Dash7 Architecture and Protocol Stack for IoT

The Dash7 protocol is a robust and efficient wireless communication standard specifically designed for low-power IoT applications. Its unique architecture and versatile protocol stack enable seamless device communication in various sectors, including smart cities, industrial automation, and logistics. This guide explores the key components of the Dash7 architecture and delves into its protocol stack, highlighting its features and practical applications in the IoT ecosystem.

What is DASH7?

Dash7 is an open-source RFID standard used for Wireless Sensor Networking (WSN). It operates in the 433MHz frequency band and is promoted by the DASH7 Alliance. This technology offers a long battery life and a coverage range of about 2 Km in indoor environments.

Here are some key features of Dash7 wireless technology:

• DASH7 can communicate with NFC devices, even though NFC operates at 13.56 MHz and DASH7 operates at 433.92 MHz. NFC antennas can access higher-order harmonic frequencies of DASH7 radios.

DASH7 Architecture

The Dash7 network architecture consists of gateways, Dash7 devices, and internet connectivity. It can also communicate with NFC devices by modifying/altering frequencies. Dash7 gateways can query devices in their proximity without waiting for pre-defined time slots to listen to end-device beacons. This technology serves as a bridge between NFC and other IoT communication systems and can enable tag-to-tag communication without requiring a base station or tag reader.

DASH7 Protocol Stack

The Dash7 protocol stack is adaptable to the physical layers of Sigfox or LoRa.

Dash7 Communication Modes

RFID technologies such as NFC and Dash7 are widely used in WSN. Most smartphones integrate these technologies to provide building access, mobile payments, advanced location services, home automation, ticketing, and more. Dash7 is thus an integral part of the Internet of Things (IoT), acquiring sensor data and using it to manage social network applications.

There are four different device classes defined in the D7A (Dash7 Alliance Protocol):

• Blinker: Transmits only; does not use a receiver.
• EndPoint: Can transmit and receive data, and supports wake-up events.
• Subcontroller: A full-featured device that is not always active but uses wake-on-scan cycles similar to end points.
• Gateway: Connects the D7A network with other networks and is always online, listening unless it is transmitting.

All devices in a Dash7 network support one or more of these device classes.

DASH7 supports two communication models: pull and push. Dialogs between tags and interrogators are query-response-based (pull model), described by the D7A Query Protocol. Data transfer initiated from the tags to the gateway, on the other hand, is based on the push model, implemented as an automated message or beacon sent on specific time intervals (Beacon Transmit Series).

DASH7 Frame Types

DASH7 defines two types of frames: foreground frames and background frames.

• Foreground frames: Regular messages that contain data or data requests.

  Foreground frame = {length(1 byte), headers(3-38 bytes), payload(0 to 249 bytes), Footer(0 to 20 bytes), CRC16( 2 bytes) }
  

• Background frames: Very short broadcast messages used by the D7A Advertising Protocol for rapid ad-hoc group synchronization.

  Background frame = { subnet(1 byte), payload(3 bytes), CRC16(2 byte) }
  

Conclusion

Dash7 architecture and its protocol stack offer a powerful solution for low-power, long-range wireless communication in IoT applications. Its efficient design and support for multi-layer communication make it a preferred choice for industries ranging from logistics to smart infrastructure. As IoT continues to evolve, the Dash7 protocol remains a critical enabler, ensuring reliable and secure connectivity in diverse use cases. `