Showing papers by "Chao Tian published in 2013"

Rate Region of the (4,3,3) Exact-Repair Regenerating Codes

Abstract: Exact-repair regenerating codes are considered for the case (n,k,d)=(4,3,3), for which a complete characterization of the rate region is provided. This characterization answers in the affirmative the open question whether there exists a non-vanishing gap between the optimal bandwidth-storage tradeoff of the functional-repair regenerating codes (i.e., the cut-set bound) and that of the exact-repair regenerating codes. The converse proof relies on the existence of symmetric optimal solutions. For the achievability, only one non-trivial corner point of the rate region needs to be addressed, for which an explicit binary code construction is given.

Exact-repair regenerating codes via layered erasure correction and block designs

Abstract: A new class of exact-repair regenerating codes is constructed by combining two layers of erasure correction codes together with combinatorial block designs. The proposed codes have the “uncoded repair” property where the nodes participating in the repair simply transfer part of the stored data directly, without performing any computation. The layered error correction structure results in a low-complexity decoding process. An analysis of our coding scheme is presented. This construction is able to achieve better performance than timesharing between the minimum storage regenerating codes and the minimum repair-bandwidth regenerating codes.

Rate region of the (4, 3, 3) exact-repair regenerating codes

Abstract: Exact-repair regenerating codes are considered for the case (n, k, d) = (4, 3,3), for which a complete characterization of the rate region is provided. This characterization answers in the affirmative the open question whether there exists a non-vanishing gap between the optimal bandwidth-storage tradeoff of the functional-repair regenerating codes (i.e., the cut-set bound) and that of the exact-repair regenerating codes. The converse proof relies on the existence of symmetric optimal solutions. For the achievability, only one non-trivial corner point of the rate region needs to be addressed, for which an explicit binary code construction is given.

Capacity-Achieving Polar Codes for Arbitrarily Permuted Parallel Channels

Abstract: Channel coding over arbitrarily permuted parallel channels was first studied by Willems and coworkers. This paper introduces capacity-achieving polar coding schemes for arbitrarily permuted parallel channels where the component channels are memoryless, binary-input, and output-symmetric.

Accelerated Bilateral Filtering With Block Skipping

Abstract: We propose a method to accelerate Yang's real-time O(1) bilateral filtering algorithm, based on the observation that in the original algorithm, some of the computation can be strategically eliminated. To identify such computation, the algorithm steps are analyzed in conjunction with its recursive Gaussian filtering component. By block partitioning the image, the procedure to isolate these unnecessary computation is simplified, and the proposed algorithm only needs to skip some of the image blocks when performing recursive linear filtering. The resultant accelerated algorithm is able to achieve 1.5~5 times speedup, depending on the image statistics and the filtering parameters. The proposed algorithm only marginally degrades the accuracy of the filtering, and the simplicity and small memory footprint of Yang's original algorithm are largely maintained.

Distributed storage evaluation on a three-wide inter-data center deployment

Abstract: The demand for cloud storage is exploding as an ever increasing number of enterprises and consumers are storing and processing their data in the cloud. Hence, distributed object storage solutions (e.g., QFS, Swift, HDFS) are becoming very critical components of any cloud infrastructure. These systems are able to offer good reliability by distributing redundant information across a large number of commodity servers, making it possible to achieve 10 nines and beyond with relative ease. One drawback of these systems is that they are usually designed for deployment within a single data center, where node-to-node latencies are small. Geo-replication (i.e., distributing redundant information across data centers) for most open-source storage systems is, to the best of our knowledge, accomplished by asynchronously mirroring a given deployment. Given that geo-replication is critical for ensuring very high degrees of reliability (e.g., for achieving 16 nines), in this work we evaluate how these storage systems perform when they are directly deployed in a WAN setting. To this end, three popular distributed object stores, namely Quantcast-QFS, Swift and Tahoe-LAFS, are considered and tested in a three-wide data center environment and our findings are reported.

