Logical Design of Internet of Things | IoT Tutorials

Logical Design of IoT – The logical design of an IoT system refers to an abstract representation of entities and processes without going into the low-level specifics of implementation. It uses Functional Blocks, Communication Models, and Communication APIs to design the Logic and implement an IoT system.

A Logical design of IoT consists of the following elements:

1. IoT Functional Blocks
2. IoT Communication Models
3. IoT Communication APIs

IoT Functional Blocks

An IoT system consists of several functional blocks, like Devices, services, communication, security, and applications that provide the capability for sensing, actuation, identification, communication, and management.

These functional blocks consist of devices that provide monitoring control functions, handle communication between host and server, manage the transfer of data, secure the system using authentication and other functions, and interface to control and monitor various terms.

• Application – It is an interface that provides a control system that is used by users to view the status and analyze of system.
• Management – This functional block provides various functions that are used to manage an IoT system.
• Services – This functional block provides some services like monitoring and controlling a device, publishing and deleting data, and restoring the system.
• Communication – This block handles the communication between the client and the cloud-based server and sends/receives the data using protocols.
• Security – This block is used to secure an IoT system using some functions like authorisation, data security, authentication, 2-step verification, etc.
• Device – These devices are used to provide sensing and monitoring control functions that collect data from the outer environment.

IoT Communication Models

There are several different types of models available in an IoT system that are used to communicate between the system and server, like the request-response model, publish-subscribe model, push-pull model, exclusive pair model, etc.

Request-Response Communication Model

This model is a communication model in which a client sends a request for data to the server and the server responds according to the request. When a server receives a request, it fetches the data, retrieves the resources and prepares the response, and then sends the data back to the client.

In simple terms, we can say that in the request-response model, the server sends the response equivalent to the request of the client. In this model, HTTP works as a request-response protocol between a client and server.

Example – When we search a query on a browser, the browser submits an HTTP request to the server, and then the server returns a response to the browser(client).

Publish-Subscribe Communication Model

In this communication model, we have a broker between the publisher and the consumer. here publishers are the source of data, but they are not aware of consumers. They send the data managed by the brokers, and when a consumer subscribes to a topic that is managed by the broker, and when the broker receives data from the publisher, it sends the data to all the subscribed consumers.

Example – On the website, many times we subscribed to their newsletters using our email address. These email addresses are managed by some third-party services, and when a new article is published on the website. It is directly sent to the broker, and then the broker sends the new data or posts to all the subscribers.

Push-Pull Communication Model

It is a communication model in which the data is pushed by the producers into a queue, and the consumers pull the data from the queue. Here, producers are not aware of the consumers. 

Example – When we visit a website, we see a number of posts that are published in a queue, and according to our requirements, we click on a post and start reading it.

Exclusive Pair Communication Model

It is a bidirectional, fully duplex communication model that uses a persistent connection between the client and server. First, set up a connection between the client and the server and keep it open until the client sends a close connection request to the server.

IoT communication APIs

These APIs, like REST and WebSocket, are used to communicate between the server and the system in IoT.

REST-based communication APIs

Representational state transfer(REST) API uses a set of architectural principles that are used to design web services. These APIs focus on the systems’ resources and how resource states are transferred using the request-response communication model. This API uses some architectural constraints.

• Client-server – Here, the client is not aware of the storage of data because it is concerned about the server, and similarly, the server should not be concerned about the user interface because it is a concern of the client. And this separation is needed for the independent development and updating of the server and client. no matter how the client is using the response of the server, and no matter how the server is using the request of the client.
• Stateless – It means each request from the client to the server must contain all the necessary information for the server to understand. Because if the server can’t understand the request of the client, then it can’t fetch the requested data in a proper manner.
• Cacheable – In response, if the cache constraints are given, then a client can reuse that response in a later request. It improves the efficiency and scalability of the system without loading extra data.

A RESTful web API is implemented using HTTP and REST principles.

WebSocket-based communication API

This type of API allows bi-directional full-duplex communication between server and client using the exclusive pair communication model. This API uses full-duplex communication, so it does not require a new connection setup every time it requests new data.

WebSocket API begins with a connection setup between the server and client, and if the WebSocket is supported by the server, then it responds back to the client with a successful response, and after the setup of a connection between the server and the client can send data to each other in full-duplex mode. This type of API reduces the traffic and latency of data and makes sure that each time we request new data, it cannot terminate the request.