15547965
An efficient and accurate method for evaluating time series similarity
A variety of techniques currently exist for measuring the similarity between time series datasets. Of these techniques, the methods whose matching criteria is bounded by a specified ε threshold value, such as the LCSS and the EDR techniques, have been shown to be robust in the presence of noise, time shifts, and data scaling. Our work proposes a new algorithm, called the Fast Time Series Evaluation (FTSE) method, which can be used to evaluate such threshold value techniques, including LCSS and EDR. Using FTSE, we show that these techniques can be evaluated faster than using either traditional dynamic programming or even warp-restricting methods such as the Sakoe-Chiba band and the Itakura Parallelogram.
 We also show that FTSE can be used in a framework that can evaluate a richer range of ε threshold-based scoring techniques, of which EDR and LCSS are just two examples. This framework, called Swale, extends the ε threshold-based scoring techniques to include arbitrary match rewards and gap penalties. Through extensive empirical evaluation, we show that Swale can obtain greater accuracy than existing methods.
5243557
Data Morphing: An Adaptive, Cache-Conscious Storage Technique
The number of processor cache misses has a critical impact on the performance of DBMSs running on servers with large main-memory configurations. In turn, the cache utilization of database systems is highly dependent on the physical organization of the records in main-memory. A recently proposed storage model, called PAX, was shown to greatly improve the performance of sequential file-scan operations when compared to the commonly implemented N-ary storage model. However, the PAX storage model can also demonstrate poor cache utilization for other common operations, such as index scans. Under a workload of heterogenous database operations, neither the PAX storage model nor the N-ary storage model is optimal. 
 
In this paper, we propose a flexible data storage technique called Data Morphing. Using Data Morphing, a cache-efficient attribute layout, called a partition, is first determined through an analysis of the query workload. This partition is then used as a template for storing data in a cache-efficient way. We present two algorithms for computing partitions, and also present a versatile storage model that accommodates the dynamic reorganization of the attributes in a file. Finally, we experimentally demonstrate that the Data Morphing technique provides a significant performance improvement over both the traditional N-ary storage model and the PAX model.
2021327
A Cross-Layer Architecture to Exploit Multi-Channel Diversity with a Single Transceiver
The design of multi-channel multi-hop wireless mesh networks is centered around the way nodes synchronize when they need to communicate. However, existing designs are confined to the MAC layer -they are based on either negotiation on a rendezvous control channel, or on optimistic synchronization. Both approaches scale poorly as the network grows in coverage and density. The rendezvous control channel may become the bottleneck, while optimistic synchronization may incur substantial overhead - especially amongst nodes close to a gateway, where the mesh traffic converges. In this paper, we describe Dominion - a cross-layer architecture that includes both medium access control and routing. At the MAC layer, a node switches channels in a deterministic manner to address the scalability issue. At the network layer, a Dominion node routes traffic along the shortest distance across both spatial and frequency domains, based on the deterministic channel-hopping schedule and network connectivity. Since the shortest distance path across the frequency domain is time variant, Dominion naturally spreads the packets of the same flow across multiple paths, relieving the intra-flow and inter-flow contention, and improving throughput. Through QualNet simulations we show that Dominion is able to achieve, on average, 1813% higher aggregate distance-normalized throughput than IEEE 802.11, while being 1730% fairer (using Jain's fairness index) with 50 simultaneous random flows.