### Industry 4.0 IIoT, Cloud, and Edge Computing for Next-Generation Offshore Wind Farms
By enabling real-time data processing and immediate response capabilities, edge computing enhances operational efficiency, improves safety, and reduces maintenance costs [48]. These benefits are crucial for the sustainable operation of wind farms and underscore the growing importance of integrating advanced computational technologies in renewable energy systems. Designing scalable IIoT-Edge data-acquisition systems using the publish/subscribe model allows a form of asynchronous messaging where the publishers or data producers are decoupled from the subscribers or data consumers [49]. In this model, publishers send messages to a message broker, which stores messages in topics [50], and the subscribers then subscribe to these topics. Depending on the requirements of the wind farm operator, it is likely that they may add or remove publishers or subscribers from the IIoT-Edge data-acquisition system illustrated in Figure 3. This model excels in scalability for wind farms' data-acquisition systems, as it allows the number of publishers to be changedwithout impacting the subscribers, due to its non-reliance on a 1:1 publisher-to-subscriber mapping [46]. There are key IoT protocols that support the publish/subscribe model for machine-to-machine communication in industrial IoT environments. [PERSON] et al. [51] quantify the adoption of these IoT protocols at the IoT-cloud platform level with MQTT at 31%, AMQP at 19%, COAP at 13%, and OPC-UA at 6%. The choice of IoT protocol emerges as an important challenge for application developers who must choose one of the many lightweight communication protocols for a resource-constrained environment: ISO 19464 Advanced Message Queueing Protocol (AMQP), also known as \"Internet protocol for business messaging\" is an open standard lightweight message-based protocol that assists cross-platform application communication. It supports the publish/subscribe model alongside the request/respond model and the store-and-forward model [52; 53]. The AMQP supports asynchronous communication by connecting its brokers and applications in a star design. Further, it integrates quality of service (QoS) features, requiring that all applications know the broker's URL. Unfortunately, AMQP requires more bandwidth resources than its counterparts and may not be suitable in resource-constrained environments. IBM's OASIS standard Message Queueing Telemetry Transport (MQTT) is designed with a small code footprint with minimal bandwidth requirements, making it suitable for deployment in low-power, resource-constrained machine-to-machine communication scenarios [54; 55]. Unlike AMQP, MQTT considers multiple QoS levels (such as QoS level 1: _\"fire-and-forget\"_; QoS level 2: _\"at least once\"_; and QoS level 3: _\"exactly once\"_) [53]. Further, it is quite scalable and finds applications in scenarios with several small, constrained devices with more reliability requirements than speed [56]. Common examples of MQTT in offshore wind include the use of the MQTT Sparkplug in optimizing SCADA implementations. Internet Engineering Task Force (IETF) RFC-7252 Constrained Application Protocol (CoAP) is a specialized User Datagram Protocol (UDP) web transfer protocol for use with constrained nodes and constrained networks in industrial IoT environments such as advanced metering in digital substations in the smart energy domain and building automation [7; 57; 51]. Some common commercial testbeds running CoAP are InterDigital oneMPOWER, ARM mbed, and thethings.io. IEC 62541 Open Platform Communication Unified Architecture (OPC-UA) is a platform-independent, broker-less, service-oriented architecture that supports pub/sub communication modes for time-sensitive networking and UDP multicast application scenarios. In implementation, the publish and the subscribe servers are successfully decoupled to realize point-to-multipoint transmission [58]. Figure 3: Architecture of a next-generation offshore wind farm data-acquisition system leveraging Industry 4.0 IIoT, Edge, and virtualization technologies using a publish/subscribe model.