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DASH7 Mode 2

DASH7 Mode 2 is a wireless air interface, and system stack, operating exclusively in the 433 MHz ISM band. It is designed and intended to be implementable on low-cost electronic hardware, typically consisting of a microcontroller (CPU) and digital RF transceiver.

  • It is designed and intended for bursty, wireless data applications requiring: average power budgets below 100µW, communication range exceeding 100m in any environment, latency between request and response below 1s, and no periodic transmissions (such as discovery beacons).
  • It is not designed or intended for applications requiring: single data payload transfers beyond 140 bytes, streaming data transfers (such as voice traffic), or burst transfers exceeding at most 10KB/s.

“DASH7” is a trade name for ISO/IEC 18000-7, a global standard for active RFID in the 433 MHz ISM band. Mode 2 is the most modern and capable variant of DASH7, that includes features typical of active RFID as well as WSN (wireless sensor networks), as well as some novel features.

Versioning and Formal Specification

The formal DASH7 specification can be downloaded for free right here.

See Also

Quickstart

The DASH7 Mode 2 specification is roughly 130 pages of 10 point Helvetica Neue on A4. There are dozens of tables and flow chart mixed in with the text, as well. To gain a complete understanding of DASH7 Mode 2 is not an easy task.

However, the truth is that you don't really need to understand everything in order to make great apps for DASH7. OpenTag is an open source project that implements all of the finer points of DASH7 Mode 2 and some of the broader points, too. Check out the OpenTag wiki on this site. Together with the OpenTag wiki, I have put together a quick DASH7 Mode 2 feature summary and DASH7 Mode 2 frame spec for hackers (the good kind of hackers, of course!).

Editorial Note: If you do want to download a PDF of the spec, stay tuned. I am working on getting the approvals and other sorts of mumbo-jumbo.

System Overview

Consider the DASH7 Mode 2 stack as a complete wireless solution covering OSI Layers 1 through 6, and to some extent Layer 7 as well (the application layer). Shown below is a table with a full stack overview for DASH7 Mode 2.

OSI Layer Mode 2 Component Description
Application (7) M2DEF Mode 2 Data Exchange Format for Applications
Secure Exchange Built-in Secure Exchange Protocol
Sensor Access Built-in Sensor Protocol (based on ISO 24151-7)
File Access Built-in File Access Protocol
Other Known Apps Compendium of known, non-built-in applications
Data Elements (6) Presentation Data presentation fundamental requirements
Mode 2 FS Lightweight filesystem with features resembling network ports, memory heaps, and normal filesystems: User privileges, Create/Delete/Read/Write, batch access
Crypto Table Volatile data structure for storage of host-host cryptographic key pairings
Session (5) Session Stack Unified session model with adaptive idling and priority to ad-hoc sessions over scheduled sessions (i.e. stack-based)
Transport (4) M2QP Mode 2 Query Protocol supports data-driven addressing, request/response, flow/congestion control, guaranteed delivery, and UDP adaptation
L4 Adaptation Methods for adaptation of UDP & TCP transport via M2QP
Network (3) M2NP Mode 2 Network Protocol used for routing and Network-Layer-Security (NLS)
Stream Frame A Network Layer primitive used as a concatenated frame in multi-frame packets
M2AdvP Mode 2 Advertising Protocol: a fixed length protocol (background protocol) for generating ad-hoc group synchronization.
M2ResP Mode 2 Reservation Protocol: basically identical to M2AdvP, except for advanced CSMA reservation. Not currently specified, just RFU.
NLS Network Layer Security: available for M2NP. NLS in Mode 2 encrypts the destination address but sends the source address in the clear.
Data Link (2) Frame Specification Two types: fixed-length “Background Frame” and variable-length “Foreground Frame”
Transfer Models Flood (Background Frame) and 1 Request → N Response (Foreground Frame)
Fundamental MAC CSMA-CA with dynamic channel guarding rules
Extended MACs RX wake-on, real-time synchronization, discovery beacons, guaranteed time-slots
Frame Addressing Broadcast, Unicast
Data Integrity CRC16 (Background Frame) and CRC5 + CRC16 (Foreground Frame), plus optional variable-length Reed-Solomon code
Data Link Security (DLLS) based on AES128-EAX with 32 bit integrity check
Physical (1) Channel QoS Clear Channel Assessment (CCA) with +/- 6 dB tolerance requirement
Encoding Types 1/1 (PN9-type), or optional 1/2 Interleaved Convolutional Code
Symbol Rate Multiple rates supported, up to 212kHz
Modulation FSK & MSK
Channeling Up to 15 channels
Spectrum 433.05 - 434.79 MHz (433 ISM Band)

Using IP with DASH7

(Placeholder)
DASH7 includes a mostly transparent UDP/IP Bridge at the M2QP Transport Layer. Addressing in DASH7 uses 64 bit UIDs which can be compliant with EUI-64, so the addressing conversion to/from IPv6 works the same way as it would in 6LoWPAN. For address conversion to/from IPv4, the entire IPv4 address can be stored inside the DASH7 UID.

Here is a list of other research papers, slideshows, etc, about DASH7. (Note: list is growing. There are actually a lot of DASH7 articles on the internet as well as my PC, but I need to upload them)

Introduction to DASH7 Technologies
An early paper by JP Norair from 2009 discussing ISO 18000-7 Mode 1, but many of the topics still apply to today's Mode 2. It describes some fundamentals of path-loss, RF modulation, antenna design, and low-power RF wakeup.

dash7_mode_2/main.txt · Last modified: 2015/04/27 23:43 by jpnorair