Method to minimize compatibility error in hierarchical modulation
First Claim
1. A method for transmitting two levels of data in a hierarchical transmission system comprising the steps of:
- in a transmitter, generating a first modulated signal based on first input data;
in the transmitter, hierarchically superimposing a second modulation on selected symbols of the first modulated signal interspersed with other symbols of the first modulated signal in which no second modulation is superimposed, said superimposing creating a combined signal presenting lower apparent noise to receivers able to demodulate the first modulated signal but unable to demodulate and decode the second modulation; and
transmitting the combined signal.
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Abstract
The present invention involves a method and system for transmitting two levels of data in a hierarchical transmission schema. A first modulated signal is generated based on first input. A second modulation signal is generated based on a second input that has a data rate that is a fraction of the data rate of the first modulated signal. The second modulation signal has known instances where the second modulation signal has no energy. In a system where the first modulation is quadrature phase shift keying (QPSK), the second modulation signal can be a secondary phase offset. A receiver in the system that has a priori knowledge about the timing relationship between the first data signal and the instances when the second data signal is present will be able to detect both data signals optimally.
72 Citations
15 Claims
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1. A method for transmitting two levels of data in a hierarchical transmission system comprising the steps of:
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in a transmitter, generating a first modulated signal based on first input data; in the transmitter, hierarchically superimposing a second modulation on selected symbols of the first modulated signal interspersed with other symbols of the first modulated signal in which no second modulation is superimposed, said superimposing creating a combined signal presenting lower apparent noise to receivers able to demodulate the first modulated signal but unable to demodulate and decode the second modulation; and transmitting the combined signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for transmitting two levels of data in a hierarchical transmission system comprising the steps of:
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generating a first modulated signal based on first input data; introducing a second phase shift modulation on the first modulated signal using a zero phase shift based on second input data, said second phase shift modulation being spread across a the carrier to generate a modified signal; and transmitting the modified signal. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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Specification