Thesis (M.S.) - U.S. Naval Postgraduate School, 1966. / Bibliography: leaf 41.

ITC/USA 2015 Conference Proceedings / The Fifty-First Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2015 / Bally's Hotel & Convention Center, Las Vegas, NV / The aeronautical telemeter channel is characterized by Multipath interference, Doppler shift and rapid changes in channel behavior. In addition to transmission error during aeronautical telemeter, transmission losing also exists. In this paper, we investigate the correction of transmission error and processing of telemetry transmission losing, and propose an adaptive coding scheme, which organic combines Fountain code and low density parity check (LDPC) code. We call it fountain LDPC (FLDPC) coding. In the coding scheme, The LDPC code is explored to perform transmission error correction, while, the problem of transmission losing is resorted to fountain code. So FLDPC is robust for transmission losing and transmission error. Moreover, without knowing any of these the channel information, FLDPC can adapt the data link and avoid the interference through adjusting the transmission rate. Experimental results illustrated that a signification improvement in transmission reliability and transmitting efficiency can be achieved by using the FLDPC coding.

No description available.

In wireless communication, multipath fading distorts the phase and the amplitude of received signals and increases error rate, which degrades causes communication quality. Multiple-input-multiple-output (MIMO) techniques can be adopted to achieve diversity gain and reduce error rate. However, MIMO is hard to be implemented in mobile devices due to size limitation. With this regard, cooperative communications are proposed to allow users to cooperate each other¡¦s and then achieve diversity without equipping multiple antennas. On the other hand, if source and relays adopt fixed-rate transmission under time-varying wireless channels, it requires timely feedback about channel-information for transmitters to adjust the rate of channel encoder. To reduce overhead required for aforementioned scheme, we adopt rateless fountain codes in cooperative networks. In recent year, most related studies focus on information-theoretical aspect, but it lacks discussion of practical coding. In our work, we use fountain codes in dual-hop cooperative communication and analyse transmission rate in terms of transmitting time. Fountain code was first proposed as Luby transform codes(LTC) for erasure channels. We combine low-density parity-check code( LDPC code) and LTC in cooperative communication networks, and analyze required transmission time under different cooperative protocols.

Network coding (NC) is an optimal data dissemination technique where intermediate nodes linearly combine incoming packets. To recover a network-coded message, a sink must use a Gaussian elimination decoder, but this high-complexity decoder may not be acceptable in resource-constrained applications like sensor networks. A good alternative to Gaussian elimination is for the sink to apply the well-known belief propagation (BP) algorithm; however, the performance and complexity of BP decoding is dependent on the statistics of the linearly-combined packets. In this work, we propose two protocols that address this issue by applying fountain coding paradigms to network codes. For a two-source, single-relay, and single-sink network, named the Y-network, if the relay can network-code incoming packets while maintaining the key properties of the fountain code, then BP decoding can be applied efficiently to recover the original message. Particularly, the sink should see a Soliton-like degree distribution for efficient BP decoding. The first protocol, named Soliton-like rateless coding (SLRC), recognizes that certain encoded packets are essential for BP decoding to perform well. Therefore, the relay protects these important packets by immediately forwarding them to the sink. It can be shown analytically that the proposed scheme is resilient to nodes leaving the transmission session. Through simulations, the SLRC scheme is shown to perform better than buffer-and-forwarding, and the Distributed LT code. Although SLRC achieves good performance, the degree distribution seen by the sink is non-optimal and assumes that a large number of packets can be buffered, which may not always be possible. Extending SLRC, we propose the Improved Soliton-like Rateless Coding (ISLRC) protocol. Assuming a resource-constrained relay, the available resources at the relay are effciently utilized by performing distribution shaping; packets are intelligently linearly combined. The aggregate degree distribution for the worst case is derived and used in performing an asymptotic error analysis using an AND-OR tree analysis. Simulation results show that even under the worst case scenario of ISLRC, better performance can be achieved compared to SLRC and other existing schemes. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2011-10-07 21:13:03.862

Thesis (M.S.)--University of Hawaii at Manoa, 2005. / Includes bibliographical references (leaves 56-61). / x, 61 leaves, bound ill. 29 cm

