ML estimation of time and frequency offset in OFDM systems
IEEE Transactions on Signal Processing
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This paper presents a design and implementation on symbol synchronization and automatic gain control (AGC) for OFDM-based WLAN. Synchronization in OFDM-based receiver is critical for performance and needs a great deal of hardware resources. Based on the symmetries between real and imaginary values in short preamble of IEEE 802.11, applying the symmetries of a short preamble can reduce the hardware complexities of a matched filter to 30% of multipliers and 80% of adders necessary for a cross-correlator. This paper, contrary to the existing methods which use lookup table or CORDIC for phase estimation, also presents the phase estimation that the phase of complex signal can be found through binary search to reduce the amount of memory. To maintain the amplitude of incoming signal within the allowable operating range, the method of AGC in combination with receive signal strength indicator (RSSI) is also presented.