In this paper using a utility-based approach, downlink packet transmission in a CDMA/TDMA cellular network is formulated as an optimization problem. A utility function corresponds to each packet served by a base-station that is an increasing function of the packet experienced delay and the channel gain, and a decreasing function of the base-station load. Unlike previous works, in this paper, the optimization objective is to maximize the total network utility instead of the base-station utility. We show that this optimization results in joint base-station assignment and packet scheduling. Therefore, in addition to multi-user diversity, the proposed method also exploits multi-access-point diversity and soft capacity. A polynomial time heuristic algorithm is then proposed to solve the optimization problem. Simulation results indicate a significant performance improvement in terms of packet-drop-ratio and achieved throughput.