*3.2. Data Crowdsourcing Incentive Mechanism*

One of the objectives of the proposed system is to create the basis for a mHealth data crowdsourcing ecosystem that can be harnessed by third parties in order to improve the existing knowledge and research on DM. To achieve such an objective, it is essential to motivate the patients to upload their CGM sensor data to the decentralized storage nodes so that anyone, once authorized, can access them.

The first incentive measure to ease this data collection process is its automation, which is carried out by the devised CGM-based IoT system. Thus, after setting up the system (i.e., after installing the required fog gateways and the smartphone app), the user only has to check his/her glucose levels. The rest of the processes (e.g., data processing/uploading/distribution, notifications) do not require the user intervention.

The second incentive measure is related to patients that may not be willing to share their data publicly or for free through the proposed crowdsourcing platform. In such a case, the blockchain allows for implementing a private system where patients receive some sort of reward when they contribute with their mHealth data, so the more data they add to the system, the higher the reward.

The reward system is based on the use of a metacoin, which is a digital cryptocurrency that uses an already-deployed blockchain, but which implements additional transaction logic over such a blockchain. For this article, a metacoin called GlucoCoin (G) was created on the Ethereum blockchain. GlucoCoin requires creating a digital wallet for every participant and implements all the software

operations needed by a cryptocurrency, which essentially involve getting the balance from a user and sending an amount from one user to another.

GlucoCoin can be used not only for rewarding the users for their data, but it can be used by them to purchase items or services. For instance, as it is later described in Section 4.2, patients may use their GlucoCoins to automate the purchase of new CGM sensors when they are going to expire.
