# IoT Middleware Platforms for Smart Energy Systems: An Empirical Expert Survey
## 3 Literature Review
#### Middleware Platforms in Smart Energy Systems
One of the services Siemens provides is the EnergyIP meter data management (MDM) application, which is currently enabling more than 200 electricity, gas and water utility companies to manage more than 90 million meters. In 2020, a cloud-hosted MDM started to be used, with the support of Amazon Web Services (AWS). The IoT-platform EnergyIP offers a set of tools and features, which address traditional and emerging use cases, such as billing. Additionally, it uses a unified data model and unified information technology (IT) and operational technology (OT) integration, which allow connecting smart meters from different vendors, with secured connectivity via wireless, radio, LAN and power line communication. _Enterbrain S.R.L._[95] is a company that provides solutions for optimizing energy consumption for air conditioning, improving environmental comfort and reducing COemissions and one's carbon footprint. The Enerbrain IoT solution offers remote control of heating, ventilation and air conditioning (HVAC) systems by connecting them to the cloud. The provided solutions include a set of sensors, actuators, controllers, meters, etc., such as eSense, eNode, ePLC and eMeter. The main IoT solution is eGateway, which connects the Enerbrain devices to WiFi or Ethernet (ETH) supporting WiFi-GSM-ETH communications in three different operating modes (from GSM to WiFi, from GSM to ETH, from ETH to WiFi). _FIWARE_[96] provides a curated framework of building blocks for IoT middleware solutions, building upon the standards, ontologies and reference models described by the SAREF ontology and the NGSI specifications suite. The Orion context broker acts as the central entity in the middleware platform and supports communication via HTTP. Data persistence is handled by a MongoDB. These two components constitute the minimal setup required to deploy the platform. The FIWARE framework proposes various well-established open-source software components from other developers for additional functionality. For instance, to connect to IoT devices via other protocols than HTTP, the platform can use a separate module, the IoT agent. The IoT agent supports LightweightM2M over CoAP qne JSON or UltraLight over HTTP/MQTT, OPC-UA, Sigfix and LoRaWAN. To capture spatial-temporal time-series data about the system state, FIWARE proposes the QuantumLeap services in conjunction with a time-series database such as CrateDB or TimescaleDB. The FIWARE project has received a lot of attention in the research community, and there are many examples in the literature of IoT platforms developed within the FIWARE framework, such as [14; 15; 16; 97]. _Microsoft Azure IoT Central_[98] is a commercial cloud-based application platform specifically aimed at enterprise-grade IoT solutions. It provides a webUI to connect, manage and monitor devices and connect them to line-of-business applications. IoT devices' communications are possible via MQTT, MQTT over WebSockets, AMQP, AMQP over WebSockets and HTTPS. High-level services such as visualization, data analysis and data monitoring can be implemented by using pre-defined application templates [99], such as smart meter analytics and solar panel monitoring, or by building custom applications from scratch. _Niota Cross IoT Platform_[100; 101] is an IoT platform for developing and deploying vertical IoT solutions across multiple industries. It combines data from various sources, such as sigfox, NB-IoT, LoRaWAN, M2M and NFC. Niota's IoT platform allows one to integrate new and old features and business models of Industrial Internet of Things (IIoT), within the current IT ecosystem. Additionally, it offers number of advantages, such as supporting different communication technologies; inbound and outbound interfaces; providing a visual IoT service builder; focusing on the integration, interoperability, flexibility and the security of sensitive data.