With the fast progress of Collaborative multimedia application (CMA) running on overlay network, Push to talk over cellular (PoC) attracts signifi- cant interest in the field of mobile cellular communications. PoC is an on-demand, resource efficient, half-duplex multimedia service. Due to the half-duplex nature, only one user is allowed to speak at a time, and the others listen. If listeners want to speak, they have to contend for the right to speak and wait for the permission if request waiting is supported. Open mobile alliance (OMA) proposed a centralized controlling based floor control mechanism for speak right coordination in PoC, which is called Talk burst control protocol (TBCP). But it has many limitations in scalability, reliability and robustness as all centralized approaches have. In addition, none of available distributed approaches well meets mobile users' requirements in PoC, especially for the request waiting function. In this paper we put forward a novel distributed floor control mechanism with request waiting for PoC, which is called Distributed floor control mechanism (DFCM). From the performance evaluation of DFCM and TBCP, we find that DFCM outperforms TBCP especially when performance of the central node, Controlling server (CS), drops down due to heavy load. Finally, this paper is summarized and future work is forecasted.