Accessing Geospatial Services in Limited Bandwidth Service-Oriented Architecture (SOA) Environments.

摘要

First responders are continuously moving at an incident site and this movement requires them to access Service-Oriented Architecture services, such as a Web Map Service, via mobile wireless networks. First responders from inside a building often have problems in communicating to devices outside that building due to propagation obstacles. Dynamic user geometry and the propagation conditions of communicating from inside buildings to transceivers on the outside are difficult to model reliably in network planning software. Thus, leading commercial network simulation software and open source network simulator software do not model wireless links between transceivers inside and outside of buildings; new modeling software is needed.;The discrete simulation runs in this investigation were built on events in a scenario that is typical of first-responder activities at an incident site. This scenario defined the geometry and node characteristics that were used in a mobile wireless network simulation to calculate expected connectivity based on propagation modeling, transceiver characteristics, and the environment.;The author implemented in software a propagation model from the United States National Institute of Standards and Technology (NIST) to simulate radio wave propagation path loss during the scenario. Modifications to the NIST model propagation path loss method were generated to improve consistency in results calculated with the same node separation distances and radio wave obstacle environments. The final set of modifications made the NIST model more generalized by using more building material characteristics than the original version. The modifications in this study to the path loss model from NIST engineers were grounded on ad hoc network connectivity data collected at the operational scenario site. After changes in the NIST model were validated, 1,265 operational simulation runs were conducted with different numbers of deployed nodes in an operational incident-response scenario. Data were reduced and analyzed to compare measures of mobile ad hoc network effectiveness.;Findings in this investigation resulted in two specific contributions to the body of knowledge in mobile wireless network design. First, data analysis indicated that specific changes to a recent path loss model from NIST produced results that were more generalized than the original model with respect to accommodating different building materials and enhancing the consistency of simulation results. Second, the results from the modified path loss model revealed an operational impact in using relay nodes to support public safety. Specifically, placing relay nodes at the entrance to a building and on odd-numbered floors improved connectivity in terms of first responders' accessing Web Services via mobile network devices, when moving through a building in an incident scenario.