9 research outputs found

    Multi-user video streaming using unequal error protection network coding in wireless networks

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    In this paper, we investigate a multi-user video streaming system applying unequal error protection (UEP) network coding (NC) for simultaneous real-time exchange of scalable video streams among multiple users. We focus on a simple wireless scenario where users exchange encoded data packets over a common central network node (e.g., a base station or an access point) that aims to capture the fundamental system behaviour. Our goal is to present analytical tools that provide both the decoding probability analysis and the expected delay guarantees for different importance layers of scalable video streams. Using the proposed tools, we offer a simple framework for design and analysis of UEP NC based multi-user video streaming systems and provide examples of system design for video conferencing scenario in broadband wireless cellular networks

    Optimized cross-layer forward error correction coding for H.264 AVC video transmission over wireless channels

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    Forward error correction (FEC) codes that can provide unequal error protection (UEP) have been used recently for video transmission over wireless channels. These video transmission schemes may also benefit from the use of FEC codes both at the application layer (AL) and the physical layer (PL). However, the interaction and optimal setup of UEP FEC codes at the AL and the PL have not been previously investigated. In this paper, we study the cross-layer design of FEC codes at both layers for H.264 video transmission over wireless channels. In our scheme, UEP Luby transform codes are employed at the AL and rate-compatible punctured convolutional codes at the PL. In the proposed scheme, video slices are first prioritized based on their contribution to video quality. Next, we investigate the four combinations of cross-layer FEC schemes at both layers and concurrently optimize their parameters to minimize the video distortion and maximize the peak signal-to-noise ratio. We evaluate the performance of these schemes on four test H.264 video streams and show the superiority of optimized cross-layer FEC design.Peer reviewedElectrical and Computer Engineerin

    Error resilient stereoscopic video streaming using model-based fountain codes

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    Ankara : The Department of Electrical and Electronics Engineering and the Institute of Engineering and Science of Bilkent University, 2009.Thesis (Ph.D.) -- Bilkent University, 2009.Includes bibliographical references leaves 101-110.Error resilient digital video streaming has been a challenging problem since the introduction and deployment of early packet switched networks. One of the most recent advances in video coding is observed on multi-view video coding which suggests methods for the compression of correlated multiple image sequences. The existing multi-view compression techniques increase the loss sensitivity and necessitate the use of efficient loss recovery schemes. Forward Error Correction (FEC) is an efficient, powerful and practical tool for the recovery of lost data. A novel class of FEC codes is Fountain codes which are suitable to be used with recent video codecs, such as H.264/AVC, and LT and Raptor codes are practical examples of this class. Although there are many studies on monoscopic video, transmission of multi-view video through lossy channels with FEC have not been explored yet. Aiming at this deficiency, an H.264-based multi-view video codec and a model-based Fountain code are combined to generate an effi- cient error resilient stereoscopic streaming system. Three layers of stereoscopic video with unequal importance are defined in order to exploit the benefits of Unequal Error Protection (UEP) with FEC. Simply, these layers correspond to intra frames of left view, predicted frames of left view and predicted frames of right view. The Rate-Distortion (RD) characteristics of these dependent layers are de- fined by extending the RD characteristics of monoscopic video. The parameters of the models are obtained with curve fitting using the RD samples of the video, and satisfactory results are achieved where the average difference between the analytical models and RD samples is between 1.00% and 9.19%. An heuristic analytical model of the performance of Raptor codes is used to obtain the residual number of lost packets for given channel bit rate, loss rate, and protection rate. This residual number is multiplied with the estimated average distortion of the loss of a single Network Abstraction Layer (NAL) unit to obtain the total transmission distortion. All these models are combined to minimize the end-toend distortion and obtain optimal encoder bit rates and UEP rates. When the proposed system is used, the simulation results demonstrate up to 2dB increase in quality compared to equal error protection and only left view error protection. Furthermore, Fountain codes are analyzed in the finite length region, and iterative performance models are derived without any assumptions or asymptotical approximations. The performance model of the belief-propagation (BP) decoder approximates either the behavior of a single simulation results or their average depending on the parameters of the LT code. The performance model of the maximum likelihood decoder approximates the average of simulation results more accurately compared to the model of the BP decoder. Raptor codes are modeled heuristically based on the exponential decay observed on the simulation results, and the model parameters are obtained by line of best fit. The analytical models of systematic and non-systematic Raptor codes accurately approximate the experimental average performance.Tan, A SerdarPh.D

