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US 7,058,002 B1Granted
OFDM packet communication receiver
AssigneeNippon Telegraph and Telephone Corporation
InventorsTomoaki Kumagai, Masahiro Morikura, Masato Mizoguchi
Life of this patent
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Abstract
In an OFDM packet communication receiver, the deterioration of received signal quality is suppressed, even when carrier frequency error and/or clock frequency error exists between a transmitter and a receiver, and/or phase noise and/or thermal noise is superimposed to a received signal in a receiver.
Claims91
An OFDM packet communication receiver comprising:
- a receiving means (102) for receiving OFDM signals and carrying out a predetermined process to said OFDM signals,
- a synchronization means (103) for timing synchronization and carrier frequency synchronization for the received OFDM signals provided by said receiving means (102),
- a Fourier transform means (105) for carrying out Fourier transform of said received OFDM signals provided by said synchronization means to divide them into subcarrier signals for each OFDM symbol,
- a channel estimation means (106) for estimating channel condition of each subcarrier by using the subcarrier signals divided by said Fourier transform means,
- a coherent detection means (107) for carrying out coherent detection of the subcarrier signals divided by said Fourier transform means by using the channel estimation result provided by said channel estimation means,
- wherein a clock frequency error estimation means (100) for detecting phase rotation or accumulated phase rotation of a part or all of the coherently detected signals provided by the coherent detection means caused by clock frequency error between a transmitter and a receiver by detecting phase difference between the coherently detected signal (R1, R2) and a reference signal (S1 through S16), and generating phase rotation information (Δθ) of each subcarrier signal caused by said clock frequency error (fRCLK−fTCLK),
- a phase rotation compensation means (109) for compensating the phase rotation of the coherently detected signals provided by said coherent detection means caused by clock frequency error according to said phase rotation information generated by said clock frequency error estimation means, and
- a decision means (112) for decision processing for the phase compensated coherently detected signals provided by said phase rotation compensation means.
5 more elements
An OFDM packet communication receive system comprising:
- a receiving means for receiving OFDM signals and carrying out a predetermined process to said OFDM signals,
- a synchronization means for timing synchronization and carrier frequency synchronization for the received OFDM signals provided by said receiving means,
- a Fourier transform means for carrying out Fourier transform of said received OFDM signals provided by said synchronization means to divide them into subcarrier signals for each OFDM symbol,
- a channel estimation means for estimating channel condition of each subcarrier by using the subcarrier signals divided by said Fourier transform means,
- a coherent detection means for carrying out coherent detection of the subcarrier signals divided by said Fourier transform means by using the channel estimation result provided by said channel estimation means,
- a phase rotation compensation means for compensating phase rotation of the coherently detected signals provided by said coherent detection means caused by clock frequency error,
- a clock frequency error estimation means for detecting phase rotation of a part or all of the phase compensated coherently detected signals provided by the phase rotation compensation means caused by clock frequency error, generating phase rotation information of each subcarrier signal caused by said clock frequency error, and applying generated phase rotation:
- information to said phase rotation compensation means.
5 more elements
An OFDM packet communication receiver comprising:
- a receiving means for receiving OFDM signals and carrying out a predetermined process to said OFDM signals,
- a synchronization means for timing synchronization and carrier frequency synchronization for the received OFDM signals provided by said receiving means,
- a Fourier transform means for carrying out Fourier transform of said received OFDM signals provided by said synchronization menus to divide them into subcarrier signals for each OFDM symbol,
- a channel estimation means for estimating channel condition of each subcarrier by using the subcarrier signals divided by said Fourier transform means,
- a coherent detection means for carrying out coherent detection of the subcarrier signals divided by said Fourier transform means by using the channel estimation result provided by said channel estimation means,
- a residual carrier frequency error estimation means for estimating phase rotation of a part or all of an output of said coherent detection means caused by residual carrier frequency error,
- a phase rotation estimation means for estimating phase rotation of the coherently detected signal provided by said coherent detection means caused by clock frequency error according to carrier frequency error information supplied by said synchronization means and residual carrier frequency error information supplied by said residual carrier frequency error estimation means, and
- a phase rotation compensation means for compensating phase rotation of coherently detected signal provided by said coherent detection means caused by clock frequency error according to phase rotation information supplied by said phase rotation estimation means.
