Estimation of CFO based on relative values of frequency bins corresponding to used subcarriers of received preamble symbols for OFDM systems
It is proposed a method for receiving and demodulating an orthogonal frequency division multiplexing signal received through a transmission channel (TC) by a receiver (RCV), comprising demultiplexing said signal to generate time symbols (y l (n)) and performing a time-to-frequency conversion of these time symbols to generate frequency bins (Y l (k)) corresponding to received symbols, the received symbols comprising preamble symbols. The method comprises: Determining an estimated carrier frequency offset on the basis of frequency bins corresponding to used subcarriers of the preamble symbols; Applying said estimated carrier frequency offset to the time symbols so as to correct the carrier frequency of these received symbols.
1. A method for receiving and demodulating an orthogonal frequency division multiplexing signal received through a transmission channel by a receiver, the method comprising:
Demultiplexing said signal to generate time symbols;
Performing a time-to-frequency conversion of said time symbols to generate frequency bins corresponding to received symbols, said received symbols comprising preamble symbols;
Determining an estimated carrier frequency offset by comparing to each other only the first and the last frequency bins corresponding to used subcarriers of said preamble symbols; and
Applying a corrective value based on said estimated carrier frequency offset, to said time symbols, so as to correct the carrier frequency of said received symbols.
2. A method according to claim 1 , wherein the corrective value is a frequency corrective signal determined from said estimated carrier frequency offset.
3. A method according to claim 2 , wherein said frequency corrective signal is a sine wave signal at a frequency determined by said estimated carrier frequency offset.
4. A method according to claim 3 , wherein said frequency corrective signal is mixed to said time symbols.
5. A method according to claim 1 , wherein the corrective value is a frequency corrective signal determined from said estimated carrier frequency offset, and the frequency corrective signal is applied to said time symbols by said time-to-frequency convertor.
6. A computer program product comprising a non-transitory computer readable medium, having thereon a computer program comprising program instructions, the computer program being loadable into a data-processing unit and when the computer program is run by the data-processing unit the program instructions cause the data-processing unit to be configured to:
demultiplex a received orthogonal frequency division multiplexing signal to generate time symbols;
perform a time-to-frequency conversion of said time symbols to generate frequency bins corresponding to received symbols, said received symbols comprising preamble symbols;
determine an estimated carrier frequency offset by comparing to each other only the first and the last frequency bins corresponding to used subcarriers of said preamble symbols; and
apply a corrective value based on said estimated carrier frequency offset, to said time symbols, so as to correct the carrier frequency of said received symbols.
7. A receiver for receiving and demodulating an orthogonal frequency division multiplexing signal received from a transmission channel, the receiver comprising:
a receiving unit configured for:
demultiplexing said signal to generate time symbols; and
performing a time-to-frequency conversion of said time symbols to generate frequency bins corresponding to received symbols, said received symbols comprising preamble symbols; and
a carrier frequency offset estimator configured for determining an estimated carrier frequency offset by comparing to each other only the first and the last frequency bins corresponding to used subcarriers of said preamble symbols; and
the receiving unit is further configured for applying a corrective value based on said estimated carrier frequency offset, to said time symbols, so as to correct the carrier frequency of said received symbols.
8. A receiver according to claim 7 , wherein the corrective value is a frequency corrective signal determined from said estimated carrier frequency offset and applied to said time symbols.
9. A receiver according to claim 8 , wherein said frequency corrective signal is a sine wave signal at a frequency FFC determined by said estimated carrier frequency offset so that FFC=*Δf Hz, where Δf is the inter subcarrier frequency.
10. A receiver according to claim 9 , wherein said frequency corrective signal is mixed to said time symbols before entering said time-to-frequency convertor.
11. A receiver according to claim 7 , wherein the corrective value is a frequency corrective signal determined from said estimated carrier frequency offset, and said frequency corrective signal is applied to said time symbols by said time-to-frequency convertor.