IoT Middleware Platforms for Smart Energy Systems: An Empirical Expert Survey
2.1. Semantic Interoperability and Data Models
2.2. IoT Platform Definition and Architecture
- Business Layer: It offers a management and control of the IoT platform functions, including data analysis, (e.g., using Apache Spark  in case of dealing with big data) to help in the process of the decision-making by the responsible people.
- User/Application Layer: It is responsible for delivering and presenting the application-specific service to the end user. It defines a wide range of applications where the IoT platforms can be used, such as smart services applications.
- Middleware Layer: The concept of linking billions of individual devices and getting them to communicate with each other means that IoT systems are already inherently characterized by a high degree of heterogeneity . The large number of different communication protocols, interfaces and platforms lead to heterogeneous IoT networks, which complicate the interaction.The task of middleware here is to function as a mediator between the devices by integrating the received data from the physical environment to the IoT-connected devices, networks and servers. This integration process also includes all the necessary operations, such as storing, analyzing and processing the data, allowing the connectivity between different and complex programs, which were not originally designed to provide this feature. Various protocols are used to provide the communication and services to the application in this layer. These protocols correspond to the application layer protocols in OSI model , such as:
- The Hypertext Transfer Protocol (HTTP) : This has been the foundation for data communication for the World Wide Web (i.e., Internet) since 1990 . HTTP is a Transmission Control Protocol (TCP)/Internet Protocol (IP)-based, application-level protocol for distributed, collaborative hypermedia information systems. It is used to deliver data (HTML files, image files, query results, etc.) on the Internet, supporting both request/response and client/server interaction modes.
- The Constrained Application Protocol (CoAP) : An upgraded version of HTTP, designed for the resource constrained applications such as IoT, wireless sensor networks (WSNs) and machine to machine (M2M) communication. One reason for the CoAP’s reduced complexity is the use of User Diagram Protocol (UDP) instead of TCP in HTTP, with acknowledgment messages in order to introduce a reliable communication based on a request/response interaction.
- Message Queuing Telemetry Transport (MQTT) : A protocol that enables a publish/subscribe messaging communication mode in a lightweight way. It is useful for connections with remote locations, where the bandwidth is limited. It was originally designed for TCP/IP network, but other extensions such as MQTT-SN support UDP, ZigBee, etc.
- OPC Unified Architecture (OPC UA) : It is a service-oriented, technology-independent and platform-independent approach. It has created new and easy possibilities for communicating with Linux/Unix systems or embedded controls on other platforms and for implementing OPC connections over the Internet supporting both TCP and UDP. The fundamental element in OPC UA is the use of information modeling framework that turns data into information based on rules and building blocks necessary to expose an information model, and this imposed the different data models, which are described in Section 2.1. The communication in OPC UA uses the client/server and publish/subscribe (PubSub) schemes.
- Extensible Messaging and Presence Protocol (XMPP) : An open XML technology for real-time communication, which powers a wide range of applications, including instant messaging, presence and collaboration using the point/point interaction over TCP transport. The name of this protocol presents its main features and functionalities as: X (eXtensible): defines that the technology is designed to be extensible and an open system; M (Messaging): describes the exchanged instant messages (IM) between clients, and which happens in real-time using a push mechanism to avoid increasing unnecessary network loads; P (Presence): determines the state of an XMPP entity as online, offline, busy, etc.; P (Protocol): expresses it as a set of standards that allows systems to talk to each other.
- Advanced Message Queuing Protocol (AMQP): An open standard for passing business messages between applications or organizations using TCP. It connects systems, feeds business processes with the information they need and reliably transmits onward the instructions that achieve their goals using the point/point and publish/subscribe interaction modes . It was designed to achieve main goals of: message orientation; queuing; routing; security; reliability; interoperability.
- Data Distribution Service (DDS) : A middleware, M2M, Object Management Group (OMG) protocol and API standard for data-centric connectivity. It integrates the components of a system, providing low-latency data connectivity, high reliability and high scalability in publish/subscribe and request/response patterns over TCP and UDP.
- Network Layer: It is also known as the transport layer; it is responsible for transporting the data provided by the perception layer to the application layer. It uses an enormous number of standards and protocols to enable this connection, such as:
- IP version 6 (IPv6) : This has been designed to be an evolutionary step from IP version 4 (IPv4). The changes from IPv4 to IPv6 fall into the these main categories: expanded addressing capabilities; header format simplification; improved support for extensions and options; flow labeling capability; authentication and privacy capabilities.
