ROBUST INTEGER CARRIER FREQUENCY OFFSET ESTIMATOR
First Claim
1. A method of receiving an Orthogonal Frequency Division Multiplexing (OFDM) transmission, the method comprising:
- for each of a plurality of possible integer carrier frequency offset values, calculating a magnitude of a sum over selected sub-carriers of the OFDM transmission of products of a first quantity and a second quantity, wherein the first quantity is a difference between estimated channel responses of a first selected sub-carriers of the OFDM transmission, and the second quantity is a complex conjugate of a difference between estimated channel responses of a second selected sub-carriers of the OFDM transmission;
estimating as an integer carrier frequency offset value a possible integer carrier frequency offset value that produces the largest magnitude; and
using the estimated integer carrier frequency offset value to receive the OFDM transmission.
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Accused Products
Abstract
A robust integer carrier frequency offset estimation method for OFDM systems is disclosed. Compared with conventional methods which use either two consecutive OFDM symbols or only one training symbol, the method is insensitive to the timing offset as long as the channel spread is shorter than the OFDM cyclic prefix length. Most importantly, it does not require any information on the scrambling code used in systems such as STiMi. The method improves the accuracy of integer carrier frequency offset, especially in channels with long and strong echoes. It offers the receiver more freedom in setting the FFT window since it is insensitive to the timing offset.
35 Citations
24 Claims
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1. A method of receiving an Orthogonal Frequency Division Multiplexing (OFDM) transmission, the method comprising:
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for each of a plurality of possible integer carrier frequency offset values, calculating a magnitude of a sum over selected sub-carriers of the OFDM transmission of products of a first quantity and a second quantity, wherein the first quantity is a difference between estimated channel responses of a first selected sub-carriers of the OFDM transmission, and the second quantity is a complex conjugate of a difference between estimated channel responses of a second selected sub-carriers of the OFDM transmission; estimating as an integer carrier frequency offset value a possible integer carrier frequency offset value that produces the largest magnitude; and using the estimated integer carrier frequency offset value to receive the OFDM transmission. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. Apparatus for receiving an Orthogonal Frequency Division Multiplexing (OFDM) transmission, comprising:
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means for, for each of a plurality of possible integer carrier frequency offset values, calculating a magnitude of a sum over selected sub-carriers of the OFDM transmission of products of a first quantity and a second quantity, wherein the first quantity is a difference between estimated channel responses of a first selected sub-carriers of the OFDM transmission, and the second quantity is a complex conjugate of a difference between estimated channel responses of a second selected sub-carriers of the OFDM transmission; means for estimating as an integer carrier frequency offset value a possible integer carrier frequency offset value that produces the largest magnitude; and means for using the estimated integer carrier frequency offset value to receive the OFDM transmission. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. An apparatus for receiving an Orthogonal Frequency Division Multiplexing (OFDM) transmission, comprising:
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for each of a plurality of possible integer carrier frequency offset values, a calculator configured to calculate a magnitude of a sum over selected sub-carriers of the OFDM transmission of products of a first quantity and a second quantity, wherein the first quantity is a difference between estimated channel responses of a first selected sub-carriers of the OFDM transmission, and the second quantity is a complex conjugate of a difference between estimated channel responses of a second selected sub-carriers of the OFDM transmission; an estimator configured to estimate as an integer carrier frequency offset value a possible integer carrier frequency offset value that produces the largest magnitude; and an OFDM receiver configured to use estimated the integer carrier frequency offset value to receive the OFDM transmission. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24)
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Specification