DASH7 is an open source wireless sensor networking standard for wireless sensor networking, which operates in the 433 MHz unlicensed ISM 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 public key encryption support, and data transfer of up to 200 kbit/s. DASH7 is the name of the technology promoted by the non-profit consortium called the DASH7 Alliance.
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DASH7 follows the ISO/IEC 18000-7 open standard for the license-free 433 MHz ISM band air interface for wireless communications. 433 MHz is available for use worldwide. The wireless networking technology was originally created for military use and has been re-purposed for mainly commercial applications in place of proprietary protocols like ZigBee or Z-Wave.
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 the DASH7 Alliance is doing for the ISO 18000-7 standard for wireless sensor networking.
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 effected by the communication data-rate, such that higher data-rates (e.g. 200-250Kbps) will yield a lower communication distance than 10Kbps. 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. 433MHz 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 contrasts with existing wireless data technologies like ZigBee:
| Technology | Global standard used | Frequencies used | Globally available frequency(ies)? | Rain Penetration | Location Granularity | Range | Average power draw | Average latency | Device cost | Multi-hop capabilities | Sensor and Security support | Interference from 802.11n | Maximum bit rate |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| DASH7 | ISO/IEC 18000-7 | 433.92 MHz | Yes | Higher | 1 meter | 1,000 m | Lower with remote wake-ups | 2 seconds worst case | $10+ | 2-Hops | Yes | No | 200 kbit/s |
| ZigBee[2] | IEEE 802.15.4 (partial) | 2.4 GHz, 915 MHz, 868 MHz | 2.4 GHz – yes; 915 MHz – no; 868 MHz – no | Lower | 10+ meters | 30–500 m | Higher with synchronous listening | varies from seconds to potentially minutes | $10+ | Yes | Yes | Yes | 250 kbit/s |
DASH7 utilizes the 433.92 MHz frequency, which is globally available and license-free. 433.92 MHz 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 for up to 10 years.
Note that 433.92 MHz is the same as 13.56 multiplied by the number 32, or 2^5th power, which effectively means DASH7 radios can utilize the same antennae used by 13.56 MHz radios including Near Field Communications, FeLiCa, MiFare, and other near-field RFID protocols.
Unlike most active RFID technologies, DASH7 supports tag-to-tag communications which, combined with the long range and signal propagation benefits of 433 MHz, makes it an easy substitute for most wireless "mesh" sensor networking technologies. DASH7 also supports sensors, encryption, IPv6, and other features.
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 BLAST:
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.
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.[3]
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:
Since NATO militaries continue to deploy DASH7 infrastructure, defense suppliers (see Classes of Supply) are expected to also deploy DASH7 infrastructure given NATO requirements for supply chain visibility beyond just physical boundaries of a given military and deep into the supply chains of an array of suppliers around the world. DASH7 is expected to be adopted similar to the way barcoding was rapidly adopted by commercial companies, many of whom are also defense suppliers, following the LOGMARS barcoding mandate from the U.S. Department of Defense in 1981.
DASH7 is being used extensively by the U. S. Department of Defense (DoD) and other militaries. In January 2009, DoD awarded a $429 million contract for DASH7 devices, making it one of the largest wireless sensor networking deployments in the world, especially when combined with DoD's $500 million + installed base of non-DASH7 infrastructure which DoD is upgrading to DASH7.[1]
Commenting on the U.S. Department of Defense's move to an RFID III multi-vendor contract earlier this year, Lt. Col. Pat Burden, the DoD's Product Manager Joint-Automatic Identification Technology, stated, "This is a significant milestone for DoD in that this migration will not only give DoD and other Federal agencies' customers best-value solutions at competitive prices, but it moves us to ISO 18000-7:2008 compliant products, thus broadening interoperability with DoD and our coalition partners."[8]
NATO military forces are required to interoperate with DoD's DASH7 network and are required to deploy interoperable infrastructure. All NATO militaries are deploying or in the process of deploying DASH7 infrastructure.[9]
DASH7 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. [10] proprietary) options elsewhere in the marketplace today.
OpenTag uses the Apache 2.0 open source license.
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).
OpenTag is available via Sourceforge at git://opentag.sourceforge.net/gitroot/opentag/OpenTag_M2
DASH7 developers receive support from the semiconductor industry including multiple options, with Texas Instruments, ST Microelectronics, Melexis, Semtech and Analog Devices all offering DASH7 hardware development kits or system-on-a-chip products.[11] Texas Instruments also joined the DASH7 Alliance in March 2009 and announced their CC430 system-on-a-chip product for DASH7 in December 2009.[12] Analog Devices also announced their ADuCRF101 single chip solution for DASH7 in November 2010.[13]
One semiconductor industry approach is the combination of DASH7 with MEMS sensing products:
"We strongly believe that the next big wave in sensors will be driven by the combination of the sensing function with wireless transmission – and ISO 18000-7 is the right solution for security and asset monitoring applications," said Benedetto Vigna, group vice president and general manager of the MEMS and Healthcare Product Division at STMicroelectronics in the company's announcement. "The Smart Web-Based Sensor HDK is a best-in-class development platform that will help the adoption of wireless sensors across the industry."[11]
ST Microelectronics announced the beta version of its DASH7 SmartSensor developers kit in May 2009 in collaboration with Arira Design.[14]
Another semiconductor industry approach focuses on automotive:
"There is a great potential for DASH7 technology in the automotive area," said Gilles Cerede, Product Line Manager for Wireless Automotive & Sensing at Melexis. "We see a perfect fit between DASH7 features and performance and the requirements of wireless safety applications. For example the ultra low power consumption matches the TPMS life time constraints, while the "multi-kilometer" communication range is perfectly suited for car-to-car and car-to-infrastructure applications. Last but not least, DASH7 is compatible from a frequency point of view with existing Remote Keyless Entry systems."
DASH7 is also seen as a complement to 13.56 MHz NFC (Near Field Communications), where both technologies can "co-exist" in the same silicon with only minor adjustments to the NFC silicon to accommodate DASH7.[15]
The DASH7 Alliance, through its partnership with the world renowned MET Laboratories, Inc. offers developers a complete set of test tools to allow for early testing of new DASH7 devices to ensure early in the development process that they will ultimately pass DASH7 Certified interoperability testing. Once products are completed, DASH7 Alliance members can access MET Laboratories test and certification facilities and, upon successfully completing certification testing, those members may use the "DASH7 Certified" logo on products that have successfully completed Alliance testing procedures conducted by MET.
Many companies are members of the DASH7 Alliance to produce DASH7-compliant hardware products, including:[16][17]
The original ISO 18000-7 standard was ratified in 2004 then modified in 2008. According to ISO:
ISO/IEC 18000-7:2009 defines the air interface for radio frequency identification (RFID) devices operating as an active RF tag in the 433 MHz band used in item management applications. It provides a common technical specification for RFID devices that can be used by ISO technical committees developing RFID application standards. ISO/IEC 18000-7:2009 is intended to allow for compatibility and to encourage inter-operability of products for the growing RFID market in the international marketplace. ISO/IEC 18000-7:2009 defines the forward and return link parameters for technical attributes including, but not limited to, operating frequency, operating channel accuracy, occupied channel bandwidth, maximum power, spurious emissions, modulation, duty cycle, data coding, bit rate, bit rate accuracy, bit transmission order, and, where appropriate, operating channels, frequency hop rate, hop sequence, spreading sequence, and chip rate. ISO/IEC 18000-7:2009 further defines the communications protocol used in the air interface.[18]
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