A system and method for synchronizing the phases and frequencies of devices in multi-user, wireless communications systems are provided. A primary beacon signal is transmitted by a destination node in a wireless communications network to a plurality of source nodes. Secondary beacon signals are also exchanged between the source nodes. Using the primary and secondary beacon signals, the nodes generate local phase and frequency estimates which are used to control local phases and frequencies of the source nodes. The source nodes then transmit common information to the destination at carrier frequencies based on the estimated local frequencies and phases, so that the phases and frequencies of the transmitted information are synchronized to facilitate coherent combining of the bandpass signals at the destination. Phase and frequency synchronization can be applied to wireless communications systems having any number of source nodes, and effects of Doppler shifts and moving platforms are accounted for. Acoustic and radio-frequency signaling can be utilized.