- ZigBee : A low data rate, low-power-consumption, low cost, wireless networking protocol, to target automation and remote control applications. ZigBee’s best quality is its low-power-consumption that can allow batteries in devices using ZigBee to last for several years. The main advantages of ZigBee over Z-Wave are the higher data rate and the ability to connect an unlimited number of nodes together.
- Z-Wave [62,63]: A wireless protocol evolved by Zensys and confirmed by the Z-Wave Alliance for automation devices for homes and commercial environments. It enables reliable transmission of short messages from the control unit to one or more devices in the network with the minimum noise, low-power-consumption (less than ZigBee) and long battery life. It also operates at a low frequency range (800–900 MHz), which means a less congested band and covers a larger range of data transmission. On the other hand, in comparison with ZigBee, Z-Wave allows connecting a limited number of nodes, with lower data rates.
- Bluetooth : A wireless technology standard that is used for exchanging data between fixed and mobile devices over short distances using Ultra High Frequency (UHF) radio waves and building personal area networks (PANs) instead of wire connections. In the most widely used mode, transmission power is limited to 2.5 milliwatts, giving it a very short range of up to 10 m (30 feet).
- WiFi : It (also called 802.11) was released in 1997. It is a wireless technology that transmits data using high frequencies over short ranges (100 m/300 feet outdoors and 50 m/150 feet indoors). WiFi has different types based on the chosen frequency and transmission rate, such as 802.11a, 802.11b, 802.11g and 802.11n. The main limitations of WiFi include its susceptibility to interference from devices that use the same frequency band such as Bluetooth devices, in addition to the impact of obstructions on its signal path, which may lock the signal in some cases.
- 4G/Long Term Evolution (LTE) : Telecommunication networks are classified into generations based on speed, connectivity and reliability standards set by the International Telecommunications Union-Radio communications sector (ITU-R). 4G is the 4th generation of communication services. It was developed in 2009 after the two older generations 2G and 3G. It has slowly replaced 3G, since it is about 10 times faster than 3G. It also provides more capacity than older generations, and thus larger bandwidth. LTE is the technology behind 4G, and it was designed at the same time as some other standards, such as the UMB (Ultra Mobile Broadband) and the Worldwide Interoperability for Microwave Access (WiMax). LTE is the global standard technology for cellular communications. It is an open, interoperable standard used by virtually all carriers. It provides mobile and broadband data, telephone service with high speed and supports public safety functions as well.
- 5G : The 5th generation mobile network is a wireless standard which was designed after 4G networks. 5G networks connects virtually everyone and everything, including machines, objects and devices. The main advantage of the 5G wireless technology is meant to deliver higher multi-Gbps peak data speeds, ultra low latency, more reliability, higher network capacity and more availability than any previous mobile network technologies.
- LoRAWAN: One of the low-power wide area networking (LPWAN) technologies. It is a wireless networking protocol which uses the LoRa radio modulation technique layer. It features low-power operation (around 10 years of battery lifetime), a low data rate and a long communication range. It was developed by Cycleo, a French company acquired by Semtech .
- Low-Power Personal Wireless Area Networks (6LoWPAN): A developing standard from the Internet Engineering Task Force (IETF) 6LoWPAN Working Group. It was designed from the start to be used in small/pico sensor networks . This type of wireless sensor network sends data as packets using IPv6—and here is where the name comes from—over Low-Power Personal Wireless Area Networks.
- Long-term evolution machine (LTE-M) : An LPWAN technology (also called LTE-MTC or LTE Cat M) which allows the reuse of an LTE installed base with extended coverage. LTE M, which stands for LTE-Machine Type Communication (MTC), is also a LPWAN technology developed by 3GPP to enable devices and services specifically for IoT applications.
- Narrow Band Iot (NB-IoT) : An LPWAN radio technology deployed over mobile networks which is especially suited for indoor coverage, low cost, long battery life and a large number of devices.
- Perception layer: Physical/device layer, which includes all the passive, semi-passive and active hardware needed for gathering information from the environment, or taking actions in the physical system, such as sensors, actuators and other physical devices.
