Timing drift compensation in wireless packet-based systems
First Claim
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1. A radio receiver system comprising:
- a radio receiver which receives plural modulated radio frequency carriers and produces therefrom a modulated base-band signal, the plural modulated radio frequency carriers having been transmitted by a radio transmitter operating in accordance with a transmitter sample clock;
a receiver sample clock which is used for sampling the modulated base-band signal;
a timing correction unit which performs in the frequency domain a timing drift compensation between the transmitter sample clock and the receiver sample clock;
a demodulation section which comprises the timing correction unit, and wherein the dcmodulation section further comprises;
a frequency offset estimation unit which outputs a frequency offset estimation;
frequency correction unit which receives the modulated base-band signal and outputs a frequency corrected modulated base-band signal;
a fast Fourier transform (FFT) unit which receives the frequency corrected modulated base-band signal and outputs a frequency domain modulated subcarrier signal;
a channel estimation unit which uses the frequency corrected modulated base-band signal to generate a frequency domain channel estimate which is applied to the timing correction unit;
wherein the timing correction unit generates a time corrected channel estimate;
a demodulator which uses the frequency domain modulated subcarrier signal and the time corrected channel estimate to generate a demodulated signal.
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Abstract
A radio receiver system (30) comprises a radio receiver (41), a receiver sample clock (60), which is used for sampling a modulated base-band signal; and a timing correction unit (100). The timing correction unit (100) performs, in the frequency domain, a timing drift compensation between a transmitter sample clock (66) and the receiver sample clock (60). In one example context of implementation, the plural modulated radio frequency carriers have been modulated using Orthogonal Frequency Division Multiplexing (OFDM).
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Citations
42 Claims
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1. A radio receiver system comprising:
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a radio receiver which receives plural modulated radio frequency carriers and produces therefrom a modulated base-band signal, the plural modulated radio frequency carriers having been transmitted by a radio transmitter operating in accordance with a transmitter sample clock; a receiver sample clock which is used for sampling the modulated base-band signal; a timing correction unit which performs in the frequency domain a timing drift compensation between the transmitter sample clock and the receiver sample clock; a demodulation section which comprises the timing correction unit, and wherein the dcmodulation section further comprises; a frequency offset estimation unit which outputs a frequency offset estimation; frequency correction unit which receives the modulated base-band signal and outputs a frequency corrected modulated base-band signal; a fast Fourier transform (FFT) unit which receives the frequency corrected modulated base-band signal and outputs a frequency domain modulated subcarrier signal; a channel estimation unit which uses the frequency corrected modulated base-band signal to generate a frequency domain channel estimate which is applied to the timing correction unit; wherein the timing correction unit generates a time corrected channel estimate; a demodulator which uses the frequency domain modulated subcarrier signal and the time corrected channel estimate to generate a demodulated signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A radio receiver system comprising:
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a radio receiver which receives plural modulated radio frequency carriers and produces therefrom a modulated base-band signal, the plural modulated radio frequency carriers having been transmitted by a radio transmitter operating in accordance with a transmitter sample clock; a demodulation section which comprises the timing correction unit, and wherein the demodulation section further comprises; a frequency offset estimation unit which outputs a frequency offset estimation; a frequency correction unit which receives the modulated base-band signal and outputs a frequency corrected modulated base-band signal; a fast Fourier transform (FFT) unit which receives the frequency corrected digital complex modulated base-band signal and outputs, for each subcarrier, a frequency domain modulated subcarrier signal which is applied to the demodulator; a channel estimation unit which uses the frequency corrected modulated base-band signal and generates a frequency domain channel estimate; wherein the timing correction unit receives the frequency offset estimation and the frequency domain modulated subcarrier signal to generate a time corrected frequency domain modulated subcarrier signal; a demodulator which uses the time corrected frequency domain modulated signal and the frequency domain channel estimate to generate a demodulated signal. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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21. A radio receiver system comprising:
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a radio receiver which receives plural modulated radio frequency carriers and produces therefrom a modulated base-band signal, the plural modulated radio frequency carriers having been transmitted by a radio transmitter operating in accordance with a transmitter sample clock; a receiver sample clock which is used for sampling the modulated base-band signal; a timing correction unit which performs in the frequency domain a timing drift compensation between the transmitter sample clock and the receiver sample clock; wherein the timing correction unit uses a frequency offset to determine a timing drift value, wherein the subcarrier signal comprises a stream of data symbols, further comprising; a frequency offset estimation unit which calculates; an estimated phase offset for each data symbol as a function of the data symbol; a predicted phase offset for each data symbol as a function of the estimated phase offset thereof and an estimated phase offset of a preceding one of the data symbols in the stream; a predicted sample phase offset for each data symbol as a function of a predicted phase offset of a corresponding one of the data symbol; and the frequency offset as a function of the predicted sample phase offset for each data signal sample. - View Dependent Claims (22)
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23. A method of operating radio receiver system comprising:
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receiving plural modulated radio frequency carriers and producing therefrom a modulated base-band signal, the plural modulated radio frequency carriers having been transmitted by a radio transmitter operating in accordance with a transmitter sample clock; sampling the modulated base-band signal in accordance with a receiver sample clock; performing in a frequency domain a timing drift compensation between the transmitter sample clock and the receiver sample clock; generating a frequency offset estimation; generating a frequency corrected modulated base-band signal; using a fast Fourier transform (FFT) unit to generate a frequency domain modulated subcarrier signal using the frequency corrected modulated base-band signal; using the frequency corrected modulated base-band signal to generate a frequency domain channel estimate; generating a time corrected channel estimate using the frequency domain channel estimate; using the frequency domain modulated subcarrier signal and the time corrected channel estimate to generate a demodulated signal. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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34. A method of operating radio receiver system comprising:
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receiving plural modulated radio frequency carriers and producing therefrom a modulated base-band signal, the plural modulated radio frequency carriers having been transmitted by a radio transmitter operating in accordance with a transmitter sample clock; sampling the modulated base-band signal in accordance with a receiver sample clock; generating a frequency offset estimation; generating a frequency corrected modulated base-band signal; using the frequency corrected digital modulated base-band signal and generating, for each subcarrier, a frequency domain modulated subcarrier signal; using the frequency corrected modulated base-band signal to generate a frequency domain channel estimate; performing in a frequency domain a timing drift comprising between the transmitter sample clock and the receiver sample clock by using the frequency offset estimation and the frequency domain modulated subcarrier signal to generate a time corrected frequency domain modulated subcarrier signal; using the time corrected frequency domain modulated signal and the frequency domain channel estimate to generate a demodulated signal. - View Dependent Claims (35, 36, 37, 38, 39, 40)
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41. A method of operating radio receiver system comprising:
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receiving plural modulated radio frequency carriers and producing therefrom a modulated base-band signal, the plural modulated radio frequency carriers having been transmitted by a radio transmitter operating in accordance with a transmitter sample clock; sampling the modulated base-band signal in accordance with a receiver sample clock; performing in a frequency domain a timing drift compensation between the transmitter sample clock and the receiver sample clock; using a frequency offset to determine a timing drift value, wherein the subcarrier signal comprises a stream of data symbols, further comprising calculating; an estimated phase offset for each data symbol as a function of the data symbol; a predicted phase offset for each data symbol as a function of the estimated phase offset thereof and an estimated phase offset of a preceding one of the data symbols in the stream; a predicted sample phase offset for each data symbol as a function of a predicted phase offset of a corresponding one of the data symbol; and
the frequency offset as a function of the predicted sample phase offset for each data signal sample. - View Dependent Claims (42)
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Specification