Among the following layers, identify the one which is used for wireless connection in IoT devices :

Correct — option (3), Network Layer.

The basic model of an Internet of Things (IoT) system has three layers: perception, network and application. A 2020 comparative study of IoT architectures (dos Santos and others), which compares models of three to seven layers, describes it this way.

The perception layer holds the things: sensors that take in information and actuators that act on the environment. The network layer connects each thing with other things, network devices and servers. The application layer delivers services to the end user.

A wireless link connects a device to the rest of the system, so it belongs to the Network Layer. Wi-Fi, Bluetooth, ZigBee, LoRaWAN and cellular networks are examples of technologies used for that connection.

The idea to remember: perception senses, network connects, application serves.

Why the others are wrong

• (1)
  Application Layer — The application layer is where IoT data becomes a service — a smart-home app, a farm dashboard, a city monitoring system. It uses the data that has already arrived; it does not make the wireless link.

  It is the answer when a question asks which layer delivers services to the end user.

• (2)
  Perception Layer — The perception layer is the sensing layer: sensors collect information and actuators act on the environment. It produces the data that the wireless connection then carries.

  It is the answer when a question asks which layer senses or collects data in an IoT system.

• (4)
  Transport Layer — Transport Layer is not one of the three IoT layers. In the TCP/IP and OSI networking models it handles end-to-end delivery between programs, with protocols such as TCP and UDP, not the radio link itself.

  Some five-layer IoT models do name a transport layer for moving data from things to a processing layer. In the three-layer model, whose names match options (1) to (3), the connecting role belongs to the network layer.

The Internet of Things is a network of physical objects fitted with sensors, software and connectivity, so that they can collect and exchange data.

Layered models describe an IoT system by the job each part does. In the three-layer model, the perception layer senses, the network layer carries data between things, network devices and servers, and the application layer turns the data into services.

Richer models split these jobs further. The five-layer model adds a processing layer and a business layer, and uses a transport layer to move data between the things and the processing layer.

Key facts

• The three-layer IoT model has a perception layer, a network layer and an application layer.
• Perception layer: sensors that take in information and actuators that act on the environment.
• Network layer: connects things with other things, network devices and servers, using technologies such as Wi-Fi, Bluetooth, ZigBee, LoRaWAN and cellular networks.
• Application layer: delivers services to the end user, such as smart-home, smart-farming or smart-city applications.
• The five-layer IoT model adds processing and business layers, with a transport layer moving data between things and the processing layer.

Common traps

• 'Transport layer' means different things in different models: end-to-end delivery (TCP, UDP) in TCP/IP and OSI, and data transfer to a processing layer in some five-layer IoT models. Read the other layer names in the options to see which model applies.
• Sensors produce data but do not carry it. Collecting data is the perception layer's job; the wireless link that carries it is the network layer's.
• Vendor IoT architectures can call the connecting layer a 'gateway': the 2020 comparative study found that term, or a similar one, in five of the seven industrial architectures it examined. The word also names devices that process data for a group of devices, so judge a component by what it does, not by its name.

UnlockIAS will link similar questions from RAS Pre 2018 here once that paper is published on this site.

• practice — not a real PYQ

  In the three-layer architecture of the Internet of Things, sensors and actuators belong to the –

  • (a)Application Layer
  • (b)Network Layer
  • (c)Perception Layer
  • (d)Session Layer
  Answer(3) — The perception layer holds the things with their sensors and actuators. Option (1) delivers services to users, option (2) connects devices to servers, and option (4) is an OSI layer name, not an IoT layer.
• practice — not a real PYQ

  Match the IoT layer with its function : A. Perception Layer – i. Delivers services to the end user B. Network Layer – ii. Senses information through sensors C. Application Layer – iii. Connects things with other devices and servers Codes :

  • (a)A-ii, B-iii, C-i
  • (b)A-i, B-ii, C-iii
  • (c)A-iii, B-i, C-ii
  • (d)A-ii, B-i, C-iii
  Answer(1) — Perception senses (A-ii), network connects (B-iii), application serves users (C-i). Options (2) and (3) get every pair wrong, and option (4) swaps the network and application layers.