29989378
Circular shifted transmit diversity
Three design requirements of space-time block code, full diversity order, full data rate and orthogonality, cannot be achieved simultaneously when the number of transmit antenna is more than two. In this paper, we propose a transmit diversity scheme—circular shifted transmit diversity (CSTD). CSTD can always achieve the full data rate and has very low decoding complexity. Through the performance analysis and simulation comparison in the case of same spectrum efficiency between CSTD and other well-known proposed schemes, it can be proved that CSTD always significantly outperforms the other transmit diversity schemes with full data rate. Additionally, compared with the transmit diversity schemes with full diversity order, CSTD has lower complexity and approximately the same performance when channel coding is concatenated. Copyright © 2004 John Wiley & Sons, Ltd.
9960122
Dynamic Zone-Balancing of Topology-Aware Peer-to-Peer Networks
Building a topology-aware peer-to-peer overlay network can bring many advantages, such as providing locality-aware connectivity and reducing routing path length. While its benefits on performance have been recognized, an uneven overlay zone distribution has emerged. Recent work has shown that topology-aware neighbor selection during construction can aggravate the unbalance of zone distribution while it reduces routing path length. The imbalance in zone sizes may lead to performance decrease and an unfair load distribution. 
 
In this paper, we present an even topology-aware peer-to-peer network based on De Bruijn Graph by developing a dynamic zone-balancing approach.
18105952
Adapting Prime Number Labeling Scheme for Directed Acyclic Graphs
Directed Acyclic Graph(DAG) could be used for modeling subsumption hierarchies. Several labeling schemes have been proposed or tailored for indexing DAG in order to efficiently explore relationships in such hierarchy. However few of them can satisfy all the requirements in response time, space, and effect of updates simultaneously. In this paper, the prime number labeling scheme is extended for DAG. The scheme invests intrinsic mapping between integer divisibility and subsumption hierarchy, which simplifies the transitive closure computations and diminishes storage redundancy, as well as inherits the dynamic labeling ability from original scheme. Performance is further improved by introducing some optimization techniques. Our extensive experimental results show that prime number labeling scheme for DAG outperforms interval-based and prefix-based labeling schemes in most cases.
4178545
Data placement and query processing based on RPE parallelisms
The basic idea behind parallel database systems is to perform operations in parallel to reduce the response time and improve the system throughput. Data placement is a key factor on the performance of parallel database systems. This paper proposes two data partition strategies to decluster XML documents with very large size, path schema based path instance balancing (PSPIB) strategy, in which all path instances with the same path schema in a data tree are declustered evenly over all sites, and node schema based node round-robin (NSNRR) strategy, in which all node objects with the same node schema in a data tree are declustered over all sites in a round-robin way. Accordingly, two query processing algorithms are proposed based on the two partition methods, parallel path merge (PPM) algorithm and parallel pipelining path join (PPPJ) algorithm. The performance analysis and evaluation on the two data placement strategies and corresponding query processing algorithms are given in this paper.
2388375
Congestion control via online sampling
We consider the congestion control problem in a communication network with multiple traffic sources, each modeled as a fully-controllable stream of fluid traffic. The controlled traffic shares a common bottleneck node with high-priority cross traffic described by a Markov-modulated fluid (MMF). Each controlled source is assumed to have a unique round-trip delay. We wish to maximize a linear combination of the throughput, delay, traffic loss rate, and a fairness metric at the bottleneck node. We introduce an online sampling-based burst-level congestion control scheme capable of performing effectively under rapidly-varying cross traffic by making explicit use of the provided MMF model of that variation. The control problem is posed as a finite-horizon Markov decision process and is solved heuristically using a technique called hindsight optimization. We provide a detailed derivation of our congestion control algorithm based on this technique. The distinguishing feature of our scheme relative to conventional congestion control schemes is that we exploit a stochastic model of the cross traffic. Our empirical study shows that our control scheme significantly outperforms the conventional proportional-derivative (PD) controller, achieving higher utilization, lower delay, and lower loss under reasonable fairness. The performance advantage of our scheme over the PD scheme grows as the rate variance of cross traffic increases, underscoring the effectiveness of our control scheme under variable cross traffic.
