Physical and Digital - The Twain shall meet
In the previous posts, we explored about different types of data acquisition. Now, we are transitioning into the next layer in the IIoT anatomy - the Edge. This blog post will provide you a broad overview of the Edge layer by answering the following questions.
What is Edge ?
What does the Edge do?
Why do we need the Edge?
In the subsequent blog posts we will explore the world of edge devices, understand the hardware and software features, edge computing, and define a detailed requirement specification for an Industrial IoT edge device in context of an application.
What is the Edge ?
In IoT parlance, the edge is the layer in which the physical meets the Digital.
As shown in the below diagram, on one side of the edge layer is the Physical (i.e.) Equipment, Sensors, Controllers and on the other side of the edge is the Digital (i.e.) messaging format, protocols, connectivity, data, information.
In the context of Industrial IoT, the Edge is a versatile, industrial grade, intelligent hardware device that acts as an interface between the physical side of Industrial IoT and the Digital side. Generally, IoT gateways are known as the Edge devices, and mostly the Edge devices are located in the physical environment (i.e.) the manufacturing shop floor, machinery, heavy equipment etc.
The terms "Edge" and "Gateway" is used interchangeably in this blog post.
What does the Edge do ?
Given below is an overview of Edge functionalities.
1. Data Acquisition
Acquire raw operational and condition data from industrial assets in real time
Compatibility with different data sources like Analog inputs, Digital inputs, Field protocols like Modbus, CANBUS, Profibus
Augment this data with additional information like GPS location and RTC time stamp (Time stamp from Real Time Clock)
2. Data Processing
Convert the raw data into meaningful information by performing basic mathematical operations and engineering unit conversions
3. Edge Intelligence
Perform analysis on the information. These analysis may range from simple rule based, statistical, to machine learning at the edge. Capability of the edge device to perform complex analysis depends on the hardware footprint and the firmware
Generate insights and alerts based on the analysis
4. Accept remote commands from IoT platform
Accept remote commands from IoT platform to initiate necessary actions in the field
5. Initiate real time actions
Initiate real time actions based on the insights and alerts or based on remote commands from IoT platform
These actions can range from simple notifications to relevant stakeholders to actual actuation and control of equipment and machinery
6. Create information packets
Aggregate and create meaningful packets of information for transmitting to the IoT platform
These information packets can contain asset information, location data, operational data, equipment condition data, insights and alerts
Preferable to have these information packets in a structured format like a JSON (Java Script Object Notification)
7. Manage connectivity
There could be multiple connectivity options available to the gateway to connect to the IoT platform. The most commonly used ones are GSM (Dual SIM, Multi SIM), LTE, WiFi, Wired Ethernet
Gateway device should have the ability to switch between connectivity options based on availability and signal strength. Switching between connectivity options is more applicable to gateways installed in mobile equipment. Switching may not be applicable for environments like a manufacturing shop floor with stable connectivity options
Store and forward – Store data locally in the gateway when connectivity is not available and forward when connectivity is available. This is also more applicable for gateways installed in mobile equipment that operate in locations with patchy connectivity
8. Transfer information packets to IoT platform
9. OTA
Accept, validate, and execute over the air firmware updates and over the air application updates in an error free manner
10. Device Security
Physical access security – Hardware features to detect unauthorized access to the gateway device such as detecting and alerting opening of the gateway enclosure, effective access controls for administrative ports, making the casing and enclosure tamper evident
Hardware root of trust – Secure silicon level trusted execution environment that brings the gateway to a reliable run state with authorized firmware running on the device
Secure boot – Process of executing a boot sequence to ensure that bootloader[5] is not tampered with, authentic firmware is loaded, subsystems and services are functioning properly, and a valid application code is running in the gateway
Certificate based authentication – Gateway should support certificate-based authentication[6] to ensure that only genuine gateway devices are part of the Industrial IoT system
Secure remote updates – Ability to receive and execute signed over the air firmware and software updates sent over encrypted channels
TLS – Transport layer security using encrypted channels for data privacy and data integrity
The functionalities listed above (Functionalities 1 to 10) are akin to a super set of functionalities. All the gateways may not have all these functionalities. There are variants of gateways that have a subset of these functionalities.
Why do we need Edge devices ?
Edge devices (or) Industrial IoT gateways are absolutely vital to any Industrial IoT system due to the following key reasons
Aggregation – IoT gateways aggregate data from different sources (Sensors, Controllers, PLCs, SCADA systems) and create a meaningful data set for any given entity. An entity can range from a single equipment or machinery to a complete assembly line in a manufacturing shop floor
Standardization and Interoperability – IoT gateways handle the variety in the physical side of the system and standardizes the digital side of the system. The variety in the physical side depends on the ability of Industrial assets to provide data to the IoT gateway. A properly designed gateway will have the wherewithal to accept data from a variety of data sources from different types of industrial assets. While the gateway accepts data from a variety of sources, after processing the data the gateway enables standardization with respect to messaging formats and communication protocols to the IoT platform
Sending meaningful information to the IoT platform – In many IIoT applications, gateways collect raw data from multiple data sources at a high sampling rate. Many times, the data points may remain the same or be within acceptable limits. Considering this, it would make sense to send meaningful information to the IoT platform rather than sending all the raw data as is. However, we need gateways with computation capabilities to make this happen
Real time intelligence and actions – Sending all the data to the IoT platform, analyzing, and taking actions based on the analysis creates latency in the system. Gateways with edge computing capabilities can analyze and take actions in real time without depending on the IoT platform
Offline operation – IoT gateways enable the system to be operational even in case of intermittent connectivity.
Now that you have a high level overview about Edge / IoT Gateways, pls read my next blog post to understand the different building blocks of these Edge devices ...
[1] In the context of Industrial IoT, TLS or Transport Layer Security is a cryptographic protocol that enables devices such as IoT gateways to communicate in a secure manner with the IoT platform through the Internet using encryption techniques. When the IoT platform and the gateway are connected through internet, TLS helps in providing data privacy and data integrity. The latest version of TLS is TLS 1.3. [2] MQTT or Message Queuing Telemetry Transport is a lightweight publish – subscribe messaging protocol commonly used in IoT applications [3] Data Distribution Service for real time embedded systems is a publish - subscribe protocol that enables scalable real time messaging for Industrial IoT applications [4] OPC – Unified architecture is an open source M2M communication protocol developed by OPC foundation for Industrial automation applications [5] Program that loads the edge device operating system when the gateway is switched on [6] Usage of a digital certificate and public key cryptography to authenticate genuine edge devices to be part of the IIoT system
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