Apparatus and method for tracking symbol timing of OFDM modulation in a multi-path channel
First Claim
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1. A wireless signal receiver to demodulate an orthogonal frequency division multiplexing (OFDM) signal, said receiver comprising:
- power monitoring logic to determine an average power in a predetermined number of samples of null carriers which are frequencies in the OFDM signal where no carriers are transmitted; and
edge detection logic to detect rising edges of the average power of the null carriers, wherein each rising edge determines a location of a multipath component interfering with the OFDM signal, and the first rising edge indicates a first received multipath component which is used to control timing of a Fourier Transformation operation by Fast Fourier Transform (FFT) logic.
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Abstract
Methods and Systems for tracking symbol timing of an OFDM signal are disclosed. In one embodiment, a wireless receiver includes signal tracking and timing logic to facilitate the timing of a demodulation operation such that the demodulation operation occurs on the proper symbol boundary, particularly when the OFDM signal has multipath components and the second component has greater power than the first.
23 Citations
13 Claims
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1. A wireless signal receiver to demodulate an orthogonal frequency division multiplexing (OFDM) signal, said receiver comprising:
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power monitoring logic to determine an average power in a predetermined number of samples of null carriers which are frequencies in the OFDM signal where no carriers are transmitted; and edge detection logic to detect rising edges of the average power of the null carriers, wherein each rising edge determines a location of a multipath component interfering with the OFDM signal, and the first rising edge indicates a first received multipath component which is used to control timing of a Fourier Transformation operation by Fast Fourier Transform (FFT) logic. - View Dependent Claims (2, 3, 4)
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5. In a wireless signal receiver, a method of tracking symbol timing in a received orthogonal frequency division multiplexing (OFDM) signal having multipath components, comprising:
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monitoring, at the wireless signal receiver, a power of a null carrier portion which is a frequency of the received OFDM signal where no carrier is transmitted to detect a first increase in power caused by a multipath component interfering with the OFDM signal; and driving, at the wireless signal receiver, a Fast Fourier Transform (FFT) operation on the OFDM signal based on the first increase in power. - View Dependent Claims (6, 7, 8)
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9. A receiver, comprising:
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power monitoring logic configured to determine an average power in a predetermined number of samples of null carriers which are frequencies in an orthogonal frequency division multiplexing (OFDM) signal where no carriers are transmitted, wherein the power monitoring logic includes a sliding discrete Fourier Transform (DFT) DFT logic configured to perform a sliding DFT operation on samples on either side of the signal; and edge detection logic configured to detect rising edges of the average power of the null carriers to determine a location of a multipath component interfering with the OFDM signal, wherein the edge detection logic is further configured to provide symbol timing control signals to Fast Fourier Transform (FFT) logic to control timing of a Fourier Transformation operation performed by the FFT logic based on the detected rising edges. - View Dependent Claims (10, 11)
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12. A system, comprising:
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means for monitoring power within a null carrier portion which is a frequency of a received orthogonal frequency division multiplexing (OFDM) signal where no carrier is transmitted to detect a first increase in power in the null carrier portion, the first increase in power indicating a location of a multipath component interfering with the OFDM signal; and means for driving a Fast Fourier Transform (FFT) operation on the signal based on the detection of the first increase in power. - View Dependent Claims (13)
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Specification