Enhancing satellite system throughput using adaptive HARQ for delay tolerant services in mobile communications

In this paper we propose the introduction of adaptive hybrid automatic repeat request (HARQ) in the context of mobile satellite communications. HARQ schemes which are commonly used in terrestrial links, can be adapted to improve the throughput for delay tolerant services. The proposed method uses the estimation of the mutual information between the received and the sent symbols, in order to estimate the number of bits necessary to decode the message at next transmission. We evaluate the performance of our method by simulating a land mobile satellite (LMS) channel. We compare our results with the static HARQ scheme, showing that our adaptive retransmission technique has better efficiency while keeping an acceptable delay for services

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

Issued as final reportSamsung Advanced Institute of Technolog

Enhanced HARQ for Delay Tolerant Services in Mobile Satellite Communications

The objective of our paper is to improve efficiency (in terms of throughput or system capacity) for mobile satellite communications. In this context, we propose an enhanced Hybrid Automatic Repeat reQuest (HARQ) for delay tolerant services. Our proposal uses the estimation of the mutual information. We evaluate the performance of the proposed method for a land mobile satellite channel by means of simulations. Results are compared with those obtained with a classical incremental redundancy (IR) HARQ scheme. The technique we propose, shows a better performance in terms of efficiency while maintaining an acceptable delay for services

Bilayer Low-Density Parity-Check Codes for Decode-and-Forward in Relay Channels

This paper describes an efficient implementation of binning for the relay channel using low-density parity-check (LDPC) codes. We devise bilayer LDPC codes to approach the theoretically promised rate of the decode-and-forward relaying strategy by incorporating relay-generated information bits in specially designed bilayer graphical code structures. While conventional LDPC codes are sensitively tuned to operate efficiently at a certain channel parameter, the proposed bilayer LDPC codes are capable of working at two different channel parameters and two different rates: that at the relay and at the destination. To analyze the performance of bilayer LDPC codes, bilayer density evolution is devised as an extension of the standard density evolution algorithm. Based on bilayer density evolution, a design methodology is developed for the bilayer codes in which the degree distribution is iteratively improved using linear programming. Further, in order to approach the theoretical decode-and-forward rate for a wide range of channel parameters, this paper proposes two different forms bilayer codes, the bilayer-expurgated and bilayer-lengthened codes. It is demonstrated that a properly designed bilayer LDPC code can achieve an asymptotic infinite-length threshold within 0.24 dB gap to the Shannon limits of two different channels simultaneously for a wide range of channel parameters. By practical code construction, finite-length bilayer codes are shown to be able to approach within a 0.6 dB gap to the theoretical decode-and-forward rate of the relay channel at a block length of $10^5$ and a bit-error probability (BER) of $10^{-4}$. Finally, it is demonstrated that a generalized version of the proposed bilayer code construction is applicable to relay networks with multiple relays.Comment: Submitted to IEEE Trans. Info. Theor

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

Evaluation of Channel Coding Methods for Next Generation Mobile Communication Standards

La codificación de canales es crucial para los sistemas de comunicación móvil, y los sistemas de comunicación inalámbrica 5G han decidido utilizar los códigos LDPC como esquema de codificación para sus canales de datos y los códigos Polares como esquema de codificación para sus canales de control. Este estudio se centra en los fundamentos de los códigos LDPC y los códigos Polares, especialmente los nuevos códigos polares, explicando en detalle sus características de polarización y las técnicas de decodificación recursiva. También se estudia las especificaciones de diseño relacionadas con estos dos esquemas de codificación de canales en 5G. Mediante simulaciones, se compara el rendimiento del nuevo esquema de codificación de canales inalámbricos 5G con el de los códigos Turbo a diferentes longitudes de bloque y tasas de código, y se extraen conclusiones relevantes para demostrar la aplicabilidad del esquema de codificación de canales 5G NR.Channel coding is essential for mobile communication systems, and the 5G wireless standardization committees decided to use LDPC codes as the coding scheme of its data channel and Polar codes as the coding scheme of its control channel. This study focuses on the fundamentals of LDPC codes and Polar codes, especially the emerging Polar codes, with detailed explanations of their polarization characteristics and recursive decoding techniques. It is also focused on the design specification related to these two channel coding schemes in 5G. The performance of the 5G New Radio channel coding scheme is compared with that of LTE Turbo codes at different block lengths and code rates through simulations, and relevant conclusions are drawn to demonstrate the suitability of the 5G NR channel coding scheme.Grado en Ingeniería en Sistemas de Telecomunicació