    Enhanced Rateless Coding and Compressive Sensing for Efficient Data/multimedia Transmission and Storage in Ad-hoc and Sensor Networks

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    In this dissertation, we investigate the theory and applications of the novel class of FEC codes called rateless or fountain codes in video transmission and wireless sensor networks (WSN). First, we investigate the rateless codes in intermediate region where the number of received encoded symbols is less that minimum required for full datablock decoding. We devise techniques to improve the input symbol recovery rate when the erasure rate is unknown, and also for the case where an estimate of the channel erasure rate is available. Further, we design unequal error protection (UEP) rateless codes for distributed data collection of data blocks of unequal lengths, where two encoders send their rateless coded output symbols to a destination through a common relay. We design such distributed rateless codes, and jointly optimize rateless coding parameters at each nodes and relaying parameters. Moreover, we investigate the performance of rateless codes with finite block length in the presence of feedback channel. We propose a smart feedback generation technique that greatly improves the performance of rateless codes when data block is finite. Moreover, we investigate the applications of UEP-rateless codes in video transmission systems. Next, we study the optimal cross-layer design of a video transmission system with rateless coding at application layer and fixed-rate coding (RCPC coding) at physical layer. Finally, we review the emerging compressive sensing (CS) techniques that have close connections to FEC coding theory, and designed an efficient data storage algorithm for WSNs employing CS referred to by CStorage. First, we propose to employ probabilistic broadcasting (PB) to form one CS measurement at each node and design CStorage- P. Later, we can query any arbitrary small subset of nodes and recover all sensors reading. Next, we design a novel parameterless and more efficient data dissemination algorithm that uses two-hop neighbor information referred to alternating branches (AB).We replace PB with AB and design CStorage-B, which results in a lower number of transmissions compared to CStorage-P.Electrical Engineerin

    ๋ฌด์„  ํ†ต์‹  ๋„คํŠธ์›Œํฌ ํ™˜๊ฒฝ์—์„œ์˜ ํšจ๊ณผ์ ์ธ ๋น„๋””์˜ค ์ŠคํŠธ๋ฆฌ๋ฐ ๊ธฐ๋ฒ• ์—ฐ๊ตฌ

