A CrowdService: Optimizing Mobile Crowdsourcing and Service Composition
A participatory mobile sensing system is designed to enable clients to voluntarily collect environmental data using embedded sensors and a mobile device while going about their daily activities. Due to the spatio-temporal nature of the data, and the significant benefits of the data to the general public, it is necessary to employ an efficient and effective query processing model for the mobile clients to access the data that can be visualized via an interactive multimedia interface. This article introduces a unified on-demand and data broadcast model to serve queries in the context of a mobile sensing system. The contributions of this article include the following: (i) it presents a novel data structure and indexing method to support the system; (ii) it provides flexibility for the client to issue query using on-demand or broadcast channel according to the server load and broadcast schedule; (iii) it enables new data access and processing for the mobile client; and (iv) it is designed for a multiple channels/receivers environment in a 4G wireless network. The proposed model uses a holistic query processing approach for the mobile sensing system that offers substantial efficiency and autonomy for mobile clients when retrieving data. The results of the experiments undertaken affirm the effectiveness of its performance.