Iterative data-aided carrier frequency offset estimation for code division multiple access systems
View Patent ↗Iterative data-aided carrier CFO estimation for CDMA systems. Any communication receiver may be adapted to perform the iterative data-aided carrier CFO estimation. The iterative data-aided carrier CFO estimation is performed using a high accuracy method. The operation may be described as follows: a received signal is despread and buffered. Using the received preamble sequence, an initial estimate of the CFO is obtained. This estimate is used to correct the whole despread data. The corrected data using the initial CFO estimate is sliced. Each despread data symbol is divided by the corresponding sliced data decision. The obtained sequence is then averaged across different codes to obtain a less noisy sequence, which is then used to estimate the CFO again. The procedure can be repeated (iterated) to obtain a more accurate carrier frequency offset estimate; the number of times in which the procedure is repeated may be programmable or predetermined.
1. A communication device, comprising:
an input that is operable to receive a signal from a communication channel, the signal including a code division multiple access (CDMA) data packet having a preamble portion and a data portion; and
an iterative data-aided carrier frequency offset (CFO) module that is operable to:
generate a first CFO estimate of the CDMA data packet using the preamble portion;
employ the first CFO estimate to correct for CFO within the data portion of the CDMA packet; and
generate a second CFO estimate of the CDMA packet using the CFO corrected data portion.
2. The communication device of claim 1 , wherein:
the iterative data-aided CFO module is operable to generate the second CFO estimate of the CDMA packet using the CFO corrected data portion and the preamble.
3. The communication device or claim 1 , wherein:
the iterative data-aided CFO module is operable to employ the second CFO estimate to re-correct for CFO within the data portion of the CDMA packet; and
generate a third CFO estimate of the CDMA packet using the CFO re-corrected data portion.
4. The communication device of claim 1 , wherein:
the iterative data-aided CFO module is operable to perform a predetermined plurality of iterations when generating CFO estimates.
5. The communication device of claim 1 wherein:
the iterative data-aided CFO module is operable to perform a programmed plurality of iterations when generating CFO estimates.
6. The communication device of claim 1 , wherein;
the iterative data-aided CFO module is operable to:
modify the preamble portion using an expected preamble portion;
subgroup the modified preamble portion into a plurality of subgroups;
calculate a plurality of phase averages such that each phase average corresponds to one subgroup of the plurality of subgroups;
calculate a plurality of phase differentials such that each phase differential is a phase average difference between two adjacent subgroups of the subgroups; and
employ the plurality of phase differentials to generate at least one of the first CFO estimate and the second CFO estimate.
7. The communication device of claim 1 , wherein:
the communication device is operable to demodulate the signal using at least one of Binary Phase Shift Keying (BPSK), Quadrature Phase Shift Keying (QPSK), 16 Quadrature Amplitude Modulation (QAM), QAM, 32 QAM, 64 QAM, 128 QAM, 256 QAM, 516 QAM, and 1024 QAM.
8. The communication device of claim 1 , wherein:
the communication device is a multi-channel communication device;
a first channel of the multi-channel communication device is operable to receive the signal including the CDMA data packet; and
a second channel of the multi-channel communication device is operable to receive at least one additional signal that includes a time division multiple access (TDMA) data packet.
9. The communication device of claim 1 , wherein:
the communication device is a wireless communication device that is implemented within a wireless communication system.
10. The communication device of claim 1 , wherein:
the communication device is at least one of a multi-channel headend physical layer burst receiver, a base station receiver, a mobile receiver, a satellite earth station, a tower receiver, and a high definition television set top box receiver.
11. A communication device, comprising:
an input that is operable to receive a signal from a communication channel, the signal including a code division multiple access (CDMA) data packet having a preamble portion and a data portion; and
an iterative data-aided carrier frequency offset (CFO) module that is operable to:
generate a first CFO estimate of the CDMA data packet using the preamble portion;
employ the first CFO estimate to correct for CFO within the data portion of the CDMA packet; and
generate a second CFO estimate of the CDMA packet using the CFO corrected data portion and the preamble.
12. The communication device of claim 11 , wherein:
the iterative data-aided CFO module is operable to employ the second CFO estimate to re-correct for CFO within the data portion of the CDMA packet; and
generate a third CFO estimate of the CDMA packet using the CFO re-corrected data portion and the preamble.
13. The communication device of claim 11 , wherein:
the iterative data-aided CFO module is operable to perform a predetermined plurality of iterations or a programmed plurality of iterations when generating CFO estimates.
14. The communication device of claim 11 , wherein:
the communication device is a multi-channel communication device;
a first channel of the multi-channel communication device is operable to receive the signal including the CDMA data packet; and
a second channel of the multi-channel communication device is operable to receive at least one additional signal that includes a time division multiple access (TDMA) data packet.
15. The communication device of claim 11 , wherein:
the communication device is a wireless communication device that is implemented within a wireless communication system.
16. The communication device of claim. 11 , wherein:
the communication device is at least one of a multi-channel headend physical layer burst receiver, a base station receiver, a mobile receiver, a satellite earth station, a tower receiver, and a high definition television set top box receiver.
17. A method, comprising:
receiving a signal from a communication channel, wherein the signal includes a code division multiple access (CDMA) data packet having a preamble portion and a data portion;
generating a first CFO estimate of the CDMA data packet using the preamble portion;
employing the first CFO estimate to correct for CFO within the data portion of the CDMA packet; and
generating a second CFO estimate of the CDMA packet using the CFO corrected data portion.
18. The method of claim 17 , wherein:
the generating the second CFO estimate of the CDMA packet is performed using both the CFO corrected data portion and the preamble.
19. The method of claim 17 , further comprising:
employing the second CFO estimate to re-correct for CFO within the data portion of the CDMA packet; and
generating a third CFO estimate of the CDMA packet using the CFO re-corrected data portion and the preamble.
20. The method of claim 17 , wherein:
the method is performed within a communication device;
the communication device is a wireless communication device that is implemented within a wireless communication system.