Patent ID: 8416889

Claim:
A method of estimating transmission channel response and differences of synchronization offsets in a received stream of packets of OFDM data transmitted on a transmission channel, the stream of OFDM data being preceded by a header of symbols, the method comprising: performing, using a processor, a data-aided estimation of a channel response using the header when a packet is received, to thereby generate a corresponding estimated channel response value Ĥ p (k) for each sub-carrier (k) used in OFDM modulation; for a first received packet, storing the estimated channel response Ĥ l (k) as a refined channel response H l (k) for each of the sub-carriers (k), using the processor; for successive packets, using the processor to iteratively calculate a phase difference α p,p-1 (k) between the estimated channel response Ĥ p (k) for a current packet (p) and a refined channel response for a previous packet H p-1 (k) for each of the sub-carriers (k), estimate values of differences of synchronization offsets {tilde over (τ)} l (k) for each phase difference α p,p-1 (k) for each of the sub-carriers (k), choose a set of quantized values for each difference of synchronization offsets, choose, in the set of quantized values, a coarse estimation of the difference of synchronization offsets (τ′ p,p-1 ) for the current packet as a quantized value that maximizes a histogram of synchronization offsets {tilde over (τ)} l (k) versus quantized values, process values of a neighborhood of the coarse estimation (τ′ p,p-1 ) with an algorithm configured to calculate a refined difference of synchronization offsets for the current packet as a value that minimizes a sum of the Euclidean distances, for frequencies of the sub-carriers, between the estimated channel response Ĥ p (k) and the refined channel response H p-1 (k) rotated in a complex plane by a phase offset proportional to the refined difference of synchronization offsets, and calculate the refined channel response for the current packet H p (k) for each of the carriers (k) as a weighted average of a number p of received packets, of a rotated replica of the refined channel response H p-1 (k) multiplied by p−1 and the estimated channel response Ĥ p (k).