Designing short-length Luby Transform (SLLT) codes to best protect video streaming and multicasting over lossy communication remains largely an empirical exercise. In this paper, we present a systematic approach to customize the decoding performance of these codes so that the protected video bitstreams may have the best playback quality over a wide range of channel loss rates. Our approach begins with the proposal of a new SLLT decoding performance model based on three parameters: decoding overhead, symbol decoding failure rate and tail probability of symbol decoding failure rate. We then formulate the design of SLLT codes as a multi-objective optimization problem, specify the design objectives in terms of goal program, and search for the most suitable codes using an augmented weighted Tchebycheff method implemented with the Covariance Matrix Adaptation Evolution Strategy (CMA-ES). Two design examples are provided to illustrate the effectiveness of our approach: (1) an SLLT post-code of a short-length raptor code that provides erasure protection to H.264 AVC bitstreams, and (2) an SLLT post-code of a rateless UEP code that supports graceful degradation of H.264 SVC playback quality. Empirical results demonstrate that the proposed method is capable of producing SLLT codes with customized decoding performance, whereas, the customized codes enable the playback pictures to attain significantly higher PSNR values at different stages of the decoding process than the pictures recovered under the protection of conventionally optimized codes.

An augmented brain computer interface that can detect users' brain states in real-life situations has been developed using wireless EEG headsets, smart phones and ubiquitous computing services. This kind of wearable natural user interfaces will have a wide-range of potential applications in future smart environments. This paper describes its ubiquitous system architecture and introduces its enabling technologies, which include machine-to-machine publish/subscribe protocols, multi-tier fog/cloud computing infrastructure and a linked data web. Its real-time responsiveness and easiness-of-use will be demonstrated by playing a multi-player on-line BCI game EEG Tractor Beam at the Intelligent Environment Conference.

The performance of LT code is highly related to the code length. A decoder is more likely to deplete degree-1 encoding symbols and terminate during early stage when the code length is short. In this work, we modify the robust Soliton distribution (RSD) and increase the degree-1 proportion. More degree-1 encoding symbols can be generated to relieve early decoding termination. The proportion of low degrees, except for degree-1, is also reduced. Therefore, receivers collect less encoding symbols carrying redundant information. In addition, Non-Repetitive (NR) encoding scheme is proposed to avoid producing repeated degree-1 encoding symbols. To improve video transmission quality, previous studies redesign LT codes to provide Unequal Error Protection (UEP) for different Scalable Video Coding (SVC) layers. Unlike those studies to modify the code structure, we integrate multiple NR encoders to achieve UEP ability. Experimental results show that our UEP scheme outperforms previous studies in terms of the PSNR.

Luby Transform (LT) and its companion Raptor codes are the most popular implementations of digital fountain codes. Performance of these rateless forward erasure correction codes is determined mainly by the degree distributions of their encoded symbols. Although the asymptotic behaviors of LT codes with large (>105) symbol blocks have been deduced analytically, a proficient method for finding the optimal degree distributions of short length (<103) LT codes is still absent. In this paper, we propose a practical approach to employ evolution strategies in finding the degree distributions of optimal short-length LT codes for different applications. Our approach begins with the development of a new performance model for LT codes based on three measurements: coding overhead ε, failure ratio r and failure occurrence probability p. Three evolution strategies (DE, CMA-ES and NES) were then employed to minimize these performance measurements separately with careful design of fitness functions and necessary transformations of decision variables. Throughout the evolution process, the performance of individual LT code in the population was evaluated with numerical simulations. Our experiments showed that the optimal degree distributions can be found using all three evolution strategies but with different convergence rates and the (r,p,ε) values of these optimized codes are all distributed on a smooth concave surface.

Wireless video streaming often suffers from heavy and varying amount of packet loss. Short-length Luby Transform (SLLT) codes are often employed to offer necessary rateless or universal erasure protection. Nevertheless, a proficient method for finding the optimal degree distributions of SLLT codes is still missing although the asymptotic behaviors of infinite-length LT codes have long been deduced. In this paper, we propose a practical approach to find the optimal degree distributions of LT codes with arbitrary input block lengths. Our approach starts with a new fitness model for the LT codes based on three performance measurements: their coding overhead ε, decoding failure ratio r and failure probability p. We then employed the exponential natural evolution strategy (xNES) along with a suitable choice of initial degree distribution and a proper transformation between the genotypes and the phenotypes to search for the optimized degree distributions. The optimized SLLT codes designed using this approach far outperforms the ones obtained through asymptotic approximation. As an example application, we constructed a family of rateless convolutional UEP codes using these optimized SLLT codes as the rateless postcodes. These codes offer superb universal unequal erasure protection to wireless H.264/SVC broadcasting with only 16%-20% coding overhead. This design exercise, however, made clear the necessity of matching the rateless erasure correction capability of the SLLT postcode with the error-rate sensitive UEP capability of the convolutional precode. The effect of code matching was demonstrated clearly in the improvement of rate-distortion performance of video playback.

Wireless broadcasting of scalable video coded medium grain scalable (SVC/MGS) bit streams requires unequal erasure protection (UEP) at the transport layer in order to ensure graceful degradation of playback video quality over a wide range of frame error rates. Modern wireless broadcasting systems even employ rate less fountain codes to aid the receivers in making inevitable tradeoffs among picture quality, channel throughput and playback latency. Designing a rate less UEP channel code fits for such an application posts distinct engineering challenges as the necessary protection for SVC base and enhancement layers differ by orders of magnitude while their intradependent groups of pictures fluctuate notably in their sizes. In this paper, we present the design and implementation of a rate less UEP convolutional code that meets these demanding requirements. Use of this UEP channel code along with rate-distortion based network application layer unit extraction offer sufficient protection to SVC bit streams under different lossy conditions without the need to re-code the bit stream. We also investigated the differences in playback performance of SVC bit streams that were protected by rate less codes vs. conventional Reed-Solomon codes. The comparison makes clear the advantages and the disadvantages of employing rate less codes in protecting wireless video broad-casting.

Luby Transform code (LT code) has been a popular and practical technique in the field of channel coding since its proposal. One of the key components of LT code is a degree distribution which is used to determine the relationship between source data and codewords. Luby in his proposal suggested two general methods to construct feasible degree distributions. Such general designs work appropriately in typical situations but not optimally in most cases. To explore the full potential of LT code, in this work, we make the first attempt to introduce evolutionary algorithms to optimize the degree distribution in LT code. Degree distributions are encoded as real-valued vectors and evaluated by numerical simulation of LT code. For applications of different natures, two objectives are implemented to search good degree distributions with different decoding behavior. Compared with the original design, the experimental results are quite promising and demonstrate that the degree distribution can be customized for different purposes. In addition to manually adjusting the degree distribution as the common practice, the work presented in this paper provides an efficient alternative approach to use and adapt LT code for both practitioners and researchers.

Luby Transform code (LT code) is the first practical digital fountain code and has been widely used as basic components in many communication applications. The coding behavior of LT code is mainly decided by a probability distribution of codeword degrees. In order to customize a degree distribution for different purposes, multi-objective evolutionary algorithm is introduced to optimize degree distributions in this paper. Two critical performance indicators of LT code are considered in our experiments. Some applications hope to minimize the overhead of extra packets and some require to limit the computational cost of the coding system. To handle this problem, MOEA/D is applied to optimize two objectives simultaneously. We expect to obtain the Pareto front (PF) formed by partial optimal solutions and provide those available degree distributions to different LT code applications. Not only promising results are represented in this paper but also the behavior of LT code is thoroughly explored by optimizing the degree distribution according to multi-objectives.