Abstract: A communication method of wireless internet of things under asynchronous frequency hopping networking includes steps of: S10, network-wide channel and time slot planning; S20, network negotiation; S30, network access of first-level child nodes; S40, network access of second-level child nodes; and S50, network maintenance and service message transmission. The communication method is simple, and easy to operate, which releases network configuration message through signaling channels, and can realize efficient networking, wherein each child node carries out frequency hopping communication in accordance with different frequency hopping sequences. The channel utilization rate is effectively improved through asynchronous frequency hopping of all the nodes in the whole network.

Abstract: A method for extracting a characteristic signal from a power frequency signal includes steps of: S1, detecting a voltage half-wave zero-crossing area in a single voltage cycle in the power frequency signal by a signal; superimposing a voltage modulation signal on the voltage half-wave zero-crossing area, and superimposing an instantaneous pulse on a current cycle in the power frequency signal corresponding to the voltage half-wave zero-crossing area; generating the characteristic signal with current cycles and voltage cycles; S2, demodulating whether there is the voltage modulation signal in the power frequency signal, if so, executing step S3; and S3, demodulating the characteristic signal to obtain the current modulation signal and the voltage modulation signal respectively; and determining whether data corresponding to the current modulation signal and date corresponding to the voltage modulation signal are predetermined data, wherein if so, the characteristic signal exists.