Design and Implementation of an OFDM WLAN Synchronizer

Abstract

With the advent of OFDM for WLAN communications, as exemplified by IEEE 802.11a, it has become imperative to have efficient and reliable synchronization algorithms for OFDM WLAN receivers. The main challenges with synchronization deal with the delay spread and frequency offset introduced by the wireless channel. In this work, rigorous research is done into OFDM WLAN synchronization algorithms, and a thorough synchronizer implementation is presented. This synchronizer performs packet detection, frequency offset estimation, and time offset estimation. Competing timing offset estimation algorithms are compared under a variety of channel conditions, with varying delay spreads, frequency offsets, and channel SNR. The metrics used to select between competing algorithms are statistical variance, and incremental hardware complexity. The timing offset estimation algorithms chosen are a dropoff detection algorithm for coarse timing offset estimation, and a quantized cross-correlator with a maximum detector for fine timing offset estimation.