Consider the wireless communication system. There are mobile users. For each , user transmits a signal to the base station with power and an attenuation factor of (i.e., the actual signal power received at the base station from user is ). When the base station is receiving from user the total power received from all other users is considered interference (i.e., ). For the communication with user to be reliable, the signal-to-interference ratio must exceed a threshold , where the "signal" is the power received from user.