Communication channel establishing method, communication system, and communication apparatus

A communication system comprising:

• a base station that transmits a beacon on a predetermined communication channel;
• and
• an electronic inventory tag including a communication unit that receives the beacon from the base station and establishes communication with the base station using the predetermined communication channel;
• wherein
• the base station detects whether a main power supply to supply power to the base station has been shut off, receives drive power from a backup power supply when the main power supply is shut off, and transmits a main power shutoff notification signal to the electronic inventory tag by wireless communication;
• the electronic inventory tag stores a current communication channel upon receiving the main power shutoff notification signal from the base station, the electronic inventory tag including a display unit to display information about products and being driven by a battery, and reestablishes wireless communication with the base station using the stored current communication channel upon recovery of the main power supply;
• the beacon includes an identification number of the electronic inventory tag with which the wireless communication is to be established;
• and
• the base station transmits the beacon periodically at a head of a frame, the frame including the beacon and a null beacon, the null beacon having a function different from the beacon.

An electronic inventory tag including a communications unit that receives a beacon from a base station and establishes communication using a communication channel according to the received beacon, the electronic inventory tag comprising:

• said communications unit that establishes wireless communication with the base station;
• and
• a control unit that stores a current communication channel of the electronic inventory tag upon receiving a main power supply shutoff notification signal indicating that a main power supply to supply power to the base station has been shut off from the base station via the communications unit, and searches subsequent beacons transmitted from the base station using the stored current communication channel,
• wherein the electronic inventory tag includes a display unit to display information about products and being driven by a battery,
• wherein the beacon includes an identification number of the electronic inventory tag with which the wireless communication is to be established, and
• wherein the base station transmits the beacon periodically at a head of a frame, the frame including the beacon and a null beacon, the null beacon having a function different from the beacon.