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