According to an embodiment of the invention, the PGM 412 may be coupled to the mobile communications device 411, receive the clock signal Ts, the information regarding the signal Tp of a start phase of a frame and the information regarding the total propagation delay Td from the mobile communications device 411, and adjust a reference clock according to the clock signal Ts, the information regarding the signal Tp and/or the information regarding the total propagation delay Td, such that a phase of the reference clock is synchronized with a phase utilized by the peer communications device. Note that here, the synchronization comprises synchronization in both frequency and phase.

For example, the clock signal Ts generated by the mobile communications device 411 may be already synchronized in frequency with the peer communications device. The PGM 412 generates the reference clock based on the clock signal Ts. The PGM 412 may comprise a phase alignment and compensation device 412-1 to compensate the signal Tp of a start phase of a frame for the timing delay according to the information regarding the total propagation delay Td, so as to generate the signal whose phase is almost aligned with that of the peer communications device. After performing the frequency and phase alignment and compensation on the start phase of the frame, for the back-end communications device, the spatial locations of the peer communications device and the data flow relay device may be regarded as almost the same.