DASH7

DASH7 Alliance Protocol (aka D7A) is an open source Wireless Sensor and Actuator Network protocol, which operates in the 433 MHz, 868 MHz and 915 MHz unlicensed ISM band/SRD band. DASH7 provides multi-year battery life, range of up to 2 km, low latency for connecting with moving things, a very small open source protocol stack, AES 128-bit shared key encryption support, and data transfer of up to 167 kbit/s. The DASH7 Alliance Protocol is the name of the technology promoted by the non-profit consortium called the DASH7 Alliance.

International standard

DASH7 Alliance Protocol originates from the ISO/IEC 18000-7 standard describing a 433 MHz ISM band air interface for active RFID. This standard was mainly used for military logistics.

The DASH7 Alliance re-purposed the original 18000-7 technology in 2011 and made it evolve toward a wireless sensor network technology for commercial applications. The DASH7 Alliance Protocol covers all Sub-GHz ISM bands making it available globally. The name of the new protocol was derived from the section seven denoted as -7 (/'dæʃ 'sevən/) of the original standard document.

The current version of the DASH7 Alliance protocol is no more compliant with the ISO/IEC 18000-7 standard.

History

In January 2009, the U.S. Department of Defense announced the largest RFID award in history, a $429 million contract for DASH7 devices, to four prime contractors: Savi Technology, Northrop Grumman Information Technology, Unisys and Systems & Processes Engineering Corp. (SPEC).^[1]

In March 2009, the DASH7 Alliance, a non-profit industry consortium to promote interoperability among DASH7-compliant devices, was announced, and as of July 2010 has more than fifty participants in twenty-three countries. Similar to what the WiFi Alliance does for IEEE 802.11, the DASH7 Alliance is doing for the ISO 18000-7 standard for wireless sensor networking.

In April 2011, the DASH7 Alliance announced adoption of DASH7 Mode 2, a next-generation version of the ISO 18000-7 standard that makes better use of modern silicon to achieve faster throughput, multi-hop, lower latency, better security, sensor support, and a built-in query protocol.

In March 2012, the DASH7 Alliance announced it was making the DASH7 Mode 2 specification available to non-members on an open source basis.

In July 2013, the DASH7 Alliance announced the DASH7 Alliance Protocol Draft 0.2.

In May 2015, the DASH7 Alliance publicly released the v1.0 of the DASH7 Alliance Protocol.

Technical summary

DASH7 contrasts with existing wireless data technologies, after:^[2]

BLAST networking technology

Networks based on DASH7 differ from typical wire-line and wireless networks utilizing a "session". DASH7 networks serves applications in which low power usage is essential, and data transmission is typically much slower and/or sporadic, like basic telemetry. Thus instead of replicating a wire-line "session", DASH7 was designed with the concept of B.L.A.S.T.:

• Bursty: Data transfer is abrupt and does not include content such as video, audio, or other isochronous forms of data.
• Light: For most applications, packet sizes are limited to 256 bytes. Transmission of multiple, consecutive packets may occur but is generally avoided if possible.
• Asynchronous: DASH7's main method of communication is by command-response, which by design requires no periodic network "hand-shaking" or synchronization between devices.
• Stealth: DASH7 devices does not need periodic beaconing to be able to respond in communication.
• Transitive: A DASH7 system of devices is inherently mobile or transitional. Unlike other wireless technologies DASH7 is upload-centric, not download-centric, thus devices do not need to be managed extensively by fixed infrastructure (i.e. base stations).

Sub 1-Ghz

D7A utilizes the 433, 868 and 916 MHz frequencies, which is globally available and license-free.

Sub 1-GHz is ideal for wireless sensor networking applications since it penetrates concrete and water, but also has the ability to transmit/receive over very long ranges without requiring a large power draw on a battery. The low input current of typical tag configurations allows for battery powering on coin cell or thin film batteries.

Tag-to-tag communications

Unlike most active RFID or LPWAN technologies, DASH7 supports tag-to-tag communications.

Localization

Localization techniques can be applied to DASH7 endpoints. An accuracy of 1m using DASH7 beacons at 433 MHz has been achieved in a lab experiment.^[3]

Integrated query protocol

DASH7 supports a built-in query protocol that minimizes "round trips" for most messaging applications that results in lower latency and higher network throughput.

Range

Note that "Range" is highly dependent on many factors including the transmitter's output power, such that higher power transmitters will be able to communicate at further distances at the immediate cost of increased power consumption. In addition, "Range" is also affected by the communication data-rate, such that higher data-rates (e.g. 200-250kbit/s) will yield a lower communication distance than 10kbit/s. Lower data-rates are more immune to channel-noise, thus effectively increasing signal-to-noise ratio and receiver sensitivity, as a result. The "Average Power Draw" also depends heavily on the communication duty cycle, i.e. how often the radio and micro-controller wake-up to send a packet. In addition to duty cycle, the average power draw is almost entirely dependent on the silicon-chip manufacturer's implementation, and has nothing to do with the choice of frequency (i.e. 433 MHz or 2.4 GHz). For example, CC2530 consumes 29mA at +1dBm transmit power, JN5148 consumes 15mA at +3dBm, and ATmega128RFA1 14.5mA at 3.5dBm. Sleep currents of the micro-controller with RAM retention is also equally important. How often you consume energy is application dependent.

