object(s)/network(s). So, in case of a bug in the system, there may be a change or collapse of the entire system. Day-by-day IoT technology dominates human lifestyle and thereby increases dependability on IoT technology altogether.
1.2 Technological Evolution Toward IoT
After passing several decades of invention of an electronic device computer, in the 1960s, a communication between two computers was made possible using a computer network. Functioning of the internet commenced after the invention of TCP/IP in the 1980s. Later on, in 1991, the internet became more popular using available WWW. After the invention of www, e-mail, information sharing, and entertainment were introduced on the internet. Interconnectivity of different objects (devices) evolved over the years, and it became the base for technological evolution toward IoT. Web applications became prevalent with evolved network technology resulting in an internetworked ATM. E-commerce was also introduced during this time.
Till 2000, Information and Communication Technology (ICT) provided service related to “anytime”, “anywhere” paradigms. It means it provides service connectivity through the internet any time at any place. But in 2000, we witnessed a new era of ubiquity that suggests a new paradigm of connecting “anything” IoT [20]. Mobile internet technology was also formed parallel to evolution on IoT from 2000 to 2010. Due to the invention of mobile internet technology, social networking platforms such as Skype (2003), Facebook (2004), Twitter (2006), and WhatsApp (2009) were also introduced and thereby the users are getting connected via the internet through connecting devices [3, 4].
As shown in Figure 1.2, IoT technology was infant in 2000, and it has matured during the decade that dealt with other pioneering technologies such as RFID, WSN, and M2M communication that underwent revolution in the product automation industries and service industries. After having M2M communication, IoT which is a network of objects, that communicates with each other via different technologies such as Internet, RFID, GPRS, computers, actuators, and mobile phones without or minimal intervention of human beings. The voyage of IoT technology has been continuing in the path of IoT application domain such as Digital Locker, Smart Healthcare, Smart Vehicle, and Smart Cities. Recently, IoT technology emphasizes Smart Dust (a smaller computer than a grain of sand) collaboration with evolved nanotechnology to diagnose problems in the object system or human society.
Figure 1.2 Evolution of IoT.
Thus, the IoT is a paradigm shift in the Internet technology that is rapidly developing by the advancements in other enabling technologies such as sensor networks, mobile devices, wireless communications, networking, and cloud technologies that results into Industrial IoT (IIoT), an application of IoT in industries. So, now, we will discuss those associated technologies which bring such technological revolution in association with IoT.
1.3 IoT-Associated Technology
In Inter-networked of Things, stake holding technologies expect trillions of Sensors, billions of Smart Systems, and millions of applications in near future. There are numerous supportive technologies with IoT to perform smarter than before. IoT Associative Technology can be classified into four sub-topics, namely,
(i) Sensor and Actuators,
(ii) IoT Networking,
(iii) IoT Connectivity Technologies, and
(iv) IoT Communication Protocol.
(i) Sensor and Actuators: Sensor and Actuators are the most essential and core components of the IoT. As per oxford dictionary, the meaning of sensor is “It is a device which detects or measures a physical property and records, indicates or otherwise responds to it.” [31]. So, sensors basically sense the physical observable fact around us from an environment. As per the other sources [32], sensors can be defined as “A sensor detects (senses) changes in the ambient conditions or in the state of another device or a system, and forwards or passes this information in a certain manner”. According to this definition, a sensor can sense or detect the physical phenomena or measured properties such as temperature, humidity, smoke detection, and obstacle detection. So, we have different specific sensors that can be used to sense particular properties and cannot be used to sense or to detect, or be insensitive to the other properties surrounding us, i.e., specific physical properties can only be detected by specific sensors not bothering about other properties surrounding us. For example, a temperature sensor can sense heat (temperature) around us and then these sensed values are converted into its equivalent electrical signals.The smallest change that can be detected and can be measured by a sensor as an output is known as resolution. Based on the output, the sensor can be classified into two categories: Digital Sensor and Analog Sensor. Analog Sensor can generate or produce a continuous output signal equivalent to continuous measured property in nature; e.g., temperature, humidity, pressure, and speed are analog quantities. While Digital Sensor produces binary output (0 or 1, ON or OFF) signal. So, it generates a non-continuous (discrete) value in the form of bits that combine to gather generated byte as an output. Based on the output data types, sensors can be classified into two major groups: Scalar Sensor and Vector Sensor. Scalar Sensor generates output proportional to quantity measured from surroundings without considering its orientation or direction, e.g., physical quantity such as temperature and pressure. Vector Sensor generates the output that is proportional to quantity measured as well as its orientation or direction, e.g., physical quantities such as sound and velocity.Based on sensed information from sensors, actuators basically perform some actions (actuates) on the physical environment. So, here, actuators take actions based on what has been sensed and in that way controls a system that can be acted upon an environment. In this context, the actuators require some control signal and source of energy to function further. So, when actuators receive such control signals, they convert the energy into mechanical motion. Based on their functional domains, we have three broad categories of actuators such as pressure-based actuators (hydraulic and pneumatic), electric-based actuators (electrical, thermal, and magnetic), and mechanical-based actuators. Other than these types of actuators, other popular actuators are used in industries. Agriculture uses Soft actuators. Soft actuators are polymer-based actuators designed to handle delicate objects and used in robotics.“Transducer” is another associative term which can be used for both Sensors and Actuators [33]. So, actuators sense the surroundings in the form of information and are converted into electrical signals; such control signals are received by actuators and action is taken accordingly. For example, in “soil moisture and water level monitoring application”, agriculture soil water/moisture level in a farm is sensed by specific sensors, is converted into electrical signal, and is provided to the actuator as “solenoid valve”. Solenoid valves consist of a mechanism that allows or stops the water flow. So, depending on the electrical signal received from the sensor (water/moisture level), this solenoid valve as an actuator can actuate, i.e., flow water or stop water.
(ii) IoT Networking: IoT Network consists of several components such as Device (The Thing), Local Network, Internet, Backend services, and Applications. Here, in case of “Device”, it consists of a collection of sensors and actuators that can act as one component in the entire IoT Network. These become different nodes in the IoT Network that can be communicated with each other. As shown in Figure 1.3, a node in IoT Network can be communicated with other target node via another component of IoT network, i.e., Local Network. If target node does not belong to the local network, IoT network will search it through another component of IoT network, i.e., Internet. In Backend services, the data may be received from local networks or from the internet and perform complex analysis using different machine learning algorithms.Such result generated after complex analysis is given to applications that serve as an output