Gaussian state amplification with noisy state observations

Abstract: The problem of simultaneous message transmission and state amplification in a Gaussian channel with additive Gaussian state is studied when the sender has imperfect non-causal knowledge of the state sequence. Inner and outer bounds to the rate-state-distortion region are provided. The coding scheme underlying the inner bound combines analog signaling and Gelfand-Pinsker coding, where the latter deviates from the operating point of Costa's dirty paper coding.

Exact-Repair Regenerating Codes Via Layered Erasure Correction and Block Designs

Abstract: A new class of exact-repair regenerating codes is constructed by combining two layers of erasure correction codes together with combinatorial block designs, e.g., Steiner systems, balanced incomplete block designs and t-designs. The proposed codes have the "uncoded repair" property where the nodes participating in the repair simply transfer part of the stored data directly, without performing any computation. The layered error correction structure makes the decoding process rather straightforward, and in general the complexity is low. We show that this construction is able to achieve performance better than time-sharing between the minimum storage regenerating codes and the minimum repair-bandwidth regenerating codes.

Method and apparatus for image filtering

Abstract: A system that incorporates the subject disclosure may include, for example, partitioning the image into a group of blocks, calculating principle bilateral filtered image components for a first subset of the group of blocks where the principle bilateral filtered image components are not calculated for a second subset of the group of blocks, and applying an infinite impulse response filter to the image using the principle bilateral filtered image components. Other embodiments are disclosed.

A probabilistic pairwise-preference predictor for image quality

Abstract: Current image quality estimators (QEs) compute a single score to estimate the perceived quality of a single input image. When comparing image quality between two images with such a QE, one only knows which image has a higher score; there is no knowledge about the uncertainty of these scores or what fraction of viewers might actually prefer the image with the lower score. In this paper, we present a Probabilistic Pairwise Preference Predictor (P4) that estimates the probability that one image will be preferred by a random viewer relative to a second image. We train a multilevel Bayesian logistic regression model using results from a large-scale subjective test and present the degree to which various factors influence subjective quality. We demonstrate our model provides well-calibrated estimates of pairwise image preferences using a validation set comprising pairs with 60 reference images outside the training set.

Worst-Case Expected-Capacity Loss of Slow-Fading Channels

Abstract: For delay-limited communication over block-fading channels, the difference between the ergodic capacity and the maximum achievable expected rate for coding over a finite number of coherent blocks represents a fundamental measure of the penalty incurred by the delay constraint. This paper introduces a notion of worst-case expected-capacity loss. Focusing on the slow-fading scenario (one-block delay), the worst-case additive and multiplicative expected-capacity losses are precisely characterized for the point-to-point fading channel. Extension to the problem of writing on fading paper is also considered, where both the ergodic capacity and the additive expected-capacity loss over one-block delay are characterized to within one bit per channel use.

Characterizing the Rate Region of the (4,3,3) Exact-Repair Regenerating Codes

Abstract: Exact-repair regenerating codes are considered for the case (n,k,d)=(4,3,3), for which a complete characterization of the rate region is provided. This characterization answers in the affirmative the open question whether there exists a non-vanishing gap between the optimal bandwidth-storage tradeoff of the functional-repair regenerating codes (i.e., the cut-set bound) and that of the exact-repair regenerating codes. To obtain an explicit information theoretic converse, a computer-aided proof (CAP) approach based on primal and dual relation is developed. This CAP approach extends Yeung's linear programming (LP) method, which was previously only used on information theoretic problems with a few random variables due to the exponential growth of the number of variables in the corresponding LP problem. The symmetry in the exact-repair regenerating code problem allows an effective reduction of the number of variables, and together with several other problem-specific reductions, the LP problem is reduced to a manageable scale. For the achievability, only one non-trivial corner point of the rate region needs to be addressed in this case, for which an explicit binary code construction is given.

Gaussian State Amplification with Noisy State Observations

Abstract: The problem of simultaneous message transmission and state amplification in a Gaussian channel with additive Gaussian state is studied when the sender has imperfect noncausal knowledge of the state sequence. Inner and outer bounds to the rate--state-distortion region are provided. The coding scheme underlying the inner bound combines analog signaling and Gelfand-Pinsker coding, where the latter deviates from the operating point of Costa's dirty paper coding.