DASH7 devices today advertise read ranges of 1 kilometer or more, however ranges of up to 10 km have been tested by Savi Technology and are easily achievable in the European Union where governmental regulations are less constrained than in the USA. Using frequency modulations used by LPWAN technologies, ranges of many kilometers are available.

Interoperability

DASH7 devices use a single global frequency, which simplifies deployment and maintenance decisions relative to specifications using multiple frequencies. A neutral, third party testing authority also conducts conformance and interoperability testing under the DASH7 Certified program.

Applications

Commercial applications

Similar to other networking technologies that began with defense sector (e.g. DARPA funding the Internet), DASH7 is similarly suited to a wide range of applications in development or being deployed including:

• Building Automation, Access Control, Smart Energy . DASH7's signal propagation characteristics allow it to penetrate walls, windows, doors, and other substances that serve as impediments to other technologies operating at 2.45 GHz, for example. For smart energy and building automation applications, DASH7 networks can be deployed with far less infrastructure than competing technologies and at far lower total cost of ownership.
• Location-Based Services DASH7 is being used today for developing new location-based services using a range of DASH7-enabled devices including smartcards, keyfobs, tickets, watches and other conventional products that can take advantage of the unique small footprint, low power, long range, and low cost of DASH7 relative to less practical and high-power wireless technologies like WiFi or Bluetooth. Using DASH7, users can "check in" to venues in ways not practical with current check-in technologies like GPS, that are power-intensive and fail indoors and in urban environments. Location-based services like Foursquare, Novitaz, or Facebook can exploit this capability in DASH7 and award loyalty points, allow users to view the Facebook or Twitter addresses of those walking past, and more.^[4]
• Mobile advertising DASH7 is being developed for "smart" billboards and kiosks, likewise "smart" posters that can be ready from many meters (or even kilometers) away, creating new opportunities for both tracking the effectiveness of advertising spend but also creating new e-commerce opportunities. DASH7's potential to automate check-ins and check-outs provides essential infrastructure to location-based advertising and promotions^[5]
• Automotive DASH7 is increasingly seen as the next-generation tire pressure monitoring system given its operation at the same frequency (433 MHz) as nearly all proprietary TPMS systems today. DASH7-based TPMS will provide end users with more accurate tire pressure readings, resulting in greater fuel economy, reduced tire wear and tear, and greater safety. DASH7 products are also being designed and used for other automotive applications like supply chain visibility.
• Logistics DASH7 is being used today for tracking the whereabouts of shipping containers, pallets, roll cages, trucks, rail cars, maritime vessels, and other supply chain assets, providing businesses with unprecedented visibility into their everyday operations. Also cold chain management (vaccines, fresh produce, cut flowers, etc.), whereby DASH7 is used for monitoring the in-transit temperature and other environmental factors that can impact the integrity of sensitive products.

Developer support

OSS-7: Dash7 Open Source Stack

The goal of the project is to provide a reference implementation of the DASH7 Alliance protocol.^[6] This implementation should focus on completeness, correctness and being easy to understand. Performance and code size are less important aspects. For clarity a clear separation between the ISO layers is maintained in the code. The project is available on github and is licensed under the Apache License, Version 2.0.

OpenTag

DASH7 Mode 2 developers benefit from the open source firmware library called OpenTag, which provides developers with a "C"-based environment in which to develop DASH7 applications quickly. So in addition to DASH7 (ISO 18000-7) being an open source, ISO standard, OpenTag is an open source stack that is quite unique relative to other wireless sensor networking (e.g. ZigBee) and active RFID (e.g. proprietary) options elsewhere in the marketplace today. Even though OpenTag is an Open Source project, people may not be able to use it free of charge. As of August 2015, there is no evidence to suggest OpenTag bears a royalty, although current versions of OpenTag OpenTag License do include a provision permitting RAND licensing:

4. RAND LICENSING

Any party who creates, redistributes and/or uses the Work or develops product(s) based on the Work (Using Party), must grant to any other party upon request, a nonexclusive, worldwide patent license on reasonable and non- discriminatory terms to any patent claims owned and/or licensed by the Using Party that are infringed by the Work or any standard based on the Work. Such Patent License may be royalty bearing.

OpenTag is a very purpose-built OS that offers a low level radio driver, PHY & MAC control system, event and session manager (OS-like), network protocols (M2NP, M2DP, M2AdvP) routing, raw data, group synchronization transport protocols (M2QP) query / data acquisition, data transfer filesystem read, write, create, delete, etc. C API library functions (Programming apps in C on the same device), Serial API(s) Client-Server (Communicating the apps via another device).

All versions of OpenTag are available as a git repository via Sourceforge & GitHub, and some versions are available as archives.

Semiconductor industry support

DASH7 developers receive support from the semiconductor industry including multiple options, with Texas Instruments, ST Microelectronics, Silicon Labs, Semtech and Analog Devices all offering DASH7 enabled hardware development kits or system-on-a-chip products.

ST Microelectronics announced the beta version of its DASH7 SmartSensor developers kit in May 2009 in collaboration with Arira Design.^[7]

Device integrators and Development Kits

Many companies are members of the DASH7 Alliance to produce DASH7-compliant hardware products:

• DASH7 Alliance members
• DASH7 Development Kits
• DASH7 Service Providers

References

External links

• DASH7 Alliance
• Low Power Wide Area Network Technology Comparison
• OSS-7 Open Source Stack
• OpenTag wiki