Smart cities use Information and Communication Technologies (ICT) to enrich existing public services and to improve citizens’ quality of life. In this scenario, Mobile CrowdSensing (MCS) has become, in the last few years, one of the most prominent paradigms for urban sensing. MCS allow people roaming around with their smart devices to collectively sense, gather, and share data, thus leveraging the possibility to capture the pulse of the city. That can be very helpful in emergency scenarios, such as the COVID-19 pandemic, that require to track the movement of a high number of people to avoid risky situations, such as the formation of crowds. In fact, using mobility traces gathered via MCS, it is possible to detect crowded places and suggest people safer routes/places. In this work, we propose an edge-anabled mobile crowdsensing platform, called ParticipAct, that exploits edge nodes to compute possible dangerous crowd situations and a federated blockchain network to store reward states. Edge nodes are aware of all critical situation in their range and can warn the smartphone client with a smart push notification service that avoids firing too many messages by adapting the warning frequency according to the transport and the specific subarea in which clients are located.

智慧城市利用信息和通信技术（ICT）来丰富现有的公共服务并提高公民的生活质量。在这种情况下，移动人群感知（MCS）在过去几年中已成为城市感知最突出的范例之一。 MCS让人们带着智能设备四处漫游，共同感知、收集和共享数据，从而有可能捕捉城市的脉搏。这在紧急情况下非常有帮助，例如 COVID-19 大流行，因为需要跟踪大量人员的活动以避免出现人群聚集等危险情况。事实上，使用通过 MCS 收集的移动轨迹，可以检测拥挤的地方并建议人们更安全的路线/地点。在这项工作中，我们提出了一个名为 ParticipAct 的边缘移动人群感知平台，它利用边缘节点来计算可能的危险人群情况，并利用联合区块链网络来存储奖励状态。边缘节点了解其范围内的所有紧急情况，并可以通过智能推送通知服务向智能手机客户端发出警告，该服务通过根据传输和客户端所在的特定分区调整警告频率来避免触发过多消息。