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Grasshopper is an Android application which teaches users JavaScript through a series of coding puzzles. Grasshopper is able to make two types of real-time decisions based on the user's current performance: selecting an appropriate piece of feedback when the student is in the middle of solving a puzzle; and selecting the most appropriate next puzzle when the student is done with the current puzzle...
Fountain codes are used in many applications where the channels are time varying and it is difficult at the transmitter to predict the appropriate code rate. In this situation, fixedrate codes are not suitable. Despite the good performance of fountain codes, universally optimal codes do not exist in the finite-length regime. In this paper, we design new fountain codes that are robust to the communication...
On the one hand, Constraint Satisfaction Problems (CSP) are a declarative and expressive approach for modeling problems. On the other hand, propositional satisfiability problem (SAT) solvers can handle huge SAT instances up to millions of variables and clauses. In this article, we present an approach for taking advantage of both CSP modeling and SAT solving. Our technique consists in expressively...
On the one hand, Constraint Satisfaction Problems (CSP) are a declarative and expressive approach for modeling problems. On the other hand, propositional satisfiability problem (SAT) solvers can handle huge SAT instances up to millions of variables and clauses. In this article, we present an approach for taking advantage of both CSP modeling and SAT solving. Our technique consists in expressively...
Identifying tractable classes of constraint satisfaction problems (CSPs) has been studied over the past two decades, and is now a very active research domain. Recently, some works have shown the interest of these tractable classes from a different viewpoint. For example, it is known that if there is no broken triangle on each two values of a given variable in an arc-consistent binary CSP, then this...
Algebraic-geometric (AG) codes have long been considered as a possible candidate to replace Reed-Solomon (RS) codes. However, their decoding remains complex and infeasible to implement. Addressing this challenge, our paper proposes a low-complexity Chase (LCC) decoding algorithm for the most popular class of AG codes - Hermitian codes. The LCC decoding is realised by formulating decoding test-vectors,...
In this paper, we propose a method to improve H.265/HEVC encoding performance for 8K UHDTV moving pictures by detecting amount or complexity of object motions. In 8K video, which has high spatial resolution, motion has a big influence on encoding efficiency. The proposed method estimates motion complexity by external process, and selects an optimal prediction mode and search ranges of motion vectors...
Atypical sequences are subsequences of long sequences that deviate from the ‘normal’ data. In previous papers we have developed an information-theoretic approach to such sequences for discrete and real-valued data. In the current paper we extend the principle of real-valued data that follows vector Gaussian models, which allows for finding relationship between data. We include a simple application...
High Efficiency Video Coding (HEVC) is a novel video compression standard. It provides significantly better performance than its predecessor, but introduces high computational complexity due its hierarchical block structure. Determining Coding Units (CU), Prediction Units (PU), and Transform Units (TU) size is a time consuming process, as block partitioning decisions are based on rate-distortion optimization...
The High Efficiency Video Coding (HEVC) standard achieves higher encoding efficiency than previous standards such as H.264/AVC. One key contributor to this improvement is the intra-prediction method that supports a large number of prediction directions at a cost of high computational complexity. Within the context of mobile devices with limited power and computational capabilities, reductions on encoding...
Polar codes for channels with memory are considered in this paper. Şaşoğlu proved that Arikan's polarization applies to finite-state memory channels but practical decoding algorithms of polar codes for such channels have been unknown. This paper proposes a generalization of successive cancellation algorithm for channels with memory where the complexity is polynomial in the number of states. In addition,...
In network coding theory, when wiretapping attacks occur, secure network coding is introduced to prevent information from being leaked to adversaries. In practical network communications, secure constraints vary with time. How to effectively deal with information transmission and information security simultaneously under different security-levels is introduced in this paper as variable-security-level...
In this paper, we propose a new rateless code based on overlapped generations. This proposed scheme works very well especially in a broadcast scenario, where channels with different characteristics are involved in the system. In the proposed scheme, we allow the adjacent generations to overlap. Our main focus is on the design of rateless codes to make any receiver able to recover all the source file...
Coded multicasting has been shown to be a promising approach to significantly improve the caching performance of content delivery networks with multiple caches downstream of a common multicast link. However, achievable schemes proposed to date have been shown to achieve the proved order-optimal performance only in the asymptotic regime in which the number of packets per requested item goes to infinity...
In this paper, we propose a novel quantization parameter offset optimization scheme for screen content videos based on the high correlation among adjacent frames. Firstly, we define a measurement of inter-frame correlation for successive frames. Then, according to the defined correlation measurement, quantization parameter offset for different frames is appropriately adjusted. Experimental results...
During the summer of 2013, a group of high school Juniors from Newburgh Free Academy joined the program NetSci High (2013–2014) and had the opportunity to spend ten days at Boston University to learn more about network science. While there, the students learned about what networks are, how they are used, and why they are important. Consequently, they planned to combine a shared interest of literature...
The advent of the state-of-the-art video coding standard, High Efficiency Video Coding (HEVC) is expected to bring great changes to relevant fields of broadcasting, storage and communications. HEVC achieves higher coding gains compared to its previous video coding standards in terms of rate-distortion (R-D) performance with various improved coding tools. This leads to heavy computational complexity...
This paper considers that write-once memory (WOM) codes can be seen as a type of dirty-paper code. The current state of the memory, which is known to the encoder, plays the role of the known interference of dirty-paper coding. Erez, Shamai and Zamir showed that lattice strategies can achieve the capacity of the known-interference channel. In this paper, lattices are used to design a WOM code. Encoding...
A rate control algorithm for hierarchical B-pictures in Scalable Video Coding (SVC) is proposed in this work. The complex inter-frame dependency issue is effectively addressed by the Q-distance policy decision rule while the statistical smoothing effect enables the GOP-based precise bit rate control. The simplicity of the decision processes greatly reduces the encoder complexity providing an efficient...
Multiview video coding systems are characterized by their high encoding complexity. In this paper, we propose to reduce the encoding complexity by omitting frames at the encoder in a pattern that keeps the ability to reconstruct an interpolated version of each omitted frame, by motion-compensated and inter-view interpolation. Since our goal is maintaining good visual quality, we propose a method to...
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