1 Introduction
The integration of sensors and embedded computing devices triggers the emergence of mobile crowdsensing [2], in which user-centric mobile devices, e.g., smartphones, in-vehicle devices and wearable devices, are utilized to sense, collect and process data about social events and phenomena. This “sensing as a service” [3] elaborates our knowledge of the physical world by opening up a new door for data collection and sharing [4]. Due to the increasing popularity of mobile devices, mobile crowdsensing supports a broad range of sensing applications nowadays, ranging from social recommendation, such as restaurant recommendation, parking space discovery and indoor floor plan reconstrction [5], to environment monitoring, such as air quality measurement, noise level detection and dam water release warning. With human intelligence and user mobility, mobile crowdsensing can significantly improve the trustworthiness of sensing data, extend the scale of sensing applications and reduce the cost on high-quality data collection [6].