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New Anti-Collision Protocol Patent
eXI Wireless, a Canadian maker of RFID systems, has been granted a US patent for a way to enable a reader to scan hundreds of tags.
Jul 25, 2002—July 25, 2002 -- eXI Wireless Inc., a Richmond, BC, company that makes RFID asset management and security systems for the healthcare, energy and construction industries, has been granted a U.S. patent for the anti-collision features of its eLink wireless communication protocol.
When several RFID tags are in the field of a single reader, their signals interfere with one another, confusing the reader. Most anti-collision protocols require active, or battery-powered, tags to remain "awake" while they communicate with the reader until all their serial numbers are read.
To conserve battery life, eXI came up with a protocol that doesn't require all tags to remain awake. The reader sends out a signal that wakes up the tags and asks them to transmit the first bit of their serial number. The reader signals all the tags that don't send back a one to go back to sleep until later.
The reader keeps eliminating tags until it finds the one with the highest serial number. Then, it wakes up the other tags and goes through the process again. This happens so quickly that it appears as though the tags are being read simultaneously. The protocol works on up to 16 million tags.
Battery life is a key issue for eXI because it has developed what it claims is the world's smallest active RFID tag, which can't support a large battery. When the company was founded in the early 1980s, the system was originally used to track patients in hospitals and nursing homes, to make sure they didn't leave without authorization. The company adapted the system to protect newborn babies in hospitals.
"Health care is a complex environment," says eXI CEO Malik Talib. "You may have 20 wheel chairs in a room. A specific one is assigned to a specific patient, and if the patient gets the wrong chair, it screws up a lot of paperwork."
The protocol is also important for security and general asset tracking applications. If three people walk out of a building carrying laptops, a reader could communicate with tags in their badges and on their machines and know which person isn't authorized to leave with a computer. And because the systems reduces battery use, companies typically only have to replace batteries three or four years, depending on the application.
Talib took over as CEO of eXI four years ago and began expanding into other areas. eXI recently purchased a software company that built a system for tracking assets in the energy and construction fields using bar codes. eXI is now integrating its RFID hardware with the software systems to meet the needs of businesses in those fields.
The company, which is listed on the Canadian Venture Exchange under the symbol EXI, expects to receive patents in Canada, Europe and Asia.
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