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Understanding LoRaWAN Class A, B, C: Device Classes and Differences

lorawan iot device class power consumption latency

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.

LoRa Classes-A,B,C

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.