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    ํ•™์œ„๋…ผ๋ฌธ (๋ฐ•์‚ฌ)-- ์„œ์šธ๋Œ€ํ•™๊ต ๋Œ€ํ•™์› : ์ „๊ธฐ์ •๋ณด๊ณตํ•™๋ถ€, 2013. 8. ์ตœ์„ฑํ˜„.์˜ค๋Š˜๋‚  ๋ฌด์„  ๋„คํŠธ์›Œํฌ ํ†ต์‹  ๊ธฐ์ˆ ์˜ ๋ฐœ๋‹ฌ๋กœ ์ธํ•ด ๊ณ ํ’ˆ์งˆ์˜ ๋น„๋””์˜ค ์ŠคํŠธ๋ฆฌ๋ฐ ์„œ๋น„์Šค์— ๋Œ€ํ•œ ์š”๊ตฌ๊ฐ€ ๊ธ‰์ฆํ•˜๊ณ  ์žˆ๋‹ค. ์ƒˆ๋กœ์šด 60~GHz ๊ด‘๋Œ€์—ญ ๊ณ ์† ๋ฌด์„  ํ†ต์‹  ๊ธฐ์ˆ ์€ ๊ธฐ์กด์˜ ๋ฌด์„  ํ†ต์‹  ๊ธฐ์ˆ ์—์„œ๋Š” ๋ถˆ๊ฐ€๋Šฅํ–ˆ๋˜, ๊ณ ํ’ˆ์งˆ์˜ ๋ฌด์••์ถ• ๋น„๋””์˜ค ์ŠคํŠธ๋ฆฌ๋ฐ์„ ๊ฐ€๋Šฅํ•˜๊ฒŒ ํ•œ๋‹ค. ์ œํ•œ๋œ ๋ฌด์„  ์ž์› ํ™˜๊ฒฝ์—์„œ ๊ณ ํ’ˆ์งˆ์˜ ๋น„๋””์˜ค ์„œ๋น„์Šค๋ฅผ ์ง€์›ํ•˜๊ธฐ ์œ„ํ•ด ์ฃผ์–ด์ง„ ์ฑ„๋„ ํ™˜๊ฒฝ์—์„œ ์ ์ ˆํ•œ ๋ณ€์กฐ ๋ฐ ์ฝ”๋”ฉ ๊ธฐ์ˆ ์„ ์„ ํƒํ•˜๋Š” ํšจ์œจ์ ์ธ ๋งํฌ ์ ์‘ ๊ธฐ๋ฒ•์ด ํ•„์š”ํ•˜๋‹ค. ๋น„๋””์˜ค ์ŠคํŠธ๋ฆฌ๋ฐ์˜ ํ’ˆ์งˆ์„ ์ˆ˜์น˜๋กœ ํ‰๊ฐ€ํ•˜๋Š” ePSNR์„ ์ •์˜ํ•˜๊ณ , ๋ถˆํ‰๋“ฑ ์˜ค๋ฅ˜ ๋ณดํ˜ธ ๊ธฐ๋ฒ•(UEP)์„ ์ถ”๊ฐ€๋กœ ๋„์ž…ํ•˜์—ฌ ๋ณด๋‹ค ์„ธ๋ฐ€ํ•œ ๋งํฌ ์ ์‘ ๊ธฐ๋ฒ•์„ ๊ฐ€๋Šฅ์ผ€ ํ•œ๋‹ค. ์ •์˜ํ•œ ePSNR์„ ๊ธฐ๋ฐ˜์œผ๋กœ (1) ์ฃผ์–ด์ง„ ๋ฌด์„  ์ž์›์—์„œ ๋น„๋””์˜ค ํ’ˆ์งˆ์„ ์ตœ๋Œ€ํ™”, ํ˜น์€ (2) ๋ชฉํ‘œ ๋น„๋””์˜ค ํ’ˆ์งˆ์„ ๋งŒ์กฑํ•˜๋Š” ๋ฌด์„  ์ž์› ์‚ฌ์šฉ์„ ์ตœ์†Œํ™”, ํ•˜๋Š” ๋‘๊ฐ€์ง€ ๋งํฌ ์ ์‘ ๊ธฐ๋ฒ•๋“ค์„ ์ œ์•ˆํ•œ๋‹ค. ๋‹ค์–‘ํ•œ ์‹œ๋ฎฌ๋ ˆ์ด์…˜ ๊ฒฐ๊ณผ๋ฅผ ํ†ตํ•ด, ์ •์˜ํ•œ ePSNR์ด ๋น„๋””์˜ค ํ’ˆ์งˆ์„ ์ž˜ ํ‘œํ˜„ํ•˜๊ณ  ์žˆ์Œ์„ ํ™•์ธํ•˜์˜€๋‹ค. ๋˜ํ•œ, ์ œ์•ˆํ•œ ๋งํฌ ์ ์‘ ๊ธฐ๋ฒ•๋“ค์ด ๋น„๋””์˜ค ์ŠคํŠธ๋ฆฌ๋ฐ ์„œ๋น„์Šค๋ฅผ ์œ„ํ•œ ์ ์ ˆํ•œ ํ’ˆ์งˆ์„ ์ œ๊ณตํ•˜๋ฉด์„œ, ๋™์‹œ์— ์ž์› ํšจ์œจ์„ฑ์„ ํ–ฅ์ƒ์‹œํ‚ด์„ ๊ฒ€์ฆํ•˜์˜€๋‹ค. ํ•œํŽธ, ์ˆœ๋ฐฉํ–ฅ ์˜ค๋ฅ˜ ์ •์ • ๊ธฐ๋ฒ•(FEC)์€ ๋ฌด์„ ๋žœ ํ™˜๊ฒฝ์—์„œ ๊ณ ํ’ˆ์งˆ์˜ ์‹ ๋ขฐ์„ฑ์žˆ๋Š” ๋น„๋””์˜ค ๋ฉ€ํ‹ฐ์บ์ŠคํŠธ๋ฅผ ์ง€์›ํ•œ๋‹ค. ๋ฌด์„ ๋žœ ํ™˜๊ฒฝ์—์„œ ๋ณต์ˆ˜๊ฐœ์˜ ์•ก์„ธ์Šคํฌ์ธํŠธ(AP)๊ฐ„์˜ ์กฐ์ •์„ ํ†ตํ•œ ์‹ ๋ขฐ์„ฑ์žˆ๋Š” ๋น„๋””์˜ค ๋ฉ€ํ‹ฐ์บ์ŠคํŠธ ๊ธฐ๋ฒ•์„ ์ œ์‹œํ•œ๋‹ค. ๋ณต์ˆ˜๊ฐœ์˜ AP๊ฐ„์˜ ์กฐ์ •์„ ํ†ตํ•ด ๊ฐ๊ฐ์˜ AP๋“ค์ด (1) ์™„์ „ํžˆ ์„œ๋กœ ๋‹ค๋ฅธ, ํ˜น์€ (2) ๋ถ€๋ถ„์ ์œผ๋กœ ์„œ๋กœ ๋‹ค๋ฅธ, ์ธ์ฝ”๋”ฉ๋œ ํŒจํ‚ท๋“ค์„ ์ „์†กํ•˜๊ฒŒ ํ•˜์—ฌ, ๊ณต๊ฐ„ ๋ฐ ์‹œ๊ฐ„์  ๋‹ค์–‘์„ฑ์„ ๋ฉ€ํ‹ฐ์บ์ŠคํŠธ ์œ ์ €์—๊ฒŒ ์ œ๊ณตํ•  ์ˆ˜ ์žˆ๋‹ค. ์ถ”๊ฐ€๋กœ, ์ œํ•œ๋œ ๋ฌด์„  ์ž์›์„ ๋ณด๋‹ค ํšจ์œจ์ ์œผ๋กœ ์‚ฌ์šฉํ•˜๊ธฐ ์œ„ํ•ด, ์ˆœ๋ฐฉํ–ฅ ์˜ค๋ฅ˜ ์ •์ • ๊ธฐ๋ฒ•์˜ ์ฝ”๋”ฉ ๋น„์œจ ์ ์‘ ๊ธฐ๋ฒ•์„ ์œ„ํ•œ ์ž์› ํ• ๋‹น ์•Œ๊ณ ๋ฆฌ์ฆ˜์„ ์ œ์•ˆํ•œ๋‹ค. ๋˜ํ•œ, FEC ๋””์ฝ”๋”ฉ ํ›„์˜ ๋น„๋””์˜ค ํŒจํ‚ท์˜ ์ „์†ก์œจ๋ฅผ ์˜ˆ์ธกํ•  ์ˆ˜ ์žˆ๋Š” ๋ฐฉ๋ฒ•์„ ์ œ์•ˆํ•œ๋‹ค. ๋‹ค์–‘ํ•œ ์‹œ๋ฎฌ๋ ˆ์ด์…˜๊ณผ ์‹คํ—˜์„ ํ†ตํ•ด ์ œ์•ˆํ•œ ๊ธฐ๋ฒ•๋“ค์˜ ์šฐ์ˆ˜์„ฑ์„ ํ™•์ธํ•˜์˜€๋‹ค. ๋ฉ€ํ‹ฐ์บ์ŠคํŠธ ์ „์†ก์€ ๊ธฐ๋ณธ์ ์œผ๋กœ ๋ฌด์„  ์ฑ„๋„ ์˜ค๋ฅ˜๋กœ ์ธํ•ด ์ „์†ก ์‹คํŒจ๊ฐ€ ๋ฐœ์ƒํ•  ๊ฐ€๋Šฅ์„ฑ์„ ๋‚ดํฌํ•œ๋‹ค. ๊ทธ๋Ÿฌ๋‚˜ ๊ธฐ์กด์˜ ๋ฌด์„ ๋žœ ํ‘œ์ค€์—์„œ๋Š” ๋ฉ€ํ‹ฐ์บ์ŠคํŠธ ํ™˜๊ฒฝ์—์„œ ์ž๋™ ๋ฐ˜๋ณต ์š”์ฒญ ๊ธฐ๋ฒ•(ARQ)์„ ํ†ตํ•œ ์†์‹ค ์กฐ์ • ๋ฐฉ๋ฒ•์„ ์ œ๊ณตํ•˜์ง€ ์•Š์•˜๋‹ค. ๋ฉ€ํ‹ฐ์บ์ŠคํŠธ ์ „์†ก์˜ ๋น„์‹ ๋ขฐ์„ฑ ๋ฌธ์ œ๋ฅผ ํ•ด๊ฒฐํ•˜๊ธฐ ์œ„ํ•ด, ์ž๋™ ๋ฐ˜๋ณต ์š”์ฒญ ๊ธฐ๋ฒ•(ARQ)๊ณผ ์ˆœ๋ฐฉํ–ฅ ์˜ค๋ฅ˜ ์ •์ • ๊ธฐ๋ฒ•(FEC)๋ฅผ ํ•จ๊ป˜ ๊ณ ๋ คํ•œ ์‹ ๋ขฐ์„ฑ ์žˆ๋Š” ๋ฉ€ํ‹ฐ์บ์ŠคํŠธ ์ „์†ก ๊ธฐ๋ฒ•์„ ์ œ์•ˆํ•œ๋‹ค. ์‹ ๋ขฐ์„ฑ ์žˆ๋Š” ๋ฉ€ํ‹ฐ์บ์ŠคํŠธ ์ „์†ก์„ ์œ„ํ•œ ํ”ผ๋“œ๋ฐฑ ๊ตํ™˜์˜ ์˜ค๋ฒ„ํ—ค๋“œ๋ฅผ ์ค„์ด๊ธฐ ์œ„ํ•œ ๋ณต์ˆ˜๊ฐœ์˜ ํšจ์œจ์ ์ธ ํ”ผ๋“œ๋ฐฑ ๊ธฐ๋ฒ•์„ ์ œ์‹œํ•œ๋‹ค. ์ œ์•ˆํ•œ ํ”ผ๋“œ๋ฐฑ ๊ธฐ๋ฒ•์€ ์•ก์„ธ์Šคํฌ์ธํŠธ(AP)๊ฐ€ ๋ฉ€ํ‹ฐ์บ์ŠคํŠธ ์œ ์ €๋“ค์˜ ์†์‹ค๋œ ํŒจํ‚ท๋“ค์˜ ๋ณต์›์„ ์œ„ํ•ด ํ•„์š”ํ•œ ํŒจ๋ฆฌํ‹ฐ(parity) ํŒจํ‚ท์˜ ๊ฐœ์ˆ˜๋ฅผ ์‰ฝ๊ฒŒ ์•Œ ์ˆ˜ ์žˆ๋„๋ก ํ•œ๋‹ค. ํ”ผ๋“œ๋ฐฑ ๊ฐ„์˜ ์ถฉ๋Œ์„ ๊ฐ์•ˆํ•œ ์˜๋„์ ์ธ ๋™์‹œ ์ „์†ก์„ ํ†ตํ•ด ํ”ผ๋“œ๋ฐฑ ์˜ค๋ฒ„ํ—ค๋“œ๋ฅผ ๊ฐ์†Œ์‹œํ‚ฌ ์ˆ˜ ์žˆ๋‹ค. ์ถ”๊ฐ€๋กœ, ํšจ์œจ์ ์ธ ํ”ผ๋“œ๋ฐฑ ํ”„๋กœํ† ์ฝœ์„ ํ™œ์šฉํ•˜์—ฌ, ๋ณ€์กฐ ๋ฐ ์ฝ”๋”ฉ ๊ธฐ๋ฒ•(MCS)์˜ ํ์‡„์  ํ”ผ๋“œ๋ฐฑ ๊ธฐ๋ฐ˜์˜ ๋ฌผ๋ฆฌ ์ „์†ก ์†๋„ ์ ์‘ ๊ธฐ๋ฒ•์„ ์ œ์•ˆํ•œ๋‹ค. ์„ฑ๋Šฅ ๊ฒ€์ฆ์„ ํ†ตํ•ด ์ œ์•ˆํ•œ ๊ธฐ๋ฒ•๋“ค์ด ํšจ์œจ์ ์œผ๋กœ ํ”ผ๋“œ๋ฐฑ ์˜ค๋ฒ„ํ—ค๋“œ๋ฅผ ๊ฐ์†Œ์‹œํ‚ค๋ฉฐ, ๋™์‹œ์— ์‹ ๋ขฐ์„ฑ์žˆ๋Š” ๋ฉ€ํ‹ฐ์บ์ŠคํŠธ ์ „์†ก์„ ๋ณด์žฅํ•จ์„ ๊ฒ€์ฆํ•˜์˜€๋‹ค.Today, along with the rapid growth of the network performance, the demand for high-quality video streaming services has greatly increased. The emerging 60 GHz multi-Gbps wireless technology enables the streaming of high-quality uncompressed video, which was not possible with other existing wireless technologies. To support such high quality video with limited wireless resources, an efficient link adaptation policy, which selects the proper Modulation and Coding Scheme (MCS) for a given channel environment, is essential. We introduce a new metric, called expected Peak Signal-to-Noise Ratio (ePSNR), to numerically estimate the video streaming quality, and additionally adopt Unequal Error Protection (UEP) schemes that enable flexible link adaptation. Using the ePSNR as a criterion, we propose two link adaptation policies with different objectives. The proposed link adaptation policies attempt to (1) maximize the video quality for given wireless resources, or (2) minimize the required wireless resources while meeting the video quality. Our extensive simulation results demonstrate that the introduced variable, i.e., ePSNR, well represents the level of video quality. It is also shown that the proposed link adaptation policies can