Abstract: A device for estimating frequency offsets which is performed by periodically transmitting training signals from a wireless local area network system. The device includes a processor and computerized codes stored in a storage unit. The processor is configured to execute the computerized code to perform a method. The method includes receiving the plurality of training signals, selecting selected training signals by a predetermined interval from the received training signals, detecting and storing phases of the selected training signals, averaging phase differences of every pair of the detected phases of the selected training signals, calculating the frequency offsets according to an average of the phase differences for every pair of the detected phases of the selected training signals, and calculating a weighted average of the calculated frequency offsets using weighting values for each of the calculated frequency offsets.

Abstract: A communication system and an IoT system are provided. The IoT system is applicable to a wireless network system including an access point. The IoT system includes a WiFi module and a GPIO device. The WiFi module is configured to connect to the access point. The GPIO device is configured to provide a plurality of wake-up signals to the WiFi module through a GPIO pin. A predetermined time period between any two of wake-up signals is greater than an interval between two delivery traffic indication messages from the access point. The WiFi module includes a timer and a power management unit, the power management unit drains power to transfer the WiFi module from a sleep mode to a normal mode after the timer receives the wake-up signal.

Abstract: A method for estimating reception time of beacon signals includes receiving a beacon from a transmitting device, checking the real-time clock (RTC) of a receiving device, checking a timing synchronization function (TSF) of the received beacon, and estimating a reception time of a next beacon according to the RTC, TSF and a period of the beacon.