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An advanced CSMA/CA (carrier sense multiple access with collision avoidance) system incorporating total precedence transmission of all CA and MAC frames (known as a full-flying synchronous CSMA/v-MCA system in Japan, where v- MCA means a variable multiple CA) was developed to minimize the time wasted for upstream channels. In this system, the CA procedures and the controls of the MAC frame transmission run independently of each other by adopting out-of-band signaling (OBS) in order to achieve flexible access control. However, in highly offered traffic, MAC frames, that have completed the CA procedure, queue to be transmitted, causing latency to increase rapidly. To solve this problem, the CA and MAC channels are properly distributed, and flow control is added to the CA procedure. In this study, the performance of this system was evaluated and confirmed using a theoretical calculation and a computer simulation. Maximum throughput of approximately 0.9 was observed regardless of network length (up to tens of kilometers) and physical transmission speed, maintaining the low latency that is characteristic of contention systems.