enhance the resource efficiency while achieving acceptable quality of the video streaming. Meanwhile, Forward Error Correction (FEC) can be exploited to realize reliable video multicast over Wi-Fi with high video quality. We propose reliable video multicast over Wi-Fi networks with coordinated multiple Access Points (APs) to enhance video quality. By coordinating multiple APs, each AP can transmit (1) entirely different or (2) partially different FEC-encoded packets so that a multicast receiver can benefit from both spatial and time diversities. The proposed scheme can enlarge the satisfactory video multicast region by exploiting the multi-AP diversity, thus serving more multicast receivers located at cell edge with satisfactory video quality. We propose a resource-allocation algorithm for FEC code rate adaptation, utilizing the limited wireless resource more efficiently while enhancing video quality. We also introduce the method for estimating the video packet delivery ratio after FEC decoding. The effectiveness of the proposed schemes is evaluated via extensive simulation and experimentation. The proposed schemes are observed to enhance the ratio of satisfied users by up to 37.1% compared with the conventional single AP multicast scheme. The multicast transmission is inherently unreliable due to the transmission failures caused by wireless channel errors, however, the error control with Automatic Repeat reQuest (ARQ) is not provided for the multicast transmission in legacy IEEE 802.11 standard. To overcome the unreliability of multicast transmission, finally, we propose the reliable multicast protocols considering both ARQ and packet-level FEC together. For the proposed reliable multicast protocol, to reduce the overheads of feedback messages while providing the reliable multicast service, the multiple efficient feedback protocols, i.e., Idle-time-based feedback, Slot-based feedback, Flash-based feedback, and Busy-time-based feedback, are proposed. The proposed feedback protocols let the AP know easily the number of requiring parity frames of the worst user(s) for the recovery of the lost packets. The feedback overheads can be reduced by intending the concurrent transmissions, which makes the collisions, between feedback messages. In addition, utilizing the efficient feedback protocols, we propose the PHY rate adaptation based on the close-loop MCS feedback in multicast