In this paper, I investigate a positioning system by a Fine Timing Measurement (FTM) network. In this system, each Access Point (AP) exchanges the FTM frames and Initiator broadcasts a frame which consists of its transmission and reception time. And a Rover just observes the frames from the APs and does not require to transmit any frame. In the proposed system, the simultaneous number of Rovers is not limited. I show some numerical results to evaluate the proposed system.