Demonstration on Practical Coherent Joint Transmission (CJT) with Phase Synchronization by Wireless Two-way Interferometry

This paper shows demonstration on coherent joint transmission (CJT) in down link (DL) with multiple distributed units (DUs), among which phase synchronization is established by Wireless two-way interferometry (Wi-Wi) that provides precise synchronization on carrier phase wirelessly and continuously in the manner of two-way phase transfer measured at intermediate frequency band by small-size and low-power consumption devices. It has been demonstrated through experiment conducted in a test field with 4 DUs that the proposed method brings comparable gain in CJT with ideal case; the loss relative to the gain by ideal CJT was 1.31 dB at 99% probability although the loss for the method without phase synchronization (only timing and frequency are synchronized) was more than 20 dB.