In this paper, we propose a novel cross-layer approach of opportunistic scheduling to increase system throughput for IEEE 802.16 downlink transmission. Traditionally wireless users are scheduled according to the type of their subscribed service. The key idea of this paper is to combine hierarchical modulation with opportunistic scheduling, which not only yields a larger over-all system throughput, but also maintains the fairness determined by the type of traffic. As shown by the provided simulation results, the total information capacity for non real-time user is increased without penalizing much on the real-time user.