transmissions. From the performance evaluations, the proposed protocols can efficiently reduce the feedback overheads, while the reliable multicast transmissions are guaranteed.1 Introduction 1 1.1 Video Streaming over Wireless Networks 1 1.1.1 Uncompressed Video Streaming over 60 GHz band 2 1.1.2 Video Multicast over IEEE 802.11 WLAN 3 1.2 Overview of Existing Approaches 5 1.2.1 Link Adaptation over Wireless Networks 5 1.2.2 Video Streaming over IEEE 802.11 WLAN 6 1.2.3 Reliable Multicast over IEEE 802.11 WLAN 8 1.3 Main Contributions 9 1.4 Organization of the Dissertation 11 2 Link Adaptation for High-Quality Uncompressed Video Streaming in 60 GHz Wireless Networks 12 2.1 Introduction 12 2.2 ECMA-387 and Wireless HDMI 17 2.2.1 ECMA-387 18 2.2.2 Wireless HDMI (HDMI PAL) 21 2.2.3 UEP Operations 22 2.2.4 ACK Transmissions for Video Streaming 23 2.2.5 Latency of Compressed and Uncompressed Video Streaming 24 2.3 ePSNR-Based Link Adaptation Policies 25 2.3.1 ePSNR 28 2.3.2 PSNR-based Link Adaptation 30 2.4 Performance Evaluation 33 2.4.1 Evaluation of ePSNR 34 2.4.2 Performance of Link Adaptation 40 2.5 Summary 45 3 Reliable Video Multicast over Wi-Fi Networks with Coordinated Multiple APs 47 3.1 Introduction 47 3.2 System Environments 50 3.2.1 Time-Slotted Multicast 50 3.2.2 FEC Coding Schemes 52 3.3 Reliable Video Multicast with Coordinated Multiple APs 52 3.3.1 Proposed Video Multicast 52 3.3.2 Video Multicast Procedure 55 3.4 FEC Code Rate Adaptation 58 3.4.1 Estimation of Delivery Ratio 59 3.4.2 Greedy FEC Code Rate Adaptation 61 3.5 Performance Evaluation 63 3.5.1 Raptor Code Performance 64 3.5.2 Simulation Results: No Fading 66 3.5.3 Simulation Results: Fading Channel 69 3.5.4 Simulation Results: Code Rate Adaptation 70 3.5.5 Experimental Results 74 3.5.6 Prototype Implementation 76 3.6 Summary 79 4 Reliable Video Multicast with Efficient Feedback over Wi-Fi 81 4.1 Introduction 81 4.2 Motivation 85 4.3 Proposed Feedback Protocols for Reliable Multicast 87 4.3.1 Idle-time-based Feedback 88 4.3.2 Slot-based Feedback 89 4.3.3 Flash-based Feedback 91 4.3.4 Busy-time-based Feedback 92 4.4 PHY Rate Adaptation in Multicast Transmission 93 4.5 Performance Evaluation 96 4.5.1 Performance evaluation considering feedback error 104 4.6 Summary 109 5 Conclusion and Future Work 110 5.1 Research Contributions 110 5.2 Future Research Directions 111 Abstract (In Korean) 121Docto