In the autumn of 2020, I was an intern at Fontänhuset Sköndal and there my curiosity was aroused to know more about the organization and the people in it. The purpose of my thesis was to investigate whether Fountain houses members' mental health has improved since they started participating in the activities, I wanted to investigate whether empowerment was the reason for the members possibly improved mental health. In this study, I interviewed four members and three employees / supervisors. My assumption that the well-being of the members of Fountain houses was positively affected was to some extent correct. All stated that they felt better since they started at Fontain Houses, but still they continued to medicate and have contact with the traditional psychiatric care. That empowerment in the form of joint work, participation, co-determination and autonomy was crucial in their perception of their mental health. Due to the current corona pandemic, the Fountain houses cannot be open as usual and members cannot participate in all the daily tasks.Hopefully the restrictions will soon end so that members can return to a structured existence with routines, join tasks and social company.Structure and routines are important for people with mental illness. The importance of Fountain houses is becoming more significant as mental illness spreads in the country. It is gratifying that several members are actively involved in establishing more Fountain houses in Sweden. / Hösten 2020 var jag praktikant på Fontänhuset Sköndal och där väcktes min nyfikenhet att veta mer om organisationen och människorna i den. Syftet med min uppsats var att undersöka om Fontänhusens medlemmars psykiska hälsa förbättrats sedan de började delta i verksamheten. Jag ville undersöka om empowerment var anledningen till medlemmarnas eventuellt förbättrade psykiska hälsa. I denna studie har jag intervjuat fyra medlemmar och tre anställda/handledare. Mitt antagande att Fontänhusens medlemmars mående påverkades positivt stämde till viss del. Samtliga uppgav att de mådde bättre sedan de började på Fontänhusen men likväl fortsatte de medicinera och ha kontakt med den traditionella psykiatriska vården. Att empowerment i form av gemensamt arbete, delaktighet, medbestämmande, egenmakt hade avgörande betydelse i deras uppfattning om sitt psykiska hälsotillstånd.  På grund av den rådande coronapandemin kan inte Fontänhusen ha öppet som vanligt och många av husens normala, dagliga arbetsuppgifter kan inte alla medlemmar delta i. Förhoppningen är att begränsningarna snarast upphör så att medlemmarna kan återgå till en strukturerad tillvaro med rutiner, gemensamma arbetsuppgifter och social samvaro. Struktur och rutiner är viktigt för människor med psykisk ohälsa. Fontänhusens betydelse får ökad aktualitet i och med att den psykiska ohälsan breder ut sig i landet. Det är glädjande att flera medlemmar aktivt engagerar sig för att fler Fontänhus ska etableras i Sverige.

This thesis investigates four FEC (forward error correction) coding schemes for their suitability for a broadcast system where there is one energy-rich transmitter and many energy-constrained receivers with a variety of channel conditions. The four coding schemes are: repetition codes (the baseline scheme); Reed-Solomon (RS) codes; Luby-Transform (LT) codes; and a type of RS and LT concatenated codes. The schemes were tested in terms of their ability to achieve both high average data reception success probability and short data reception time at the receivers (due to limited energy). The code rate (Rc) is fixed to either 1/2 or 1/3. Two statistical channel models were employed: the memoryless channel and the Gilbert-Elliott channel. The investigation considered only the data-link layer behaviour of the schemes. During the course of the investigation, an improvement to the original LT encoding process was made, the name LTAM (LT codes with Added Memory) was given to this improved coding method. LTAM codes reduce the overhead needed for decoding short-length messages. The improvement can be seen for decoding up to 10000 number of user packets. The maximum overhead reduction is as much as 10% over the original LT codes. The LT-type codes were found to have the property that can both achieve high success data reception performance and flexible switch off time for the receivers. They are also adaptable to different channel characteristics. Therefore it is a prototype of the ideal coding scheme that this project is looking for. This scheme was then further developed by applying an RS code as an inner code to further improve the success probability of packet reception. The results show that LT&RS code has a significant improvement in the channel error tolerance over that of the LT codes without an RS code applied. The trade-off is slightly more reception time needed and more decoding complexity. This LT&RS code is then determined to be the best scheme that fulfils the aim in the context of this project which is to find a coding scheme that both has a high overall data reception probability and short overall data reception time. Comparing the LT&RS code with the baseline repetition code, the improvement is in three aspects. Firstly, the LT&RS code can keep full success rate over channels have approximately two orders of magnitude more errors than the repetition code. This is for the two channel models and two code rates tested. Secondly, the LT&RS code shows an exceptionally good performance under burst error channels. It is able to maintain more than 70% success rate under the long burst error channels where both the repetition code and the RS code have almost zero success probability. Thirdly, while the success rates are improved, the data reception time, measured in terms of number of packets needed to be received at the receiver, of the LT&RS codes can reach a maximum of 58% reduction for Rc = 1=2 and 158% reduction for Rc = 1=3 compared with both the repetition code and the RS code at the worst channel error rate that the LT&RS code maintains almost 100% success probability.

