Patent ID: 7693129

Claim:
A system for frame and frequency synchronization in packet-based Orthogonal Frequency Division Multiplexing (OFDM), the system comprising: a. a frame synchronization module, the frame synchronization module enabling frame synchronization, the frame synchronization module comprising: i. a timing metric computing module, the timing metric computing module computing a timing metric, wherein the timing metric comprises a numerator, and a denominator, the numerator being lag-M auto-correlation of 2M-length sequence, M being the number of samples in each of the two identical halves of the preamble, the 2M-length sequence being obtained by multiplying a block of latest 2M samples of a received signal with 2M samples of the preamble, the denominator being an estimate of energy in the block of M samples of the received signal; and ii. a preamble boundary detecting module, the preamble boundary detecting module detecting the preamble boundary, the preamble boundary being detected based on a threshold, the threshold being determined a priori based on mean and variance of the timing metric at the preamble boundary and in neighborhood of the preamble boundary, the mean and the variance being estimated for an Additive White Gaussian Noise (AWGN) channel, the detection of the preamble boundary enabling frame synchronization; and b. a frequency-offset estimation module, the frequency-offset estimation module performing frequency-offset estimation after frame synchronization, the frequency-offset estimation enabling frequency synchronization, the frequency-offset estimation module comprising: i. a fractional-offset estimating module, the fractional-offset estimating module estimating a fractional part of the frequency-offset; and ii. an integer-offset estimating module, the integer-offset module estimating an integer part of the frequency-offset, the integer part of the frequency-offset being estimated by finding a Discrete Fourier Transform (DFT) of a M-length sequence, the M-length sequence being obtained by multiplying conjugate of M samples of the preamble in a transmitted signal with M samples of a corresponding block in a received signal, the corresponding block in the received signal being obtained after compensating with the fractional part of the frequency-offset, and by finding a DFT coefficient with largest magnitude, the DFT coefficient enabling the estimation of the integer part of the frequency-offset.