Method to minimize compatibility error in hierarchical modulation using variable phase
First Claim
1. A method of transmitting digital data in a hierarchical transmission system comprising the steps of:
- providing at least a first digital data stream and a second digital data stream;
providing a non-binary, pseudo-random encoding of the second digital data stream but not the first digital data stream;
hierarchically modulating a carrier to produce a signal with a first modulation based on the first digital data stream and a second modulation based on at least the non-binary, pseudo-random encoded second digital data stream; and
transmitting the signal, whereby the transmitted signal when received may be fully demodulated for the second digital data stream or partially demodulated on the first modulation alone for the first digital data stream with the second modulation appearing as pseudo-Gaussian noise.
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Abstract
The present invention provides a method of hierarchically modulating first and second digital data streams in a broadcast system such as an SDAR system that is compatible with legacy receivers. The second digital data stream, but not the first, is provided with a non-binary pseudo-random encoding. A carrier is first modulated, e.g. QPSK, by the first digital data stream; and a second modulation is performed with the encoded second digital data stream. The encoding includes a multiplication of a matrix formed of 2, 3 or 4 consecutive bits of the secondary data stream by a matrix, e.g. a Hadamard matrix to form a product matrix having non-binary values that are used to modify consecutive symbols of the first modulation. The second modulation appears as Gaussian noise to legacy receivers over time.
31 Citations
17 Claims
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1. A method of transmitting digital data in a hierarchical transmission system comprising the steps of:
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providing at least a first digital data stream and a second digital data stream;
providing a non-binary, pseudo-random encoding of the second digital data stream but not the first digital data stream;
hierarchically modulating a carrier to produce a signal with a first modulation based on the first digital data stream and a second modulation based on at least the non-binary, pseudo-random encoded second digital data stream; and
transmitting the signal, whereby the transmitted signal when received may be fully demodulated for the second digital data stream or partially demodulated on the first modulation alone for the first digital data stream with the second modulation appearing as pseudo-Gaussian noise. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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Specification