This paper proposes a novel multiple access control (MAC) protocol, User-dependent Perfect-scheduling Multiple Access (UPMA) protocol, which supports joint transmission of voice and data packets. With the self-organizing algorithm, the exact number of mobile terminals (MT) in active state can be determined. Thus the transmission of MT can be perfectly scheduled by means of polling. Meanwhile, the unique frame structure of the UPMA protocol guarantees that the voice traffic is always transmitted prior to the data traffic. Furthermore, an effective collision resolution algorithm is proposed to guarantee rapid channel access for activated MT. Finally, performance of the UPMA protocol is evaluated by simulation and compared with the MPRMA protocol. Simulation results show that the UPMA protocol has better performance.