    Adaptive relaying protocol multiple-input multiple-output orthogonal frequency division multiplexing systems

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    In wireless broadband communications, orthogonal frequency division multiplexing (OFDM) has been adopted as a promising technique to mitigate multi-path fading and provide high spectral efficiency. In addition, cooperative communication can explore spatial diversity where several users or nodes share their resources and cooperate through distributed transmission. The concatenation of the OFDM technique with relaying systems can enhance the overall performance in terms of spectral efficiency and improve robustness against the detrimental effects of fading. Hybrid relay selection is proposed to overcome the drawbacks of conventional forwarding schemes. However, exciting hybrid relay protocols may suffer some limitations when used for transmission over frequency-selective channels. The combination of cooperative protocols with OFDM systems has been extensively utilized in current wireless networks, and have become a promising solution for future high data rate broadband communication systems including 3D video transmission. This thesis covers two areas of high data rate networks. In the first part, several techniques using cooperative OFDM systems are presented including relay selection, space time block codes, resource allocation and adaptive bit and power allocation to introduce diversity. Four (4) selective OFDM relaying schemes are studied over wireless networks; selective OFDM; selective OFDMA; selective block OFDM and selective unequal block OFDM. The closed-form expression of these schemes is derived. By exploiting the broadcast nature, it is demonstrated that spatial diversity can be improved. The upper bound of outage probability for the protocols is derived. A new strategy for hybrid relay selection is proposed to improve the system performance by removing the sub-carriers that experience deep fading. The per subcarrier basis selection is considered with respect to the predefined threshold signal-to-noise ratio. The closed-form expressions of the proposed protocol in terms of bit error probability and outage probability are derived and compared with conventional hybrid relay selection. Adaptive bit and power allocation is also discussed to improve the system performance. Distributed space frequency coding applied to hybrid relay selection to obtain full spatial and full data rate transmission is explored. Two strategies, single cluster and multiple clusters, are considered for the Alamouti code at the destination by using a hybrid relay protocol. The power allocation with and without sub-carrier pairing is also investigated to mitigate the effect of multipath error propagation in frequency-selective channels. The second part of this thesis investigates the application of cooperative OFDM systems to high data rate transmission. Recently, there has been growing attention paid to 3D video transmission over broadband wireless channels. Two strategies for relay selection hybrid relay selection and first best second best are proposed to implement unequal error protection in the physical layer over error prone channels. The closed-form expressions of bit error probability and outage probability for both strategies are examined. The peak signal-to-noise ratio is presented to show the quality of reconstruction of the left and right views

    Design of UEP-based MSE-minimizing rateless codes for source-channel coding

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    This paper proposes a method to optimize the performance of tandemsourceโ€“channel coding with respect to the mean-squared error by exploiting the unequal error protection coding. More specifically,we formulate a combination of linear programming and gridsearch to optimize degree distributions for unequal error protected rateless channel codes. An asymptotic upper bound for the meansquared error of the cascaded system is also derived. By optimizing the corresponding degree distributions of the rateless codes using unequal error protection principles, the proposed scheme has shown promising performance at high resolution region of sourcecoding.ยฉ 2011 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, 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 component of this work in other works. QC 2011112
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