Patent ID: 7561510

Claim:
A communication system including a transmitter and a receiver, where the transmitter is applied to a second radio communication system using a second frequency band wider than a first frequency band used in a first radio communication system and the receiver is applied to the second wireless communication system using a second frequency band wider than a first frequency band used in a first wireless communication system, comprising: an occupation signal generation section for generating an occupation signal compatible with said first radio communication system and notifying said first radio communication system that said second radio communication system occupies a radio medium; a transmission section for performing communication in said second radio communication system after transmitting said occupation signal using every frequency in said second frequency band, wherein said transmission section transmits a start signal for notifying that the period during which communication is performed in said second wireless communication system starts; and a start judgment section for judging the start of the period during which said second wireless communication system occupies the radio medium based on said start signal received from the transmitter.