  Low latency and reliable information transfer are highly demanded in fifth
generation (5G) and beyond 5G wireless communications. A novel delay-bounded
wireless media access control (MAC) protocol called Carrier Sense Multiple
Access with Arbitration Point (CSMA/AP) was established to strictly ensure the
upper boundary of communication delay. CSMA/AP enables collision-free and
delay-bounded communications with a simple arbitration mechanism exploiting the
precise time synchronization achieved by Wireless Two-Way Interferometry
(Wi-Wi). Experimental demonstration and proving the feasibility in wireless
environments are among the most critical steps before any further discussion of
CSMA/AP and extension to various applications can take in place. In this work
described in this paper, we experimentally demonstrated the fundamental
principles of CSMA/AP by constructing a star-topology wireless network using
software-defined radio terminals combined with precise time synchronization
devices. We show that CSMA/AP was successfully operated, even with dynamic
changes of the spatial position of the terminal or the capability to
accommodate mobility, thanks to the real-time adaption to the dynamically
changing environment by Wi-Wi. We also experimentally confirmed that the
proposed CSMA/AP principle cannot be executed without Wi-Wi, which validates
the importance of precise time synchronization. This study paves the way toward
realizing delay-bounded wireless communications for future low-latency and
highly reliable critical applications.
