Characterization and Performance Analysis of LTE-Advanced Uplink Signals in Presence of Amplifier Nonlinearity

Carrier aggregation (CA) is the new technique standardized for the next generation of cellular networks, namely long term evolution-advanced (LTE-Advanced) in response to the continuous demands of increased data rates. One of the challenges facing the new CA technique is the increased dynamic range of the transmitted uplink (UL) signal that represents the sum of different carrier components in the time domain. This increased dynamic range makes the signal more susceptible to nonlinear distortion caused by nonlinear devices at the transmitter and eventually leads to performance degradation. In this paper, we investigate the effect of the nonlinear distortion on the UL of LTE-Advanced. Towards this investigation, statistical characterization of the UL signal is conducted, where it is established that it has a quasi-Gaussian characteristics. Also, statistical characterization of the nonlinear distortion noise at the receiver detector is performed, where it appears evident that it can be regarded as a complex Gaussian process. Through these characterizations, an analytical expression for the bit error rate, as a function of the system parameters and the input back-off level, is derived. The analytical results are validated via simulation results, where the good agreements confirm the pursued approach and the taken assumptions.     

Ethanol from lactose in salted cheese whey by recombinant Saccharomyces cerevisiae

Seven yeast recombinants were selected from 57 fusant colonies on the basis of higher DNA content, nuclear diameter and ethanol yield compared to parental Saccharomyces cerevisiae ATCC 4126 and Kluyveromyces lactis CBS 683. Six recombinants out of the above colonies revealed growth on lactose and sucrose, indicating that they are S. cerevisiae with transformed β-galactosidase systems. The fusant colonies were investigated with respect to their capacity to convert lactose in salted cheese whey into ethanol. Among these recombinants that showed high tolerance towards sodium chloride and higher ethanol yield than lactose fermenting parental K. lactis CBS 683, SK-1 exhibited high tolerance up to 4 g dl^–1 sodium chlonride with an ethanol yield of 4.66 ml dl^–1 (v/v) , SK-23 tolerated 6 g dl^–1 sodium chloride with an ethanol yield of 4.14 ml dl^–1 (v/v) and SK-26 showed resistance towards 8 g dl^–1 sodium chloride and give an ethanol yield of 3 ml dl^–1 (v/v).     

Ring of Masters (ROM): A new ring structure for Bluetooth scatternets with dynamic routing and adaptive scheduling schemes

This paper attempts to address the scatternet problem in Bluetooth through a comprehensive approach. We propose a new decentralized ring structure to combat the formation of traffic bottlenecks. The adopted construction protocol ensures flexibility of node selection and a good level of fault tolerance. The routing protocol combines both simplicity and robustness by taking advantage of the ring structure and relying on the collective memory of piconets to make forwarding and discarding decisions. The intra- and inter-piconet scheduling algorithm, called ROM adaptive scheduling (RAS), dynamically allocates time slots and is responsive to the varying workload conditions. We demonstrate, through analysis and simulations, that the various components of ROM yield a system that has good performance in terms of throughput, latency, delivery, and link utilization.     

The ParTriCluster Algorithm for Gene Expression Analysis

Analyzing gene expression patterns is becoming a highly relevant task in the Bioinformatics area. This analysis makes it possible to determine the behavior patterns of genes under various conditions, a fundamental information for treating diseases, among other applications. A recent advance in this area is the Tricluster algorithm, which is the first algorithm capable of determining 3D clusters (genes × samples × timestamps), that is, groups of genes that behave similarly across samples and timestamps. However, even though biological experiments collect an increasing amount of data to be analyzed and correlated, the triclustering problem remains a bottleneck due to its NP-Completeness, so its parallelization seems to be an essential step towards obtaining feasible solutions. In this work we propose and evaluate the implementation of a parallel version of the Tricluster algorithm using the filter-labeled-stream paradigm supported by the Anthill parallel programming environment. The results show that our parallelization scales well with the data size, being able to handle severe load imbalances that are inherent to the problem. Further more, the parallelization strategy is applicable to any depth-first searches.     

A Variance Equality Test for Two Correlated Complex Gaussian Variables With Application to Spectral Power Comparison

Complex-valued Gaussian distributions occur frequently in signal processing. We derive a simple statistic, independent of any complex-valued correlation, for testing for the equality of variances using a sample drawn from such a bivariate distribution. The percentage points of the distribution are easy to compute. The power of the test is determined and shown to be high even for very small sample sizes when the variables are highly correlated. The new test is used to determine whether the spectral power associated with an ultralow-frequency wave in the solar magnetic field is equal at two different observing spacecraft     

Efficient algorithms for mining closed itemsets and their lattice structure

The set of frequent closed itemsets uniquely determines the exact frequency of all itemsets, yet it can be orders of magnitude smaller than the set of all frequent itemsets. In this paper, we present CHARM, an efficient algorithm for mining all frequent closed itemsets. It enumerates closed sets using a dual itemset-tidset search tree, using an efficient hybrid search that skips many levels. It also uses a technique called diffsets to reduce the memory footprint of intermediate computations. Finally, it uses a fast hash-based approach to remove any "nonclosed" sets found during computation. We also present CHARM-L, an algorithm that outputs the closed itemset lattice, which is very useful for rule generation and visualization. An extensive experimental evaluation on a number of real and synthetic databases shows that CHARM is a state-of-the-art algorithm that outperforms previous methods. Further, CHARM-L explicitly generates the frequent closed itemset lattice.     

A new taxonomy of routing algorithms for wireless mobile ad hoc networks: the component approach

Over the past decade, wireless multihop ad hoc networks have received a tremendous amount of research focus, at the core of which lies the design problem for efficient routing algorithms to meet various scenarios and applications. The axiom, "one size doesn't fit all," continues to stand firmly to this day. In light of this, we introduce a new routing design concept - the component approach. We examine existing routing protocols and break them down into smaller building blocks, namely, routing components. The component analysis and classification results show that most routing protocols can be functionally decomposed into several basic routing components. This fact indicates that it is feasible to design a component-based routing (CBR) protocol. With a different realization for each basic routing component, it is expected that the routing behavior of CBR can be tailored to different application profiles and time-varying environment parameters at a reasonable cost     

Load-Balanced Sparse Matrix–Vector Multiplication on Parallel Computers

We considered the load-balanced multiplication of a large sparse matrix with a large sequence of vectors on parallel computers. We propose a method that combines fast load-balancing with efficient message-passing techniques to alleviate computational and inter-node communications challenges. The performance of the proposed method was evaluated on benchmark as well as on synthetically generated matrices and compared with the current work. It is shown that, by using our approach, a tangible improvement over prior work can be obtained, particularly for very sparse and skewed matrices. Moreover, it is also shown that I/O overhead for this problem can be efficiently amortized through I/O latency hiding and overall load-balancing.