Parallelization of web processing services on cloud computing: A case study of Geostatistical Methods

Dissertation submitted in partial fulfillment of the requirements for the Degree of Master of Science in Geospatial Technologies.In the last decade the publication of geographic information has increased in Internet, especially with the emergence of new technologies to share information. This information requires the use of technologies of geoprocessing online that use new platforms such as Cloud Computing. This thesis work evaluates the parallelization of geoprocesses on the Cloud platform Amazon Web Service (AWS), through OGC Web Processing Services (WPS) using the 52North WPS framework. This evaluation is performed using a new implementation of a Geostatistical library in Java with parallelization capabilities. The geoprocessing is tested by incrementing the number of micro instances on the Cloud through GridGain technology. The Geostatistical library obtains similar interpolated values compared with the software ArcGIS. In the Inverse Distance Weight (IDW) and Radial Basis Functions (RBF) methods were not found differences. In the Ordinary and Universal Kriging methods differences have been found of 0.01% regarding the Root Mean Square (RMS) error.The parallelization process demonstrates that the duration of the interpolation decreases when the number of nodes increases. The duration behavior depends on the size of input dataset and the number of pixels to be interpolated. The maximum reduction in time was found with the largest configuration used in the research (1.000.000 of pixels and a dataset of 10.000 points). The execution time decreased in 83% working with 10 nodes in the Ordinary Kriging and IDW methods. However, the differences in duration working with 5 nodes and 10 nodes were not statistically significant. The reductions with 5 nodes were 72% and 71% in the Ordinary Kriging and IDW methods respectively. Finally, the experiments show that the geoprocessing on Cloud Computing is feasible using the WPS interface. The performance of the geostatistical methods deployed through the WPS services can improve by the parallelization technique. This thesis proves that the parallelization on the Cloud is viable using a Grid configuration. The evaluation also showed that parallelization of geoprocesses on the Cloud for academic purposes is inexpensive using Amazon AWS platform

Middleware-based Database Replication: The Gaps between Theory and Practice

The need for high availability and performance in data management systems has been fueling a long running interest in database replication from both academia and industry. However, academic groups often attack replication problems in isolation, overlooking the need for completeness in their solutions, while commercial teams take a holistic approach that often misses opportunities for fundamental innovation. This has created over time a gap between academic research and industrial practice. This paper aims to characterize the gap along three axes: performance, availability, and administration. We build on our own experience developing and deploying replication systems in commercial and academic settings, as well as on a large body of prior related work. We sift through representative examples from the last decade of open-source, academic, and commercial database replication systems and combine this material with case studies from real systems deployed at Fortune 500 customers. We propose two agendas, one for academic research and one for industrial R&D, which we believe can bridge the gap within 5-10 years. This way, we hope to both motivate and help researchers in making the theory and practice of middleware-based database replication more relevant to each other.Comment: 14 pages. Appears in Proc. ACM SIGMOD International Conference on Management of Data, Vancouver, Canada, June 200

Improving Multicast Communications Over Wireless Mesh Networks

In wireless mesh networks (WMNs) the traditional approach to shortest path tree based multicasting is to cater for the needs of the poorest performingnode i.e. the maximum permitted multicast line rate is limited to the lowest line rate used by the individual Child nodes on a branch. In general, this meansfixing the line rate to its minimum value and fixing the transmit power to its maximum permitted value. This simplistic approach of applying a single multicast rate for all nodes in the multicast group results in a sub-optimal trade-off between the mean network throughput and coverage area that does not allow for high bandwidth multimedia applications to be supported. By relaxing this constraint and allowing multiple line rates to be used, the mean network throughput can be improved. This thesis presents two methods that aim to increase the mean network throughput through the use of multiple line rates by the forwarding nodes. This is achieved by identifying the Child nodes responsible for reducing the multicast group rate. The first method identifies specific locations for the placement of relay nodes which allows for higher multicast branch line rates to be used. The second method uses a power control algorithm to tune the transmit power to allow for higher multicast branch line rates. The use of power control also helps to reduce the interference caused to neighbouring nodes.Through extensive computer simulation it can be shown that these two methods can lead to a four-fold gain in the mean network throughput undertypical WMN operating conditions compared with the single line rate case