Method and apparatus for efficient preamble detection in digital data receivers
First Claim
1. A method for preamble detection in digital data receivers, comprising the steps of:
- providing a power estimation means for producing a value of modulation power where;
powerk=abs(real(Rk)·
real(Rk-N))+abs(imag(Rk)·
imag(Rk-N)).
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Accused Products
Abstract
Traditional techniques for data reception in burst-mode receivers are of significant complexity. To aid detection, most burst-mode systems transmit a preamble, or predetermined data pattern, at the start of each new block of data. Using current methods, the detection of a new preamble, indicating the arrival of a new burst of data, is particularly complex. A method and apparatus is disclosed that significantly reduces this detection complexity, while maintaining superior signaling performance. This simplification can lead to higher data throughput within processing-limited receivers, and/or a greater degree of parallelism in multiple channel receivers.
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Citations
52 Claims
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1. A method for preamble detection in digital data receivers, comprising the steps of:
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providing a power estimation means for producing a value of modulation power where;
powerk=abs(real(Rk)·
real(Rk-N))+abs(imag(Rk)·
imag(Rk-N)). - View Dependent Claims (2)
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3. A preamble detector for OPSK, comprising:
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an input for receiving digitized input I and Q samples, wherein said input I and Q samples represent a reconstructed base band form of QPSK modulation;
a carrier derotation means for aligning said incoming signal phases with I and Q axes;
sign means for producing a ‘
1’
if said I and Q samples are greater than or equal to 0, or a ‘
0’
if said samples are less than 0;
sample delay means for providing chains of N-sample delays to yield one symbol-length delay for both I and Q;
a differential decoder for combining a current symbol state with a prior symbol state to yield a differentially decoded symbol value;
a multiplexer for alternating between a least-significant and a most-significant bit of said differentially decoded symbol values; and
a preamble shift register containing a serial-sequential representation of a received data stream. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10, 11)
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12. A differential preamble detector for QPSK, comprising:
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an input for receiving digitized input I and Q samples;
delay means for yielding one-symbol delayed versions of both signals;
at least one multiplier for computing partial products of said I and Q samples and a complex conjugate of a delayed signal, yielding phase component real(Zk), without computing imag(Zk), with regard to a differential phase function;
real(Zk)=real(Rk)·
real(Rk-N)+imag(Rk)·
imag(Rk-N);
an adder for summing said phase components to yield a differential phase sample real(Zk);
sign means for producing a differential phase bit that flags 0-degree relative phase shifts with a ‘
1,’ and
180-degree samples with a ‘
0;
’said phase bits being sequentially clocked into a preamble shift register in the form of a serially-concatenated phase sequence; and
exclusive OR means for exclusive-ORing a nominal preamble phase sequence with a receive phase sequence. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
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21. In a QPSK transmission system, a preamble detector comprising:
means for reducing all four QPSK states to a 1-bit representation which differentiates between two antipodal states. - View Dependent Claims (22)
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23. A preamble detector, comprising:
power threshold detection means for ensuring that non-antipodal signal transitions are not identified as valid antipodal preamble transitions.
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24. A power estimator, comprising:
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an absolute value operator for forcing positive real and imaginary phase components of real(Zk) with regard to a modulation power function;
powerk=abs(real(Rk)·
real(Rk-N))+abs(imag(Rk)·
imag(Rk-N))and an adder summing said positive phase components to create a received signal power estimate. - View Dependent Claims (25, 26)
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27. An apparatus for preamble detection in digital data receivers, comprising:
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power estimation means for producing a value of modulation power, wherein;
powerk=abs(real(Rk)·
real(Rk-N))+abs(imag(Rk)·
imag(Rk-N)). - View Dependent Claims (28)
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29. A preamble detection method for QPSK, comprising the steps of:
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receiving digitized input I and Q samples, wherein said input I and Q samples represent a reconstructed base band form of QPSK modulation;
aligning said incoming signal phases with I and Q axes;
producing a ‘
1’
if said I and Q samples are greater than or equal to 0, or a ‘
0’
if said samples are less than 0;
providing chains of N-sample delays to yield one symbol-length delay for both I and Q;
combining a current symbol state with a prior symbol state to yield a differentially decoded symbol value;
alternating between a least-significant and a most-significant bit of said differentially decoded symbol values; and
providing a serial-sequential representation of a received data stream. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37)
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38. A differential preamble detection method for QPSK, comprising the steps of:
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receiving digitized input I and Q samples;
providing one-symbol delayed versions of both signals;
computing partial products of said I and Q samples and a complex conjugate of a delayed signal, yielding phase components of real(Zk), without computing imag(Zk), with regard to a differential phase function;
real(Zk)=abs(real(Rk)·
real(Rk-N))+abs(imag(Rk)·
imag(Rk-N)).summing said phase components to yield a differential phase sample real(Zk);
producing a differential phase bit that flags 0-degree relative phase shifts with a ‘
1,’ and
180-degree samples with a ‘
0;
’sequentially clocking said phase bits into a preamble shift register in the form of a serially-concatenated phase sequence; and
exclusive-ORing a nominal preamble phase sequence with a receive phase sequence. - View Dependent Claims (39, 40, 41, 42, 43, 44, 45, 46)
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47. In a QPSK transmission system, a preamble detection method comprising the step of:
reducing all four QPSK states to a 1-bit representation which differentiates between two antipodal states. - View Dependent Claims (48)
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49. A preamble detection method, comprising the step of:
providing power threshold detection means for ensuring that non-antipodal signal transitions are not identified as valid antipodal preamble transitions.
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50. A power estimation method, comprising the steps of:
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using an absolute value operator for forcing positive real and imaginary phase components of real(Zk) with regard to a modulation power function;
powerk=abs(real(Rk)·
real(Rk-N))+abs(imag(Rk)·
imag(Rk-N))and summing said positive phase components to create a received signal power estimate. - View Dependent Claims (51, 52)
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Specification