Method and apparatus for efficient preamble detection in digital data receivers
First Claim
Patent Images
1. A preamble detector for QPSK, comprising:
- 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.
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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.
139 Citations
18 Claims
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1. A preamble detector for QPSK, 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 (2, 3, 4, 5, 6, 7, 8, 9)
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10. 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 (11, 12, 13, 14, 15, 16, 17, 18)
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Specification