Frame detection method for 802.11b/g based WLAN systems

摘要

A method (and algorithm) for detection of 802.11a and 802.11b frames in an 802.11 transmission, calculates DCC (delayed copy correlation) and LCC (local copy correlation) magnitudes and compares their normalized values with threshold values. When a signal is detected, (i.e., AGC locks) the algorithm checks for a valid 802.11a frame, and it exploits the DCC properties of the received symbols. Because of the repetitions of short preambles in received symbols, the DCC is high when the short preamble symbols are present. Further, 802.11b detection may be based on Barker correlation properties simultaneously. A counter array is maintained for each position in a Barker window, and is incremented if the normalized LCC of the incoming sequence with the Barker code exceeds a threshold. An 802.11b packet is declared if the maximum value of the counter array exceeds a predetermined number in a specified number of Barker windows.