model has been validated through an experiment. A study was undertaken to understand the difference in the forces between amorphous core transformers and cold rolled grain orientated, this was investigated in Finite Element Method Magnetics (FEMM) by determining the distribution of magnetic flux. Additionally, as the inrush current is only seen on the high voltage winding and not the low voltage winding, the models were compared to the forces due to short-circuit currents, where there is current on both high voltage and low voltage windings and a different magnetic flux distribution. The position of the tap winding was of interest as it results in an unsymmetrical force distribution

Characterization of the ovine Major Histocompatibility Complex (MHC) class I genes

The ovine major histocompatibility complex (MHC) remains poorly characterized compared with those of other livestock species. To develop cellular and molecular tools to support development of vaccines against intracellular pathogens of sheep, a molecular genetic analysis of four distinct ovine MHC haplotypes carried by two heterozygous Blackface rams (501 and 504) was conducted. A total of 17 novel sequences was identified, 11 of which were obtained full length. Initially, using a combination of reverse transcriptase - polymerase chain reaction (RT-PCR), Single Stranded Conformational Polymorphism (SSCP) and sequence analysis, six distinct SSCP patterns were identified from ram 501 and eight from ram 504 each corresponding to a different sequence (chapter 3). SSCP patterns and their corresponding sequences D5, D3, C7, E2, F8 and F12 accounted for 86% of 360 clones analysed from both rams, suggesting that they encode the mainly expressed classical class I molecules, while F7 and G12 represented only 0.56%, indicating they are putative low expressed class I like genes or pseudogenes. Genotyping of 17 offspring from both rams using a novel sequence specific PCR method, allowed the segregation of sequences within the four haplotypes (chapter 4). An additional sequence C7b was identified during genotyping, indicating that at least 6 class I genes are transcribed in a single haplotype. F7 and G12 were shared between all four haplotypes. Full length transcripts for ten of the sequences identified in chapter 3 were obtained by RT-PCR, all having a characteristic MHC gene structure (chapter 5). During full length amplification two additional sequences, N1 and N2, were identified with characteristics consistent with non classical class I loci. Phylogenetic analysis using the identified transcripts and published ovine, bovine and other ruminant class I sequences belonging to the Bovidae family indicated that there are at least six ovine MHC class I loci (chapter 6). Sequences N1 and N2 are closer to the non classical bovine MHC class I sequence HD15 than to the remaining ovine class I transcripts. Seven out of eight full length transcripts subcloned into a mammalian expression vector expressed detectable class I cell surface glycoproteins in COS-7 cells (chapter 7). The combination of phylogenetic analysis, haplotype, transcription and expression data suggest that there are at least four distinct polymorphic ovine MHC class 1 loci, three of which appear to be expressed in a number of combinations in individual haplotypes, a couple of non polymorphic poorly transcribed class I like sequences and at least one additional diverged non classical class I locus (chapter 8). Similarities and differences of the ovine MHC class I region with that of other species are discussed. Using the data generated here, an MHC defined sheep flock, which includes animals homozygous for each of the four MHC haplotypes is currently under development. The MHC defined resource population, along with the transfected cell lines expressing each of the full length ovine MHC class I sequences, comprise tools for immunization and disease association experiments studying the protective immunity to intracellular pathogens of sheep