LoRa Tutorial: Frame Structure, Architecture, and Protocol Stack

This comprehensive LoRa tutorial delves into various aspects of LoRa technology, including its frame structure, network architecture, and protocol stack layers. It provides an in-depth understanding of how LoRa networks are constructed and how data flows between devices. By exploring each component, readers will gain valuable insights into the mechanics of LoRa communication and its applications in the IoT ecosystem.

LoRa technology is used as a wide-area network wireless technology. There are different frequency bands defined in the US (902 to 928 MHz), EU (863 to 870 MHz), China (779 to 787 MHz), and other regions to be used in LoRa wireless technology-based networks. It is a low-power, long-range, and low-data-rate technology developed with the initiative by Semtech.

LoRaWAN Architecture

The network architecture of LoRaWAN consists of gateways, network servers, and end devices. The network topology is a star of stars. End devices are also known as motes, and gateways are known as base stations or concentrators in LoRa network systems. End devices and Gateways are connected wirelessly using ISM bands specified with a single hop. Gateways and network servers are connected using IP backhaul connections.

Figure 1: LoRa network architecture

Customer information databases are housed in servers. Communication between end devices and gateways is carried at different channels and different data rates. LoRa supports adaptive data rates from 0.3 Kbps to 50 Kbps.

LoRa Frame Structure

Figure 2: LoRa Classes-A,B,C

The transmission from an end device to a gateway is referred to as “uplink,” and transmission from a gateway to an end device is referred to as “downlink.” There are different classes supported in the LoRaWAN network, viz. Class A, Class B, and Class C. As shown in the figure, the LoRa frame consists of an uplink part and a downlink part. In Class-A, the LoRa frame has one uplink slot followed by two downlink slots. The frame is as per the TDD topology.

LoRaWAN Protocol Stack

Figure 3: LoRa protocol stack

The figure depicts the LoRaWAN protocol stack consisting of the Application layer, MAC layer, PHY layer, and RF layer.

• Data from the application layer and MAC commands required to establish a connection between the End device and the gateway are carried as MAC payload.
• The MAC layer constructs the MAC frame using the MAC payload.
• The PHY layer uses the MAC frame as the PHY payload and constructs the PHY frame after inserting the Preamble, PHY header, PHY header CRC, and entire frame CRC.
• The RF layer modulates the PHY frame on the required ISM RF carrier as per regulatory requirements and transmits it onto the air.

Note: The information provided on this page is derived from the LoRaWAN Specification V1.0 released in Jan. 2015 by the LoRa™ Alliance. The LoRa alliance is responsible for changes to the specifications at any time without notice. RF Wireless World is not responsible for any issues regarding the same. Read latest specifications published by the LoRa Alliance (https://www.lora-alliance.org) for any changes required to be done for the products under development as per the LoRa standard.

Conclusion

This tutorial serves as a complete guide to understanding LoRa technology, covering everything from basic concepts to advanced topics. With knowledge of the frame structure, LoRaWAN architecture, and protocol stack layers, users can confidently design and implement LoRa-based networks. Whether for academic study or practical deployment, this guide provides a solid foundation for mastering LoRa technology and its applications in IoT solutions.