Patent ID: 7899000

Claim:
A communication method of a communication system having a base station for performing a call and a terminal for returning a response to the call from the base station, the communication method comprising the steps of: transmitting the call by the base station, the call including response probability; setting a contended access period including a plurality of communication slots by the terminal after the call is transmitted; generating a random number by the terminal; deciding whether to respond to the base station by the terminal based on a comparison between the random number and the response probability when the call from the base station is received; randomly selecting one of the plural communication slots by the terminal; and responding to the base station at a timing corresponding to one of the randomly selected communication slots by the terminal when the call from the base station is received; shifting the terminal to a sleep status in a case where the response probability is less than the generated random number; wherein only minimum necessary circuits in the terminal are in operation, and operation of unnecessary circuits in the terminal are stopped when the terminal is in the sleep status.