| 摘要 |
PROBLEM TO BE SOLVED: To solve problems in the conventional art in which efficient power saving could not be attained because a synchronization signal had to be received each time for synchronization with a plurality of wireless nodes and because of a power control system being common to all the wireless nodes, and a correct synchronization signal could not be transmitted with respect to overlapping areas because of the same wireless channels being used for the synchronization signal and for data communication. SOLUTION: A wireless node includes a built-in time keeper having a correct clock, and the time keeper is initialized with a synchronization signal received at the start of operation to determine timing for change to a power saving mode and timing for return to a normal mode using the built-in clock. A wireless channel available for a synchronization signal and a wireless channel available for data transmission/reception are different channels. Since the synchronization signal does not need to be received each time, a power saving period can be prolonged and power saving control can be performed according to the wireless node. In addition, even if radio wave reaching areas overlap, a correct synchronization signal can be transmitted. COPYRIGHT: (C)2009,JPO&INPIT
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