Luke Pensworth
A new wireless sensor networking standard, DASH7, promises to become ubiquitous in phones, cars and homes, enabling RFID-like identification while communicating through walls. It’s similar to Zigbee, which uses the crowded 2.4 GHz band.
DASH7 defines the ISO standard for active radio frequency identification. It uses 433 MHz, a much lower frequency that travels further with less interference. It also uses less power and integrates RFID, providing a unique ID for every device. It may even be combined with Near Field Communications for remote payments via phone.
DASH7 combines existing radio-frequency identification with sensing technologies like Zigbee. It will enable “background location” for location-aware services. Longer range communications might even enable smart billboards, with customized personal messages. No retina scanning required. SoftGPS from Devicescape and Skyhook Wireless can supply location information without GPS.
The DASH7 Alliance, formed in 2009, has more than 20 members, including the U.S. Department of Defense which is using it to track goods and troops. Commercial vendors are also adopting Dash7 for energy monitoring devices in the home.
Unlike low power Bluetooth or Zigbee, DASH7 can link through walls. Two DASH7- devices can link together when they are within 300 feet. Unlike most active RFID technologies, DASH7 supports tag-to-tag communications for wireless “mesh” networking. OpenTag is an open source library for the DASH7 standard.
“DASH7 Mode 2 may be used for automotive applications like tire pressure monitoring, but smart buildings and mobile advertising also hold promise,” said Dr. Patrick King, Global Electronics Strategist for Michelin Corporation.
Benefits of DASH7 include:
- Multi-kilometer range and with penetration of walls, floors, and water.
- Extremely low power draw (measured in microwatts) and multi-year battery life
- A maximum bitrate of 200kbps
- Supports tag-to-tag or “multi-hop” communications, sensors, and public key encryption
- Extremely low latency for tracking moving objects
- Operation in the license-free and globally available 433 MHz spectrum
DASH7 features include:
- Operation at 433 MHz, globally available, unlicensed spectrum
- Based on ISO 18000-7 standard
- Multi-year battery life
- Range of up to 2 km (potentially farther)
- Penetration of concrete walls, water, and ability to “bend” around metal objects
- Data transfer at up to 27.77kpbs (potentially as high as 250kpbs)
- Sensor & security support
DASH7 is being developed for “smart” billboards and kiosks, as well as “smart” posters. License plates with embedded DASH7 RFID could be easily tracked. Ticketing, licensing, and passes can be deployed using flexible substrates and thin-film batteries that cost just a few bucks.
DASH7 is seen as a complement to Near Field Communications the technology that allows a cell phone to act as a charge card.
Contactless smart cards incorporate a chip that communicates with a card reader using (one-way) RFID to assure an identity. Near Field Communications uses short-range (two-way) wireless connections to maintain a transaction balance. Telecom operators enable contactless payments in phones using Near Field Communication for the link.
Near Field Communications has a range limited to a few inches and uses very low power transceivers at 13.56 MHz. Users of NFC phones in Asia and Europe simply bring their phones within a few inches of a turnstile or vending machine for near instantaneous transactions.
It automatically deducts the transaction from the balance held electronically in the phone. No PIN number required.
Both Near Field and DASH7 technologies can “co-exist” in the same silicon with only minor adjustments to the NFC silicon, says the DASH7 Alliance.
Money is becoming more mobile, explains NPR. But if your phone becomes your wallet, you don’t want to lose it.
Eliminating the need for an authenticating pin code could make NFC or DASH7 risky, say critics. Carrying more than one RFID/NFC authentication device has been proposed as a possible solution.
RFID-enabled cell phones are now available or under development for both the 13.56 and UHF (Gen-2) frequencies and market forecasts predict that up to 1 out of 2 phones in the future will be RFID-enabled, with the global emergence of RFID sensor networks anticipated.
GlobalTrak integrates DASH7 cargo tags to track cargo location via cellular networks. SAVI combines Dash7 with Iridium Modems for global tracking via satellite. The DoD’s In-Transit Visibility program is the world’s largest RFID network, tracking about 35,000 conveyances daily across more than 40 countries.
The Arecibo Observatory Amateur Radio Club used their 1000-foot dish for 432 MHz Earth-Moon-Earth radio bounce communications. Lacrosse satellites probably have antennas at least 100 feet in diameter.
The Air Force Pave Paws radar (AN/FPS-115), uses a 100 foot antenna array for missile and satellite tracking in the 420-450 MHz band.
Airplanes are more practical as an RFID interrogator, of course. Super RFID technology uses long-range radar responsive (RR) tags. The active 430 MHz tags employ RFID to transmit ID numbers instead of radar reflections. Radar using advanced beamforming is found in the Medium Extended Air Defense System, which uses both a UHF surveillance radar and X-band for Fire Control.
