DASH7

DASH7 Alliance Protocol (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 () of the original standard document.
The current version of the DASH7 Alliance protocol is no longer 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).
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 Wi-Fi 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.
In January 2017, the DASH7 Alliance publicly released the v1.1 of the DASH7 Alliance Protocol. The version constitutes a major update of v1.0, in particular in the area of security and interoperability.
Technical summary.
DASH7 contrasts with existing wireless data technologies, after:
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.:
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.
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.
DASH7 provides a link budget of up to 140 dB with 27 dBm transmission power, which positions the technology as Medium Range, compared to Short Range (Bluetooth, Wi-Fi, ...) and Long Range (LoRaWAN, SigFox). Note that higher ranges are always obtained at the expense of per-bit power consumption and transmission duration. Low power long range technologies are generally not truly bi-directional as the regular scanning duty is pretty high. In this context, DASH7 is a very good compromise between range, power consumption, and bi-directionality and is very suitable for industrial applications with effective range of 100 m to 500 m.
In line-of-sight situations, 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.
Interoperability.
The DASH7 Alliance is currently working on a Certification program that tests functionally the DASH7 devices. The certification is composed of a set of test scenarios covering transactions in different stack configurations (channel, QoS, security). The physical wireless interface is not covered by the certification, and will have to comply to local radio regulations.
Alternative modulations.
The DASH7 Alliance policy does not allow to add proprietary or licensable modulation techniques in the official DASH7 Alliance Protocol. However, the layered structure of the protocol allows to easily integrate alternative modulations, such as LoRa, under the Network Layer (D7ANL).
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:
Developer support.
OSS-7: Dash7 open source stack.
The goal of the project is to provide a reference implementation of the DASH7 Alliance protocol. 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.
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.
Device integrators and Development Kits.
Many companies are members of the DASH7 Alliance to produce DASH7-compliant hardware products: