A method includes determining that a first receiver of a node of a mobile ad-hoc network (MANET) is in an electromagnetic contested environment for a first frequency. The method also includes scanning a frequency coverage range of a second receiver of the node for unused frequencies. The method additionally includes selecting a frequency from the unused frequencies, the selected frequency to be used for communication of messages from another node of the MANET to the node via the second receiver. The method further includes transmitting, to the other node, a message including information of the selected frequency via the transmitter.

Methods and apparatus to determine a level of inherent jitter for signals from a transmitter and a receiver, and modulate information onto a signal transmitted by the transmitter by using spot jitter (with bandwidth and center frequency modulation) and/or pulse width jitter in a region outside of a data region with inherent jitter to carry communication between systems.

A monitoring device (100) includes a communication connection unit (124). The communication connection unit (124) repeatedly executes connection to an unauthorized AP when the unauthorized AP exists in its surroundings, in order to fill simultaneous connection slots of the unauthorized AP, using each device identification information of one or more pieces of device identification information generated not to overlap each other. When connection to the unauthorized AP fails, the communication connection unit (124) connects to the unauthorized AP using device identification information of a damaged CL connected to the unauthorized AP, so as to disconnect communication connection between the unauthorized AP and the damaged CL, and connects to the unauthorized AP using other device identification information, in order to fill vacant simultaneous connection slots of the unauthorized AP that have become available due to disconnection of the communication connection.

There is disclosed an apparatus. The apparatus comprises means for performing: in response to detecting a jamming signal, obtaining a sample waveform of the jamming signal; and sending information of the jamming signal to another apparatus.