The disclosure generally relates to a shortened training field preamble structure for high-efficiency Wi-Fi environments. In one embodiment, the disclosure relates to a communication system having a transmitter transmitting a Master-Sync packet received by stationary and mobile receivers. The Master-Sync packet contains information for communicating in a HEW environment. Upon receipt each receiver decodes the Master-Sync packet to (i) estimate a frequency offset and/or an automatic gain control (AGC) setting; (ii) select a transmission frequency consistent with the frequency offset; and/or (iii) determine a new transmission power consistent with the AGC; (iv) tune to a new frequency offset and gain control setting to receive subsequent packets from the transmitter.