Communication methods and apparatus based on orthogonal hadamard-based sequences having selected correlation properties
First Claim
1. A method of determining a scrambling code group for a received signal in a digital communication system, in which signals are scrambled by respective scrambling codes, the scrambling codes are assigned to respective scrambling code groups, identities of the scrambling code groups are encoded in the signals by respective code-word-wise cyclically distinct sequences of signed code words, the method comprising the steps of:
- correlating the received signal to each of a plurality of the code words, wherein the code words are S-Hadamard sequences;
coherently combining the correlations in accordance with cyclic shifts of each of a plurality of sequences of signs; and
determining a maximal coherently combined correlation to identify the scrambling code group for the received signal.
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Accused Products
Abstract
Methods and apparatus for synchronization of a transmitter and a receiver are based on orthogonal sequences having optimized correlation properties. The transmitter may generate signed versions of S-Hadamard sequences that are obtained by position-wise scrambling a set of Walsh-Hadamard sequences with a special sequence having complex elements of constant magnitude. The receiver estimates a time location and sequence identity of a received version of the synchronization signal.
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Citations
44 Claims
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1. A method of determining a scrambling code group for a received signal in a digital communication system, in which signals are scrambled by respective scrambling codes, the scrambling codes are assigned to respective scrambling code groups, identities of the scrambling code groups are encoded in the signals by respective code-word-wise cyclically distinct sequences of signed code words, the method comprising the steps of:
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correlating the received signal to each of a plurality of the code words, wherein the code words are S-Hadamard sequences;
coherently combining the correlations in accordance with cyclic shifts of each of a plurality of sequences of signs; and
determining a maximal coherently combined correlation to identify the scrambling code group for the received signal. - View Dependent Claims (2)
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3. A method of determining a scrambling code group for a received signal in a digital communication system, in which signals are scrambled by respective scrambling codes, the scrambling codes are assigned to respective scrambling code groups, identities of the scrambling code groups are encoded in the signals by respective code-word-wise cyclically distinct sequences of code words, the method comprising the steps of:
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correlating the received signal to cyclic shifts of each of a plurality of sequences of code words, wherein the code words are S-Hadamard sequences;
combining the correlations for each of the plurality of sequences of code words; and
determining a maximal combined correlation to identify the scrambling code group for the received signal. - View Dependent Claims (4, 5, 6)
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7. A digital radio transmission system having at least one transmitter and at least one receiver, comprising:
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means in the transmitter for generating a synchronization signal that includes signed versions of S-Hadamard sequences, wherein the S-Hadamard sequences correspond to members of a first set of Walsh-Hadamard sequences position-wise scrambled with a special sequence having complex elements of constant magnitude;
means in the receiver for estimating a time location and sequence identity of a received version of the synchronization signal. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A method of determining a time location of a received signal and identifying a Walsh-Hadamard sequence encoded as a S-Hadamard sequence included in the received signal, wherein the S-Hadamard sequence is a product of the Walsh-Hadamard sequence and a special sequence having complex elements of constant magnitude and the Walsh-Hadamard sequence is a member of a first set of Walsh-Hadamard sequences, comprising the steps of:
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forming a position-wise product of the received signal and the special sequence; and
correlating the product with each of a plurality of Walsh-Hadamard sequences for identifying the Walsh-Hadamard sequence encoded in the received signal. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24)
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25. A method of communicating an identity of a scrambling code group for a transmitted signal in a digital communication system, in which signals are scrambled by respective scrambling codes and the scrambling codes are assigned to respective scrambling code groups, comprising the steps of:
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providing at least one S-Hadamard sequence; and
encoding the identity of the scrambling code group in the transmitted signal as a code-word-wise cyclically distinct sequence of signed S-Hadamard sequences. - View Dependent Claims (26)
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27. A method of communicating an identity of a scrambling code group for a transmitted signal in a digital communication system, in which signals are scrambled by respective scrambling codes and the scrambling codes are assigned to respective scrambling code groups, comprising the steps of:
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providing a plurality of S-Hadamard code words; and
encoding the identity of the scrambling code group in the transmitted signal as a code-word-wise cyclically distinct sequence of the S-Hadamard code words. - View Dependent Claims (28)
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29. A signal generator in a radio transmitter, comprising:
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a special sequence generator that produces a special sequence having complex elements of constant magnitude;
an S-Hadamard sequence generator that receives the special sequence and that produces at least one S-Hadamard sequence based on the special sequence, wherein S-Hadamard sequences correspond to respective members of a set of Walsh-Hadamard sequences position-wise scrambled with the special sequence;
an identity generator that produces a scrambling code group identity;
a selector that selects an S-Hadamard sequence produced by the S-Hadamard sequence generator based on the scrambling code group identity;
a combiner that combines the S-Hadamard sequence selected by the selector with an information signal, forming a combined signal. - View Dependent Claims (30, 31, 32, 33)
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34. An apparatus for use in determining a scrambling code group for a received signal in a digital communication system, in which signals are scrambled by respective scrambling codes, the scrambling codes are assigned to respective scrambling code groups, identities of the scrambling code groups are encoded in the signals by respective code words, the apparatus comprising:
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an S-Hadamard code word generator that produces at least one S-Hadamard code word based on a special sequence, wherein S-Hadamard code words correspond to respective members of a set of Walsh-Hadamard sequences position-wise scrambled with the special sequence; and
a decorrelator, wherein the decorrelator forms at least one correlation of the received signal with at least one S-Hadamard code word produced by the S-Hadamard code word generator. - View Dependent Claims (35, 36, 37, 38, 39)
a primary decorrelator that forms consecutive correlations of the received signal with a plurality of shorter sequences that correspond to position-wise multiplications of the special sequence and a subsequence of a member of the set of Walsh-Hadamard sequences; and
a secondary decorrelator that forms correlations of the consecutive correlations formed by the primary decorrelator with members of a set of Walsh-Hadamard sequences that includes the subsequence.
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37. The apparatus of claim 36, wherein the secondary decorrelator is a Fast Walsh Transform processor.
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38. The apparatus of claim 36, further comprising a multiplier that forms a product of the received signal and the special sequence, producing a descrambled received signal, and wherein the primary decorrelator forms consecutive correlations of the descrambled received signal with a subsequence of a member of the set of Walsh-Hadamard sequences.
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39. The apparatus of claim 38, wherein the primary and secondary decorrelators are a Fast Walsh Transform processor.
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40. An apparatus for use in determining a scrambling code group for a received signal in a digital communication system, in which signals are scrambled by respective scrambling codes, the scrambling codes are assigned to respective scrambling code groups, identities of the scrambling code groups are encoded in the signals by respective code words, the apparatus comprising:
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a special sequence generator that produces a special sequence having complex elements of constant magnitude;
a multiplier that forms a product of the received signal and the special sequence, producing a descrambled received signal;
a Walsh-Hadamard sequence generator that produces at least one Walsh-Hadamard sequence; and
a decorrelator, wherein the decorrelator forms at least one correlation of the descrambled received signal with at least one Walsh-Hadamard sequence produced by the Walsh-Hadamard sequence generator. - View Dependent Claims (41, 42, 43, 44)
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Specification