A receiver apparatus and a communication system wherein the frequency usage efficiency is raised to improve the communication throughput. The receiver apparatus comprises a receiving means that receives multicarrier signals in which a plurality of subcarriers are divided into a plurality of subcarrier blocks (frequency blocks) each including at least one subcarrier and in which signals to be transmitted to receiver apparatuses are arranged in those subcarrier blocks; an estimating means that estimates, for each of the subcarrier blocks, quality values indicative of the reception statuses of the signals arranged in the subcarrier blocks; and a notifying means that notifies a transmitter apparatus of information indicative of a high quality subcarrier block having a higher quality value than the other ones of the quality values, also notifies it of the quality value in the high quality subcarrier block, and further notifies it of the intervals of the subcarrier blocks each having a quality value the difference of which from the quality value in the high quality subcarrier block do not go beyond a predetermined threshold value.
