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Multiuser downlink beamforming under quality of service (QoS) constraints has attracted considerable interest in recent years, because it is particularly appealing from a network operator's perspective (e.g., UMTS, 802.16e). When there are many co-channel users and/or the service constraints are stringent, the problem becomes in- feasible and some form of admission control is necessary. We advocate a cross-layer approach to joint multiuser transmit beamforming and admission control, aiming to maximize the number of users that can be served at their desired QoS. The problem is NP-hard; we propose and motivate a deflation approach based on second-order cone relaxation. For a moderate number of users, we benchmark the proposed algorithm against the optimal enumeration-based solution and a simpler approach, using both simulated and measured channel data. Our results indicate that the proposed algorithm yields consistently close to optimal performance at an affordable complexity cost.