5 more elements
An OFDM packet communication receiver comprising:
- a receiving means for receiving OFDM signals and carrying out a predetermined process to said OFDM signals,
- a synchronization means for timing synchronization and carrier frequency synchronization for the received OFDM signals provided by said receiving means,
- a Fourier transform means for carrying out Fourier transform of said received OFDM signals provided by said synchronization means to divide them into subcarrier signals for each OFDM symbol,
- a channel estimation means for estimating channel condition of each subcarrier by using the subcarrier signals divided by said Fourier transform means,
- a coherent detection means for carrying out coherent detection of the subcarrier signals divided by said Fourier transform means by using the channel estimation result provided by said channel estimation means,
- a first phase rotation estimation means for estimating phase rotation of each subcarrier signal caused by clock frequency error according to carrier frequency error information supplied by said synchronization means,
- a first phase rotation compensation means for compensating phase rotation of coherently detected signals provided by said coherent detection means caused by clock frequency error according to phase rotation information provided by said first phase rotation estimation means,
- a residual carrier frequency error estimation means for estimating phase rotation of a part or all of phase compensated signals provided by said first phase rotation compensation means caused by residual carrier frequency error,
- a second phase rotation estimation means for estimating residual phase rotation caused by clock frequency error of the phase compensated signal provided by said first phase rotation compensation means according to the residual carrier frequency error information supplied by said residual carrier frequency error estimation means, and
- a second phase rotation compensation means for compensating residual phase rotation of the phase compensated signal provided by said first phase rotation compensation means caused by clock frequency error according to the residual phase rotation information supplied by said second phase rotation estimation means.
7 more elements
An OFDM packet communication receiver comprising:
- a receiving means for receiving OFDM signals and carrying out a predetermined process to said OFDM signals,
- a synchronization means for timing synchronization and carrier frequency synchronization for the received OFDM signals provided by said receiving means,
- a Fourier transform means for carrying out Fourier transform of said received OFDM signals provided by said synchronization means to divide them into subcarrier signals for each OFDM symbol,
- a channel estimation means for estimating channel condition of each subcarrier by using the subcarrier signals divided by said Fourier transform means,
- a coherent detection means for carrying out coherent detection of the subcarrier signals divided by said Fourier transform means by using the channel estimation result provided by said channel estimation means,
- a phase rotation information extraction means for extracting phase rotation information from a part or all of the output signals of said coherent detection means,
- a signal quality extraction means for extracting signal quality information of a part or all of the subcarrier signals divided by said Fourier transform circuit,
- a smoothing means for smoothing said signal quality information of each subcarrier provided by said signal quality extraction means along a time axis,
- a weighting means for weighting said phase rotation information provided by said phase rotation information extraction means according to smoothed signal quality information provided by said smoothing means,
- a common phase rotation detection means for detecting phase rotation of the coherently detected signals provided by said coherent detection means caused by residual carrier frequency error according to said weighted phase rotation information, and
- a phase rotation compensation means for compensating phase rotation of the coherently detected signals provided by said coherent detection means according to the estimated phase rotation information provided by said common phase rotation estimation detection means.
8 more elements
An OFDM packet communication receiver comprising:
- a receiving means for receiving OFDM signals and carrying out a predetermined process to said OFDM signals,
- a synchronization means for timing synchronization and carrier frequency synchronization for the received OFDM signals provided by said receiving means,
- a Fourier transform means for carrying out Fourier transform of said received OFDM signals provided by said synchronization means to divide them into subcarrier signals for each OFDM symbol,
- a channel estimation means for estimating channel condition of each subcarrier by using the subcarrier signals divided by said Fourier transform means,
- a coherent detection means for carrying out coherent detection of the subcarrier signals divided by said Fourier transform means by using the channel estimation result provided by said channel estimation means,
- specific symbol signal extraction means for extracting coherently detected signals in at least one specific OFDM symbol provided by said coherent detection means,
- a hard decision means for carrying out hard decision to the coherently detected signals extracted by said specific symbol signal extraction means,
- a first phase rotation detection means for detecting phase rotation of said extracted signals provided by said specific symbol signal extraction means according to the hard decision result provided by said hard decision means,
- a weight coefficient calculation means for calculating weight coefficient of each subcarrier signal corresponding to the signal quality according to the result of channel estimation provided by said channel estimation means,
- a weighting means for weighting phase rotation information detected by said first phase rotation detection means according to said weight coefficient of each subcarrier signal,
- a first common phase rotation detection means for detecting phase rotation common to each subcarrier signal caused by residual carrier frequency error according to said weighted phase rotation information provided by said weighting means,
- a pilot signal extraction means for extracting pilot signals from the coherently detected signals provided by said coherently detection means,
- a reference signal generating means for generating reference signals corresponding to the pilot signals extracted by said pilot signal extraction means,
- a second phase rotation detection means for detecting phase rotation of the pilot signals provided by said pilot signal extraction means,
- a second common phase rotation detection means for detecting phase rotation common to each subcarrier signal caused by residual carrier frequency error according to the phase rotation information provided by said second phase rotation detection means,
- a selection means for selecting one of the outputs of said first common phase rotation detection means and said second common phase rotation detection means according to the number of OFDM symbols provided by said coherent detection means,
- a phase rotation estimation means for estimating phase rotation caused by residual carrier frequency error of the coherently detected signals provided by said coherent detection means according to the selected phase rotation information provided by said selection means,
- a phase rotation compensation means for compensating phase rotation of the coherently detected signals provided by said coherent detection means according to the phase rotation information provided by said phase rotation estimation means.
15 more elements
Dependencies are inferred from the claim text.