There are 4 major Architecture layers In the IoT system

IoT Architecture Layers
Fig. IoT Architecture Layers

In the IoT architecture layer, we start with the bottom layer ie sensor connectivity & network which collects data. Then we have the above layer gateway and network, Management service, and application layer where the collected data are processed according to the needs of different applications. 

Sensor, Connectivity, and Network Layer

This layer comprises RFID tags and sensors. These are wireless devices and form the Wireless Sensor Networks (WSN). Sensors are active in nature so real-time information is to be collected and processed, This layer also has network connectivity (like WAN, PAN, etc.) which is responsible for communicating the raw data to the next layer which is the Gateway and Network Layer. The devices which are comprised of WSN have finite storage capacity, restricted communication bandwidth, and small processing speed. For different applications, we have temperature sensors for collecting temperature data, water quality for examining water quality, moisture sensors for measuring the moisture content of the atmosphere or soil, etc.

sensors connectivity and network layer - iot architecture layers
Figure Sensor, Connectivity, and Network Layer

Gateway and Network Layer 

Gateways are responsible for routing the data coming from the Sensor, Connectivity, and Network layer and passing it to the next layer which is the Management Service Layer. This layer requires having a large storage capacity for storing the huge amount of data collected by the sensors, RFID tags, etc. This layer also has trustworthiness in terms of public-private & hybrid networks. Different IoT device works on different kinds of network protocols. All these protocols are incorporated into a single layer. This layer is responsible for integrating various network protocols.

We have the gateway which is from the embedded OS, Signal Processors, Modulators, Micro-Controllers, etc. Above the gateway we have the Gateway Networks which are LAN(Local Area Network), WAN(Wide Area Network), etc. 

gateway and network layer - iot architecture layers
Fig. Gateway and Network Layer 

Management Service Layer 

The main function of the Management service layer is to manage, the IoT service. This layer is responsible for securing the analysis of IoT devices, Analysis of Information (Stream Analytics, Data Analytics), and Device Management. 

In this layer, data management is required to extract the necessary information from the huge amount of raw data collected by the sensor devices to allow a valuable result of all the data collected and also require an immediate response to the situation. This layer helps for abstracting data, extracting information, and running the data flow. This layer is also responsible for data mining, text mining, service analytics, etc

In the below fig, we have the management service layer as Operational Support Service (OSS) which includes Device Modeling. Device Configuration and Manage and many more. Also, we have the Billing Support System (BSS) which supports billing and reporting and Iot/M2M Application Services which includes Analytics Platform, Data-which is the most important part; Security which includes Acces Controls, Encryption, identity Access Management, etc.: and then we have the Business Rule Management (BRM) and Business Process Management (BPM)

management service layer - iot architecture layers
Fig.Management Service Layer

Application Layer

The topmost layer is the application layer. This layer is responsible for the effective utilization of the data collected. Various IoT applications include Home Automation, E-health, E-Government, etc. In the below fig, we can see that there are two types of applications Horizontal Market which includes Fleet Management, Supply Chain, etc., and Sector-wise application of IoT which has energy, healthcare, transportation, etc.

application layer - iot architecture layers
Fig. Application Layer