6. Conclusion and future work
In this paper, a privacy-preserving participant coordi- nation mechanism is proposed to both achieve optimal QoI for sensing tasks, and protect the location privacy of participants. Specifically, the cooperation among partici- pants are used to replace the traditional centralized partic- ipant coordination phase. An optimization problem is for- mulated to select participants iteratively to maximize the QoI satisfaction ratio and privacy level while fulfilling the constraints of incentive. Based on this, an approximate so- lution is proposed based on Borda Ranking method. A co- operative data aggregation method is further proposed to protect participant privacy through the whole data collec- tion procedure. And a punishment mechanism is proposed to ensure continuous operation of the whole system. Ex- tensive simulation results, based on a real trace dataset of taxi in Rome, showed the effectiveness and robustness of our approach. In the future, we plan to further consider the reputa- tion of participants for our punishment mechanism to en- sure the data quality. Extensively, we will consider not only the privacy protection issue but also the security issues in such systems. For example, we would like to investi- gate how to protect the privacy of participants when the registration server pretends itself as a smart device to spy on the trajectory information of other participants. Mean- while, we plan to explore how to further strengthen the privacy protection strategy to prevent privacy leaks in the process of information exchange between participants and server cloud.