Wednesday, November 28, 2007

Research on Current Technique

We can identify the collision bit by bit if Manchester coding is used. This possibility is useful when there is not many tags in an interrogation area.

Weakness of Passive Tag:
Tag collisions is problematic as a tag has limited power and functionality. A passive tag can only transmit data by reflecting the reader transmitted electromagneticwaves, and hence, cannot detect nor communicate with the neighboring tags. The energy received by a tag is usually less than 100μW. Accordingly, CSMA-related methods are not practical anti-collision algorithms for the passive tags.

ISO 14443-3
Type A bit collision detection
Type B series of command sequence
ISO 15693
More detail about ISO, they are not just anti-collision protocols.

After review some anti-collision articles, I find out there are two main streams of anti-collision algorithm: ALOHA based and tree based. First one is probabilistic and the last one is deterministic.

After one weak research, I finished the first step in reviewing current papers about those proposed algorithms, and have better understanding the constrains existed in development process. I will concentrate on the most common scenario: passive tags with one reader sharing one channel, to consider the algorithm. Next step is brainstorming.

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