2.3. Non-Functional Requirements and Challenges of IoT Platforms
- Interoperability: Different components of the IoT system must be able to connect and contact to each other. Historically, the building automation domain has always had interoperability issues, especially due to the segmented building process, leading to contractors offering trade-specific devices which are often incapable of communicating with devices from other trades. According to the economic research, up to 60% of the value that IoT systems might reveal is now locked by a lack of interoperability. Considering this, the IoT offers a great chance to actually improve interoperability by integrating and standardizing different components within the IoT platform .The interoperability challenge combines three elements:
- Device and connectivity: the starting point of the IoT architecture, which includes device capabilities and protocols.
- Data: several problems may arise when trying to combine data from different sources for different needs.
- Services/applications: these problems occur in the case of using data generated by a specific IoT device, in another application.
- Scalability: Device scalability defines its ability to adapt to the new changes in the environment, which is an essential feature for the growing IoT systems. Reliable IoT middleware needs to provide similar functionalities and similar quality of service (QoS) in small-scale and in large-scale environments .
- Flexibility and Openness : Any IoT system needs to be flexible enough to support future technologies. Manufacturers typically create specialized hardware which gives optimal performance, while on the other hand, limiting the hardware’s ability to track new updates and features. This introduces one of the most challenging problems for the IoT frameworks: vendor locking. Hence, a balance between software features and specialized hardware capabilities is one approach that must be considered in order to achieve the necessary flexibility of the system. The need for hardware-independence introduces the need for open IoT platforms, open standards, open APIs and open data. In particular, openness in smart cities and buildings services is critical, since such systems usually include humans, which in turn increases the importance of having a flexible, resilient and open platforms, which allows all possible users actions such as the data exchange.
- Energy Efficiency : Energy conservation and consumption is one of the major challenges to be addressed by IoT systems, especially in smart cities where the devices are used everywhere in the environment and closely to the nature and to the humans. Accordingly, the energy challenge of the IoT platforms includes: battery lifetime and power consumption of the sensors and devices which depend on the sensing time; bandwidth/data range/throughput/latency; and the application range. Possible solutions include using the suitable communication technologies that are convenient for the needed covered range by the IoT application, such as using the Low-Power Local Networks for the short-range solutions and the Low-Power Wide Area Networks for communications that exceed 1000 m.
- Security [73,75]: Since a large number of “things” are connected together in one heterogeneous system, the security feature is fundamental in any system and includes all the different components. Thus, the system must be robust enough to deal with any of the possible security attacks by: firstly being able to detect the attack; then diagnosing the attack; and eventually deploying countermeasures and repairs. Considering an open, flexible, low power, lightweight platform makes providing the needed heavyweight security computations critical for future researches.
- Privacy : Human interaction, data exchange and wireless communication through the middleware platforms provide good functionalities, but also create a high possibility of violating privacy. Privacy solutions have been addressed by many works, offering secured authorization and authentication mechanisms for the users to access the data sources, e.g., the sensors and the data, in addition to encrypting the transmitted data during the communication.
3. Literature Review
Middleware Platforms in Smart Energy Systems
4.1. Presentation of the Results
4.2. Threats to Validity and Limitations of the Study
5.1. Business Layer and End-Users
5.2. NFRs and Challenges
5.4. Middleware Communication Protocols
5.5. Network Communication Standards
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
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|It is important for us to use open source|
IoT Middleware Platforms
|We would participate in the development of|
an open source IoT Middleware Platform
|We would rather pay for a full service|
than administrating on our own
|Avoid vendor locks||5.7||6.0||6.2|
|Providing a GUI||5.7||6.0||5.8|
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Alfalouji, Q.; Schranz, T.; Kümpel, A.; Schraven, M.; Storek, T.; Gross, S.; Monti, A.; Müller, D.; Schweiger, G. IoT Middleware Platforms for Smart Energy Systems: An Empirical Expert Survey. Buildings 2022, 12, 526. https://doi.org/10.3390/buildings12050526
Alfalouji Q, Schranz T, Kümpel A, Schraven M, Storek T, Gross S, Monti A, Müller D, Schweiger G. IoT Middleware Platforms for Smart Energy Systems: An Empirical Expert Survey. Buildings. 2022; 12(5):526. https://doi.org/10.3390/buildings12050526Chicago/Turabian Style
Alfalouji, Qamar, Thomas Schranz, Alexander Kümpel, Markus Schraven, Thomas Storek, Stephan Gross, Antonello Monti, Dirk Müller, and Gerald Schweiger. 2022. "IoT Middleware Platforms for Smart Energy Systems: An Empirical Expert Survey" Buildings 12, no. 5: 526. https://doi.org/10.3390/buildings12050526