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Introduction Overview of RFID Technology Physics of RFID RFID Middleware RFID Application Help Exit

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Anticollision

Simultaneous transmissions in RFID systems lead to collisions. Communication between a single reader and a single tag can go without any collision. But when a single reader is communicating with morę than one tag or two or morę readers are operating in a closer network, probability of colliding of data arises. To solve this problem, we use some protocols like ALOHA, binary tree, query tree etc.

Conventional Slotted ALOHA Algorithms

Downlink

Request

*(1)¹

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10110011

10100011

10111010

Reader

11110101

BFSA has the fixed frame size N (N slots in one frame) and N = 3 in above fig.

Conventional Slotted ALOHA Algorithms

Number of RFID tags —^ Collision ratę —^ Tag recognition ratę

1

In worst cases, no tag may be identified though the repeated reading cycle if a lot of tags exist and all the slots are filled with tag collision.