IoT system design principles

It is expected that billions or trillions of IoT devices will be deployed in the various sectors of the society or economy (e.g., intelligent transport systems, smart health care, smart manufacturing, smart homes, smart cities, smart agriculture, and smart energy) to deliver better customer experience, provide more value to the market, and to solve significant problems such as climate change, national security, and public safety. Integrating massive numbers of IoT nodes, networking nodes, and computing devices or applications into the existing infrastructures in various industries will increase their complexity. It is, therefore, essential to follow some design principles to ensure that IoT systems designed to solve problems or create unique value in the various industries are adequately designed to fulfill their intended functions and are easier to operate, maintain, and scale.

IoT system design has its own set of challenges as IoT systems often contain multiple components or elements (e.g., sensors and actuator cyber-physical devices, networking nodes, computing nodes) interacting with one another to collect data, manipulate physical systems, transport data packets, and analyse the collected data to deliver better customer experience, create value, or solve a specific problem. Below are some effective IoT system design principles that should considered when designing IoT systems

Before designing IoT systems, it is essential to understand the problems or challenges the customers face before attempting to design an IoT solution to address them. The designer must think from the perspective of customers and then design a research study to understand the customer's problems and the existing solutions they have and then find out how IoT solutions can address those challenges. It is only after understanding the actual problem that the customers are facing and how IoT solutions could address them that IoT system designers should engage in developing a solution to address them.

An IoT system may be designed not only to solve a problem or pain that potential customers are feeling but could be designed to create unique value. Innovative IoT solutions could create unique value to make their potential customers productive and competitive. It is required that IoT system designers understand the unique value that their system or solution is going to offer to their potential customers to improve their productivity, competitive advantage, or user experience. It is, therefore, required to conduct proper research before engaging in the project.

The research process could include defining research questions, defining the market segment, sending out questionnaires to potential customers, conducting interviews with relative stakeholders in the target market, talking with sales representatives of potential customers, and attending industry conferences. The research findings should be well documented and analysed by all the stakeholders and the design team before the IoT project is launched so that the designers can cater to the customers' needs during the design process.

The features to be included in the IoT solution should align with users' needs and problems and the value they can derive from the products to improve their productivity, competitive advantage or experience. The users are sometimes unaware of the value of IoT solutions or how they could address some of their problems, making them reluctant to adopt IoT solutions. Another barrier preventing users from adopting IoT solutions is uncertainties regarding cost, usability, returns on investments, and security concerns. Thus, it is the design team's responsibility to address those user concerns when designing IoT solutions.

It is essential to answer the following questions:

• What value will be delivered to the users by the IoT solution to be designed?
• What are some of the barriers that will prevent users from adopting the IoT solution to be designed?
• How will the IoT solution be designed to address the users' needs, problems and challenges?
• How will the IoT solution be designed to deal with the user adoption barriers?
• Which features are to be added to the IoT solution to be designed, and will they address the problems of users and deliver the value that will improve their productivity, competitive advantage, and quality of experience?

It is essential to address the above questions carefully during the research stage and during the technical design stage. Thus, when designing IoT systems, it is essential to focus on the values, needs, and problems of the user.

The Internet of Things (IoT) is still in its early stages. We still have the opportunity to ensure that IoT systems are scalable, energy efficient, cheap, and secure by design while providing acceptable QoS. Another design requirement for IoT systems is interoperability. A holistic system-based approach is required to attain all these design goals and the goals of other stakeholders (network operators, service providers, regulators, and end users). There is a need for the development of formal methods and tools and methods for the design, operation, and maintenance of IoT systems, networks, and applications in such a way as to satisfy the goals of the various stakeholders with minimal unintended consequences.

An IoT system often consists of multiple elements, such as the cyber-physical system (sensors and actuator device) deployed to collect data from the environment and to manipulate physical systems, communication systems deployed to transport data within the IoT infrastructure, and computing systems deployed to process the massive of data collected by the sensor and send feedback to actuators to automate physical processes or to human operators to make some decisions (or take some actions). One of the elements of the IoT infrastructure is the cyber security system, which should interact with other systems within the IoT infrastructure to deliver the required service. Sometimes, the IoT system is designed to interact with other systems to deliver a specific value or solve a specific problem. It is, therefore, important to adopt a system-based approach when designing IoT systems to ensure that the interaction between the various IoT elements and other existing systems of the organisation or users delivers the expected value or addresses the problems they are designed to solve. System thinking, design thinking, and systems engineering methods and tools can be leveraged to develop formal tools for designing IoT systems.

Users are concerned about possible security weaknesses that could be created in their infrastructure after integrating IoT solutions. IoT system designers should incorporate security mechanisms into their solutions to address the users' security concerns. Sometimes, IoT system designers are preoccupied with implementing features that are required to address the problem of customers or deliver the expected value to customers that they may ignore the implementation of features that address the security concerns of customers. Some IoT device manufacturers and service providers are often preoccupied with minimising manufacturing and deployment costs and the “time-to-market” such that security concerns are ignored or considered later.

Securing the data and the hardware and software assets of an IoT infrastructure is essential and should be considered when designing IoT infrastructures. IoT system designers should consider a robust cyber security system as a subsystem within the IoT system to be designed and how the cyber security system will interact with other subsystems to deliver a secured IoT solution to the users. The IoT cyber security system consists of multiple elements that work together to provide an effective security solution to protect the data and other IT assets within an IoT infrastructure. Some of the cyber security features that should be considered when designing IoT solutions include:

• Cryptography: Encryption
• Access control
• Attack detection and prevention
• Honeypots
• Runtime monitoring
• Firewalls

A major security weakness in IoT infrastructures is often at the IoT device level. Because the batteries used to power these devices have a limited energy capacity, their computing and communication capabilities are very limited, making it difficult to implement reliable but sophisticated security mechanisms. As a result, it is easy to compromise these devices to disrupt IoT services and sometimes turn them into an army of botnets to conduct massive and sophisticated distributed denial of service attacks on the IoT infrastructure as a whole and the Internet. Maintaining a rational trade-off between performance, energy consumption, and security is essential.

