A communication system includes a plurality of nodes performing communication via a common communication channel based on a communication protocol and including a first node or a second node. The first node transmits, to the communication channel, a wake-up frame as the communication frame for enabling the second node to transition from a sleep state to a normal state, determines whether or not the second node transitions to the normal state due to the wake-up frame, and generates an abnormal waveform pattern in the communication channel when determined that the second node does not transition to the normal state. The second node stores the identification information allocated to the second node, and enables the second node to transition from the sleep state to the normal state under on condition that the identification information included in the wake-up frame received from the communication channel is identical to the stored identification information.