Patent ID: 8217794

Claim:
An active radio frequency identification system for port logistics using multi-hop communication, the radio frequency identification system comprising: a reader; and a plurality of tags, wherein the tags include a first tag including: a command receiving unit receiving a command selected from the group consisting of a peer-to-peer command and a broadcast command of the reader, wherein the command was issued from one selected from the group consisting of the reader and other tags; a response message transmitting unit for transmitting a response message to one selected from the group consisting of the reader and the other tags which transmitted the command to the command receiving unit; a command transmitting unit retransmitting the command received by the command receiving unit to the other tags; a response message receiving unit receiving a response message transmitted from the other tags which received the command retransmitted by the command transmitting unit; a command reconstructing unit reconstructing a broadcast command by adding an ID of the first tag which is reconstructing the command and a level value indicating the number of hops the command completed from the reader to the first tag, when the command received by the command receiving unit is the broadcast command, and providing the reconstructed broadcast command to the command transmitting unit; a response message reconstructing unit reconstructing a response message by adding information, the level value, and an ID of the tag which transmits the command to the command receiving unit to the response message, when the broadcast command received from the command receiving unit is the command transmitted from the other tags, and providing the reconstructed response message to the response message transmitting unit, wherein said information added to the response message is a relay command, wherein the relay command is added to a mode field, which is the highest four bits in the response message so as to distinguish a command retransmitted from the other tag from a received command, the level value added in the command reconstructing unit is stored in two bits after the mode field, and the ID of the tag, which transmits the command to the command receiving unit, is added to last four bytes of a data field of the response message; and a tree-based child table recording a lower tag, which transmits the response message received from the response message receiving unit, as a child tag and a higher tag, which transmits the broadcast command received from the command receiving unit, as a parent tag, and storing a tree-based network topology.