1677219
Application of Smodels in Quartet Based Phylogeny Construction
Evolution is an important sub-area of study in biological science, where given a set of taxa, the goal is to reconstruct their evolutionary history, or phylogeny. One very recent approach is to predict a local phylogeny for every subset of 4 taxa, called a quartet topology, and then to assemble a phylogeny for the whole set of taxa satisfying these predicted quartet topologies. In general, the predicted quartet topologies might not always agree with each other, and thus the objective function becomes to satisfy a maximum number of them. This is the well known Maximum Quartet Consistency (MQC) problem. In the past, the MQC problem has been solved by dynamic programming and the so-called fixed-parameter method. Recently, we have proposed to solve the MQC in answer set programming. In this note, we summarize the theoretical results of this approach and report new experimental results for the purpose of comparison, which show that our approach in answer set programming is favored over the existing approaches based on dynamic programming and fixed-parameter method. In particular, some of the hard instances (where the error ratio is high) that were not reported to be solved in other approaches can now be solved in our approach.
6594297
Generic Universal Switch Blocks
A switch block M with W terminals on each side is said to be universal if every set of nets satisfying the dimension constraint (i.e., the number of nets on each side of M is at most W) is simultaneously routable through M. In this paper, we present an algorithm to construct N-sided universal switch blocks with W terminals on each side. Each of our universal switch blocks has (/sub 2//sup N/) W switches and switch-block flexibility N-1 (i.e., F/sub S/=N-1). We prove that no switch block with less than (/sub 2//sup N/)W switches can be universal. We also compare our universal switch blocks with others of the topology associated with Xilinx XC4000-type FPGAs. To explore the area performance of the universal switch blocks, we develop a detailed router for hierarchical FPGAs (HFPGAs) with 5-sided switch blocks. Experimental results demonstrate that our universal switch blocks improve routability at the chip level. Based on extensive experiments, we also provide key insights into the interactions between switch-block architectures and routing.
1638130
Bounding computably enumerable degrees in the Ershov hierarchy
Nanyang Technol Univ, Sch Math & Phys Sci, Div Math Sci, Singapore 639798, Singapore. Chinese Acad Sci, Inst Software, Beijing 100080, Peoples R China. Natl Univ Singapore, Dept Math, Singapore 119260, Singapore.
39007433
Presentations of K-Trivial Reals and Kolmogorov Complexity
For given real α ∈ {0,1}∞, a presentation V of α is a prefix-free and recursively enumerable subset of {0,1}* such that $\alpha = \Sigma_{\sigma\epsilon\nu}2^{-|\sigma|}$. So, α has a presentation iff α is a left-r.e. real.
35293254
Quasi-complements of the cappable degrees
Say that a nonzero c. e. degree b is a quasi-complement of a c. e. degree a if a ∩ b = 0 and a ∪ b is high. It is well-known (due to Shore) that each cappable degree has a high quasi-complement. However, by the existence of the almost deep degrees, there are nonzero cappable degrees having no low quasi-complements. In this paper, we prove that any nonzero cappable degree has a low2 quasi-complement. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
8102710
Degrees of d. c. e. reals
A real α is called a c. e. real if it is the halting probability of a prefix free Turing machine. Equivalently, α is c. e. if it is left computable in the sense that L(α) = {q ∈ ℚ : q ≤ α} is a computably enumerable set. The natural field formed by the c. e. reals turns out to be the field formed by the collection of the d. c. e. reals, which are of the form α—β, where α and β are c. e. reals. While c. e. reals can only be found in the c. e. degrees, Zheng has proven that there are Δ02 degrees that are not even n-c. e. for any n and yet contain d. c. e. reals, where a degree is n-c. e. if it contains an n-c. e. set. In this paper we will prove that every ω-c. e. degree contains a d. c. e. real, but there are ω + 1-c. e. degrees and, hence Δ02 degrees, containing no d. c. e. real. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)