In this paper, we consider downlink transmission in a cellular wireless network, where a base station communicates with multiple mobile stations (MSs) over Nakagami-m fading channels. MSs are classified into two classes, and each class has its own minimum ergodic rate requirement. We propose an opportunistic scheduling and admission control scheme that aims at guaranteeing minimum ergodic rates for all MSs in the network. In order to maintain fairness among MSs in the same class and reduce the feedback load on the uplink of the network, our proposed scheme uses normalized SNR thresholds and exploits multiuser diversity with limited feedback. In our analysis, we give a formula by which we can easily check whether an incoming MS, who requests to join a class in the network, can be accepted or not. For accepted MSs in the network, we obtain the values of thresholds with which all MSs in the network can be guaranteed respective minimum ergodic rate requirements. Through numerical studies and simulations, we confirm the validity of our scheme and analysis, and show the usefulness of our scheme.