But the physics layer of some small hand-hold equipments can not provide carrier sense.

但在一些以小型手持设备为终端的自组网应用系统中物理层无法提供载波感知。

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The first is "the change of physics"on the layer of nature;

一是自然层面上的“物理之变”；

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The first is "the change of physics"on the layer of nature;

一是自然层面上的“物理之变”；

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