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;
generating a predetermined repeating series of n consecutive integers selected from a group of integers that is substantially smaller than n, the n consecutive integers of the series having a distribution of magnitudes across the series having an appearance of random noise;
modulating a carrier to produce a signal with a first modulation based on the first digital data stream;
hierarchically modulating the first modulation with a second modulation, the second modulation comprising modifying consecutive symbols of the first modulation by a magnitude based on the magnitude of the next consecutive one of the repeating series of n consecutive integers and a direction based on the bit value of the next consecutive bit of the 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 random noise.
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Abstract
The present invention provides a method, receiver and transmitter for use in a SDAR system. The method involves generating a first modulated signal based on first input data. Additional modulation is superimposed on the first modulated signal based on additional input data, being spread across a plurality of symbols in the first modulated signal in a predetermined pattern to generate a modified signal which is then transmitted. The modified signal is decoded by performing a first demodulation of the first modulated signal then additional demodulation is performed to obtain additional input data. The superimposing step uses a plurality of offset sequence values to add the additional modulation to the first modulated signal. The offset sequence may appear as a pseudo-random distribution of offset sequence values, and may include at least one zero offset value. Alternatively, the additional modulated signal may be a formed as a direct sequence spread spectrum modulation and the offset sequence appearing as a pseudo-noise distribution. A Hadamard matrix sequence may be used as the direct sequence code.
62 Citations
8 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;
generating a predetermined repeating series of n consecutive integers selected from a group of integers that is substantially smaller than n, the n consecutive integers of the series having a distribution of magnitudes across the series having an appearance of random noise;
modulating a carrier to produce a signal with a first modulation based on the first digital data stream;
hierarchically modulating the first modulation with a second modulation, the second modulation comprising modifying consecutive symbols of the first modulation by a magnitude based on the magnitude of the next consecutive one of the repeating series of n consecutive integers and a direction based on the bit value of the next consecutive bit of the 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 random noise. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification