Some embodiments of the invention provide devices, systems and methods of clock synchronization. For example, a system in accordance with an embodiment of the invention includes a wireless access point to transmit a signal instructing a plurality of wireless communication stations to substantially simultaneously transmit wireless signals at a pre-defined time; and a wireless communication station including a synchronizer to synchronize, at a non allocated time slot, a clock of the wireless communication station to a clock of the wireless access point based on an estimated frequency offset of a data packet received from the wireless access point.