Patent ID: 7161896

Claim:
An apparatus for determining an estimate of the channel of each subcarrier in a wireless receiver for receiving OFDM data packets, the data packets transmitted as a set of subcarriers, the wireless receiver including: receive electronics to wirelessly receive and digitize a wirelessly transmitted OFDM data packet that includes a preamble having a known first symbol and a known second symbol, the receive electronics having an output outputting a set of received data samples, and a Fourier transformer having an input coupled to the output of the receive electronics, and an output forming a discrete Fourier transform (DFT) of the set of received data samples, the DFT of the received data samples forming a set of subcarriers corresponding to the set of received data samples, the apparatus including: a switch unit having an input coupled to the receive electronics accepting a function of a first set of received samples that corresponds to the first known symbol or of a second set of received samples that corresponds to the second known symbol, and having a first output and a second output, the switch unit connecting the input to the first output when the input is accepting the function of the first set of received samples and connecting the input to the second output when the input is accepting the function of the second set of received samples; a memory unit coupled to the first output of the switch unit, such that the memory unit is to store the function of the first set of received samples that corresponds to the first known symbol; an averaging unit having a first input coupled to the memory and a second input coupled to the second output of the switch unit, such that the averaging unit forms the average of the function of the first and second sets of received samples; a factoring unit having an input coupled to the output of the receiver's Fourier transformer, the factoring unit having an output producing a set of rough channel estimates, the factoring unit to factor out the set of subcarriers corresponding to the first known symbol or the second known symbol from the set of subcarriers determined by transforming the first or second set of received samples that corresponds to the first or second known symbol; and a smoothing filter having an input coupled to the output of the factoring unit to form smoothed channel estimates, such that the smoothed channel estimate for a particular subcarrier includes a contribution from channel estimates of the particular subcarrier's one or more immediate neighbors to take advantage of correlation that may exist between the particular subcarrier's channel and the channels of that subcarrier's one or more immediate neighbors.