Preamble detection with unknown channel
First Claim
1. A system, comprising:
- a differential demodulation module that differentially demodulates modulated signals to generate differentially demodulated signals,wherein the modulated signals include subcarriers,wherein every Pth one of the sub-carriers is modulated with a preamble bit, where P is an integer greater than or equal to 1, andwherein the differential demodulation module generates the differentially demodulated signals by multiplying a Qth one of the modulated signals by a complex conjugate of a (Q+P)th one of the modulated signals, where Q is an integer greater than or equal to 1;
a correlation module that generates correlation values based on a correlation of the differentially demodulated signals with derived preamble sequences, wherein each one of the correlation values has a real part and an imaginary part; and
a control module that selects one of the correlation values having a largest real part and that detects a preamble sequence in the modulated signals upon determining that the largest real part is greater than or equal to a predetermined threshold.
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Accused Products
Abstract
A system includes a differential demodulation module that differentially demodulates modulated signals to generate differentially demodulated signals. A correlation module correlates the differentially demodulated signals with derived preamble sequences and generates correlation values. The derived preamble sequences are derived from preamble sequences. One of the derived preamble sequences is generated by combining bits of one of the preamble sequences using an exclusive OR function. Each bit of one of the derived preamble sequences has a first state when a corresponding bit and a bit adjacent to the corresponding bit in a corresponding one of the preamble sequences have opposite states. The each bit has a second state when the corresponding bit and the bit adjacent to the corresponding bit have the same state.
27 Citations
35 Claims
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1. A system, comprising:
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a differential demodulation module that differentially demodulates modulated signals to generate differentially demodulated signals, wherein the modulated signals include subcarriers, wherein every Pth one of the sub-carriers is modulated with a preamble bit, where P is an integer greater than or equal to 1, and wherein the differential demodulation module generates the differentially demodulated signals by multiplying a Qth one of the modulated signals by a complex conjugate of a (Q+P)th one of the modulated signals, where Q is an integer greater than or equal to 1; a correlation module that generates correlation values based on a correlation of the differentially demodulated signals with derived preamble sequences, wherein each one of the correlation values has a real part and an imaginary part; and a control module that selects one of the correlation values having a largest real part and that detects a preamble sequence in the modulated signals upon determining that the largest real part is greater than or equal to a predetermined threshold. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A system comprising:
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a differential demodulation module that differentially demodulates modulated signals to generate differentially demodulated signals; and a correlation module that correlates the differentially demodulated signals with derived preamble sequences and that generates correlation values, wherein the derived preamble sequences are derived from preamble sequences, wherein one of the derived preamble sequences is generated by combining bits of one of the preamble sequences using an exclusive OR function, and wherein (i) each bit of one of the derived preamble sequences has a first state when a corresponding bit and a bit adjacent to the corresponding bit in a corresponding one of the preamble sequences have opposite states, and (ii) the each bit has a second state when the corresponding bit and the bit adjacent to the corresponding bit have the same state.
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18. A system comprising:
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a differential demodulation module that differentially demodulates modulated signals to generate differentially demodulated signals; a correlation module that correlates the differentially demodulated signals with derived preamble sequences and that generates correlation values, wherein the derived preamble sequences are derived from preamble sequences, wherein one of the derived preamble sequences is generated by combining bits of one of the preamble sequences using an exclusive OR function, wherein the modulated signals include sub-carriers that are modulated using orthogonal frequency domain multiplexing (OFDM), wherein every Pth one of the sub-carriers is modulated with a preamble bit, where P is an integer greater than or equal to 1, and wherein the every Pth one of the sub-carriers has substantially a same differential channel phase; and a control module that selects a largest correlation value from the correlation values and that detects a preamble sequence in the modulated signals upon determining that a magnitude of the largest correlation value is greater than or equal to a predetermined threshold, wherein the control module calculates a symbol timing offset by multiplying a phase angle of the largest correlation value by (N/2π
P), where N is a number of sub-carriers in an N fast Fourier transform (FFT) mode, and where N is an integer greater than 1. - View Dependent Claims (19)
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20. A method, comprising:
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differentially demodulating modulated signals to generate differentially demodulated signals, wherein the modulated signals include subcarriers, wherein every Pth one of the sub-carriers is modulated with a preamble bit, where P is an integer greater than or equal to 1, and wherein the differentially demodulated signals are generated by multiplying a Qth one of the modulated signals by a complex conjugate of a (Q+P)th one of the modulated signals, where Q is an integer greater than or equal to 1; correlating the differentially demodulated signals with derived preamble sequences; generating correlation values based on the correlating; determining a real part and an imaginary part of each one of the correlation values; selecting one of the correlation values having a largest real part; and detecting a preamble sequence in the modulated signals upon determining that the largest real part is greater than or equal to a predetermined threshold. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32)
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33. A method comprising:
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differentially demodulating modulated signals; generating differentially demodulated signals from the modulated signals; correlating the differentially demodulated signals with derived preamble sequences, wherein the derived preamble sequences are derived from preamble sequences, and wherein one of the derived preamble sequences is generated by combining bits of one of the preamble sequences using an exclusive OR function; and generating correlation values based on the correlating, wherein (i) each bit of one of the derived preamble sequences has a first state when a corresponding bit and a bit adjacent to the corresponding bit in a corresponding one of the preamble sequences have opposite states, and (ii) the each bit has a second state when the corresponding bit and the bit adjacent to the corresponding bit have the same state.
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34. A method comprising:
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differentially demodulating modulated signals; generating differentially demodulated signals from the modulated signals; correlating the differentially demodulated signals with derived preamble sequences, wherein the derived preamble sequences are derived from preamble sequences, and wherein one of the derived preamble sequences is generated by combining bits of one of the preamble sequences using an exclusive OR function; generating correlation values based on the correlating; differentially demodulating sub-carriers that are included in the modulated signals and that are modulated using orthogonal frequency domain multiplexing (OFDM), wherein every Pth one of the sub-carriers is modulated with a preamble bit, where P is an integer greater than or equal to 1; differentially demodulating the sub-carriers, wherein the every Pth one of the sub-carriers has substantially a same differential channel phase; selecting a largest correlation value from the correlation values and detecting a preamble sequence in the modulated signals upon determining that a magnitude of the largest correlation value is greater than or equal to a predetermined threshold; and calculating a symbol timing offset by multiplying a phase angle of the largest correlation value by (N/2π
P), where N is a number of sub-carriers in an N fast Fourier transform (FFT) mode, and where N is an integer greater than 1. - View Dependent Claims (35)
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Specification