Method and apparatus for providing higher order modulation that is backwards compatible with quaternary phase shift keying (QPSK) or offset quaternary phase shift keying (OQPSK)
First Claim
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1. An apparatus for providing an asymmetrical backward compatible signal, comprising:
- a timing error accumulator coupled to a first bit stream, said first bit stream including content that is common to a QPSK/OQPSK receiver and to a PSK/QAM receiver;
a phase error accumulator coupled to a second bit stream, said phase error accumulator adjusting the phase of symbols in said second bit stream;
a phase and timing error compensator coupled to said phase error accumulator and said timing error accumulator, said phase and timing error compensator adjusts said first and second bit streams received from said phase error accumulator and said timing error accumulator to reduce timing and phase errors; and
a higher order modulator coupled to said phase and timing error compensator, said higher order modulator processing said first and said second bit streams to provide said asymmetrical backward compatible signal, wherein a signal constellation associated with said asymmetrical backward compatible modulation signal is expanded to achieve a higher throughput for said asymmetrical backward compatible modulated signal by arranging each symbol associated with said asymmetrical backward compatible signal into a cluster, wherein said cluster corresponds to a point where at least one of the conditions y=x and y=−
x exist, said x, −
x and y corresponds to points proximate an axis in a two dimensional plane.
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Abstract
A method and apparatus for providing an asymmetrical backwards compatible communications signal that is capable of being decoded by QPSK and OQPSK receivers as well as PSK and QAM receivers is provided. The invention comprises a timing error accumulator coupled to a first bit stream. The first bit stream includes content that is common to the QPSK/OQPSK receiver and to the PSK/QAM receiver. A phase error accumulator is coupled to a second bit stream and adjusts the phase of symbols in the second bit stream. A phase and timing error compensator is coupled to the phase error accumulator and the timing error accumulator and adjusts the first and second bit streams received from the phase error accumulator and the timing error accumulator in order to reduce timing and phase errors. A higher order modulator coupled to the phase and timing error compensator is also provided. The higher order modulator processes the first and second bit streams to provide the asymmetrical backwards compatible signal.
20 Citations
26 Claims
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1. An apparatus for providing an asymmetrical backward compatible signal, comprising:
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a timing error accumulator coupled to a first bit stream, said first bit stream including content that is common to a QPSK/OQPSK receiver and to a PSK/QAM receiver; a phase error accumulator coupled to a second bit stream, said phase error accumulator adjusting the phase of symbols in said second bit stream; a phase and timing error compensator coupled to said phase error accumulator and said timing error accumulator, said phase and timing error compensator adjusts said first and second bit streams received from said phase error accumulator and said timing error accumulator to reduce timing and phase errors; and a higher order modulator coupled to said phase and timing error compensator, said higher order modulator processing said first and said second bit streams to provide said asymmetrical backward compatible signal, wherein a signal constellation associated with said asymmetrical backward compatible modulation signal is expanded to achieve a higher throughput for said asymmetrical backward compatible modulated signal by arranging each symbol associated with said asymmetrical backward compatible signal into a cluster, wherein said cluster corresponds to a point where at least one of the conditions y=x and y=−
x exist, said x, −
x and y corresponds to points proximate an axis in a two dimensional plane. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A method of providing a backward compatible modulated signal, comprising:
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modulating a first and second input signal at a transmitter to obtain said backward compatible modulated signal, said backward compatible modulated signal comprises a first output signal and a second output signal; expanding at said transmitter a signal constellation associated with said backward compatible modulation signal to achieve a higher throughput for said backward compatible modulated signal by arranging each symbol associated with said backward compatible signal into a cluster, wherein said cluster corresponds to a point where at least one of the conditions y=x and y=−
x exist, said x, −
x and y corresponds to points proximate an axis in a two dimensional plane;providing said backward compatible modulated signal to a first receiver and a second receiver, demodulating at said first receiver said first output signal, wherein said first output signal includes content common to said first receiver and said second receiver; and demodulating at said second receiver said second output signal based on content contained in said first output signal. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26)
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Specification
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Current AssigneeDIRECTV, LLC (AT&T, Inc.)
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Original AssigneeThe DIRECTV Group, Inc. (AT&T, Inc.)
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InventorsSun, Feng-Wen, Lee, Lin-Nan, Eroz, Mustafa, Jiang, Yimin
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Primary Examiner(s)Payne; David C.
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Assistant Examiner(s)Bolourchi; Nader
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Application NumberUS10/142,703Publication NumberTime in Patent Office1,929 DaysField of Search375/269, 375/279, 375/280, 375/281, 375/261, 375/298, 375/300, 375/308, 375/329, 375/332US Class Current375/329CPC Class CodesH04L 27/183 Multiresolution systemsH04L 27/3488 Multiresolution systems
