RFUnderstanding LoRaWAN Class A, B, C: Device Classes and Differences
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LoRa and LoRaWAN devices are classified into three distinct classes: Class A, Class B, and Class C. These classes define how each device communicates within a network and cater to different power consumption and latency requirements. A LoRa network is composed of end devices and gateways. Based on the MAC layer, there are three classes of end devices in a LoRa network: Class A, Class B, and Class C. All LoRa classes-based end devices are bi-directional in nature for communication.
The following sections outline the basic features of these LoRa class types.
LoRaWAN Class A End Devices
Here are the features of LoRa Class A end devices:
- The frame, in general, is divided into uplink and downlink transmissions. The uplink consists of 1 slot followed by 2 downlink slots (or windows).
- The uplink slot is scheduled by the end device itself based on its needs. It’s decided on a random basis, similar to the ALOHA protocol.
- It is the lowest power LoRa end device.
LoRaWAN Class B End Devices
The features of LoRa Class B end devices are:
- This class of end devices uses extra receive windows during the downlink period in addition to the two time slots specified in Class A.
- Class B devices will get extra receive windows at a specified duration.
- The duration is specified by the gateway using a beacon frame.
- Hence, in this way, the LoRa system indicates to the server when the end device can listen.
LoRaWAN Class C End Devices
The features of LoRa Class C end devices are:
- This class of end devices can listen all the time except in transmit mode. Hence, it is ideal for applications requiring more downlink transmissions.
- Class C LoRa end devices will utilize more power compared to Class A and Class B counterparts.
- It has the lowest latency among all the LoRa class end devices for data communication between the server and the end device.
LoRa Class A, B, C | Key Differences
The table below summarizes the key differences between LoRa Class A, B, and C.
| Feature | LoRa Class A | LoRa Class B | LoRa Class C |
|---|---|---|---|
| Communication Type | Bi-directional with scheduled uplink and downlink slots | Bi-directional with additional scheduled receive windows | Bi-directional with continuous receive window |
| Latency | Highest latency due to limited downlink opportunities | Medium latency; downlink occurs at scheduled beacon slots | Lowest latency, always ready for downlink reception |
| Downlink Availability | Limited to two receive windows after each uplink | Downlink is available during scheduled beacon windows | Downlink is available anytime (almost continuous listening) |
| Power Consumption | Lowest, ideal for battery-powered devices | Medium, with periodic receiving during beacon times | Highest, due to constant listening mode |
| Payload type | Small payloads, long intervals | Small payloads, long intervals, Periodic beacon from gateway | Small payloads |
| Communication technique | Server communicates with end-device (downlink) during predetermined response windows | Server can initiate transmission at fixed intervals | End-device is constantly receiving |
| Synchronization | No synchronization with network beacons | Synchronizes with network beacons for scheduled communication | No synchronization required, always ready for downlink |
| Use Case | Suitable for low-power applications like sensors or metering | Suitable for applications needing predictable downlink response | Suitable for devices needing immediate response like actuators |
| Typical Applications | Environmental monitoring, periodic sensors | Smart meters, applications needing predictable downlink slots | Real-time applications, lighting control, actuators |
Note: Information provided on this page is derived from LoRaWAN Specification V1.0 released on Jan.2015 by LoRa™ Alliance. Read latest specifications published by LoRa Alliance (https://www.lora-alliance.org).
Conclusion
Class A devices prioritize minimal energy usage, making them ideal for battery-powered applications, while Class B and Class C offer more flexible scheduling options and lower latency. Class A is suited for low-power, periodic communication, while Class B and C provide more options for real-time communication and higher availability. A thorough understanding of these classes allows developers to design optimized IoT networks that maximize efficiency and meet application requirements effectively.
