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We propose a PHY-MAC cross-layer based dynamic-resource allocation (DRA) scheme with diverse QoS guarantees for heterogeneous mobile users over MIMO-OFDM wireless network downlinks. Our scheme differentiates real-time users (e.g., audio/video) from non-real-time users (e.g., data). At the PHY layer, the DRA adaptively allocates transmit antennas and modulation levels for real- and non-real-time users to increase the spectral efficiency while guaranteeing the distinct BER-QoS requirements. Combining with the proposed PHY-layer infrastructure, the DRA at the MAC layer treats real- and non-real-time users differently: (1) it dynamically assigns time-slots for real-time users in a TDM-mode to guarantee the bounded delays; (2) it adaptively allocates subcarriers for non-real-time users in an FDM-mode to maximize the system throughput while retaining fairness among users. We analytically derive the admission-control and time-slot allocation conditions to guarantee the statistical delay-bound for real-time users using the effective bandwidth theory. Also, extensive simulations are conducted to evaluate the performance of our proposed scheme.