Fountain codes were introduced to provide higher reliability, lower complexities, and more scalability for networks such as the Internet. In this thesis, we study Luby- Transform (LT) codes which are the realization of Fountain codes. In the LT codes, a sparse random factor graph is dynamically generated on both the encoder and decoder sides of the communications channel. The graph is generated from an ensemble degree distribution. The LT codes are also known as rateless codes, in the sense that they can generate potentially limitless codeword symbols from original data and self-adjust to channels with different erasure probabilities. LT Codes also have a very low encoding and decoding complexities when comparing with some traditional block codes, e.g., Reed Solomon (RS) codes and Low-Density-Parity-Check (LDPC) codes. Therefore, LT Codes are suitable for many different kinds of applications such as broadcast transmission. LT codes achieve the capacity of the Binary Erasure Channel (BEC) asymptotically and universally. For finite lengths, the search is continued to nd codes closer to the capacity limits at even lower encoding and decoding complexities. Most previous work on single-layer Fountain coding targets the design via the right degree distribution. The left degree distribution of an LT code is left as Poisson to protect the universality. For finite lengths, this is no longer an issue; thus, we focus on the design of better codes for the BEC and noisy channels as well at practical lengths. We propose two encoding schemes for BEC and noisy channels by shaping the left degree distribution. Our left degree shaping provides codes outperforming regular LT code and all other competing schemes in the literature. For instance, at a bit error rate of 10_{-7} and k = 256, our scheme provides a realized rate of 0.6 which is 23.5% higher than Sorensen et al.'s scheme over BEC. In addition, over noisy channels our proposed scheme achieves an improvement of 14% in the released rates at k = 100 and 30 Belief Propagation (BP) iterations. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2013-08-22 19:40:59.885

abstract: Blockchain scalability is one of the issues that concerns its current adopters. The current popular blockchains have initially been designed with imperfections that in- troduce fundamental bottlenecks which limit their ability to have a higher throughput and a lower latency. One of the major bottlenecks for existing blockchain technologies is fast block propagation. A faster block propagation enables a miner to reach a majority of the network within a time constraint and therefore leading to a lower orphan rate and better profitability. In order to attain a throughput that could compete with the current state of the art transaction processing, while also keeping the block intervals same as today, a 24.3 Gigabyte block will be required every 10 minutes with an average transaction size of 500 bytes, which translates to 48600000 transactions every 10 minutes or about 81000 transactions per second. In order to synchronize such large blocks faster across the network while maintain- ing consensus by keeping the orphan rate below 50%, the thesis proposes to aggregate partial block data from multiple nodes using digital fountain codes. The advantages of using a fountain code is that all connected peers can send part of data in an encoded form. When the receiving peer has enough data, it then decodes the information to reconstruct the block. Along with them sending only part information, the data can be relayed over UDP, instead of TCP, improving upon the speed of propagation in the current blockchains. Fountain codes applied in this research are Raptor codes, which allow construction of infinite decoding symbols. The research, when applied to blockchains, increases success rate of block delivery on decode failures. / Dissertation/Thesis / Masters Thesis Computer Science 2018