The IoT security threats to be considered during IoT system design are not only those from external attackers but also those from internal attackers. The threats could be within, and there should be a mechanism to deal with internal threats. The internal threats could be from disgruntled employees (users) and reckless or careless ones who may perform operations that may breach or compromise some of the IT assets within the IoT infrastructures. Therefore, the IoT system designer must understand every possible error that may occur when operating IoT systems and then take care of them when designing the IoT solution and ensure that the users are aware of such errors and well-equipped to handle them.

The security aspects to be considered when designing IoT systems are not only cyber security aspects but also the physical security aspects. The physical security of the IoT infrastructure should be considered when designing and deploying them. Some adequate measures should be designed to address threats to the physical security of IoT devices.

Energy and environmental sustainability are among the essential constraints to consider when designing and deploying IoT infrastructures. Since IoT devices are designed to be small, light, and powered by small batteries with limited energy capacity, energy efficiency is a primary design criterion when designing IoT devices. In order to reduce the energy consumption of IoT devices to a minimum level, low-power communication and networking technologies, low-power computing hardware and software, and low-power security mechanisms are incorporated into IoT devices. As the amount of data collected by the IoT devices from the environment increases, the traffic transported through the networking infrastructure to edge/fog/cloud computing nodes or data centers increases, increasing energy consumed for data communication and computing purposes. The increase in energy consumed by IoT infrastructures increases the carbon emission from the IoT industry which increase sharply with the rapid increase in the large scale adoption of IoT in the various sectors of the economy.

In addition to energy efficiency, it is essential to minimise the amount of waste the IoT industry creates. IoT devices are powered by batteries with very limited energy capacity, resulting in a very short lifetime for IoT devices (the lifetime of an IoT device is the time to deplete all the energy stored in the battery of the IoT, requiring a recharge or change of battery). If the IoT batteries are replaced within a very short time (less than a decade), then with the deployment of tens of billions or trillions of IoT devices globally, there will be a problem of how to dispose or recycle the IoT batteries. There is already an environmental problem in managing the massive amount of batteries and e-waste the electronics industry generates. The problem will worsen if environmental sustainability is not considered as one of the design criteria when designing IoT devices. Some of the green and environmental sustainability strategies that should be considered when designing IoT devices include:

• Green IoT hardware: Designing energy-efficient IoT hardware and incorporating hardware-based energy-saving mechanisms in IoT devices (e.g., shutting down idle devices).
• Green IoT communication infrastructure: Designing energy-efficient networking and communication infrastructure and adopting low-power networking and communication technologies for IoT networks.
• Green IoT architectures: Adopting energy-efficient networking, communication, and communicating architectures. For example, adopting edge/fog computing-based architectures where lightweight processing is shifted from the cloud data centres (often located far away from the IoT devices) to energy-efficient edge/fog computing nodes (closer to the IoT nodes). This kind of architecture improves the performance (decreases the packet delays and packet losses). Also, it increases energy efficiency as it decreases the energy consumed in transporting IoT packets through core networks to cloud data centres and reduces the computing demand of the cloud data centres, reducing their energy demand. The edge/fog nodes are sometimes energy-efficient (low-power) computing devices like Raspberry Pi.
• Green IoT software: Designing energy-efficient software and algorithms for processing IoT data and IoT security mechanisms.
• Green energy sources for IoT systems: Energy harvesters are incorporated into IoT devices to harvest energy from the environment to charge the energy storage systems (battery or capacitor/supercapacitor/ultracapacitor), which supplies the IoT device when the renewable sources are not able to generate a sufficient amount of energy to power the IoT devices directly. Using renewable energy sources also increases the lifetime of the IoT devices, decreasing the maintenance cost of changing the IoT batteries or capacitors/supercapacitors/ultracapacitors and minimising the amount of waste generated from the IoT industry.
• Green IoT policies: Policymakers should also develop green IoT regulations and standards to be followed when designing green and sustainable IoT solutions.
• Green IoT education: There should be an education strategy to raise public awareness of the need for green and sustainable IoT solutions so that IoT users, developers and service providers should consider environmental sustainability when making their choices.

When designing IoT solutions, it is essential to consider the physical, social, and environmental context in which the device will be used. The features and specifications when designing IoT devices depend on the application context. The IoT systems designed for small agriculture, smart cities, smart health care, smart homes, intelligent transport systems, Internet of military things (Military Internet of Things (MIoT) or Battlespace Internet of Things (BIoT)), or smart energy should take into consideration the physical or social realities that may impact the integration of IoT systems into a given sector to fulfil a defined goal or purpose. For example, IoT devices designed for agricultural, disaster/emergency response, or battlefield purposes should operate sustainably in harsh conditions that may differ from IoT devices designed for smart homes or medical or health care purposes.

In order to consider the application context, it is recommended to treat the entire IoT use case as a system of which the IoT system being designed is part. In this way, the interaction between the IoT system being designed and other existing systems in the sector (e.g., cities, homes, factories, transportation infrastructure, health care infrastructures, etc.) are modelled using system engineering or systems dynamics modelling tools to ensure that the system to which the IoT system being designed is part of functions as a whole. Integrating IoT systems into existing systems in the infrastructure of an organisation may create new problems that did not exist or may not provide the intended benefit to the organisation. Hence, it is essential to consider the application context and apply a system-based approach when designing IoT systems or solutions.