Participatory sensing is a rising paradigm which utilizes mobile phones to collect data and build application on the cloud. But there are many problems to be resolved, poor quality of received information caused by task executors has been one of them. So incentive mechanism is essential for attracting users to participate in and submit high-quality data. Inspired by contract theory, we model participatory sensing as a contractual relationship and devote to design reasonable rewards for relevant results to maximize the benefit of task publisher. Under complete information scenario where task executors' efforts can be observed and incomplete information scenario where task executors' efforts can not be observed, we take advantage of maximization problem to infer the optional contract reward for task executors. In addition, based on the utility of task publisher, we propose optimal effort and optimal effort discriminant inequality (OEDI). Furthermore, we discuss the influence of noise, cost and boundary on optimal effort from aspects of theory and reality. Finally, we evaluate our contract-based approach by thorough simulations to show its effectiveness and accuracy.
