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US 9,036,694 B2Granted
Adaptive QAM transmission scheme to improve performance on an AWGN channel
AssigneeThomson Licensing
InventorsWei Zhou, Li Zou
Life of this patent
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Abstract
A cable transmitter supports a number of low density parity check (LDPC) coding rates, e.g., ¼, ⅓, ⅖, ½, ⅗, ⅔, ¾, ⅘, ⅚, 8/9 and 9/10; and supports a number of quadrature amplitude modulation (QAM) schemes, e.g., 4-QAM, 16-QAM, 64-QAM, 256-QAM, 1024-QAM or higher. For a selected modulation scheme, the cable transmitter selects between using a non-uniform symbol constellation or a uniform symbol constellation as a function of a selected coding rate.
Claims15
A method comprising:
- adapting a symbol constellation as a function of an error correction coding rate to be either a non-uniform symbol constellation or a uniform symbol constellation, including:
- comparing the error correction coding rate to a threshold value, where the threshold value is associated with a selected QAM modulation scheme, the QAM modulation scheme having an associated symbol constellation;
- adapting the associated symbol constellation to be non-uniform if the error correction coding rate is greater than, or equal, to the threshold value;
- and
- otherwise adapting the associated symbol constellation to be uniform if the error correction coding rate is less than the threshold value;
- and
- quadrature amplitude modulating a signal for transmission or demodulating a received signal in accordance with the adapted symbol constellation.
4 more elements
Apparatus comprising:
- a forward error correction encoder for providing encoded data having an associated error correction coding rate;
- and
- a quadrature amplitude modulator for adapting a symbol constellation as a function of the associated error correction coding rate to be either a non-uniform symbol constellation or a uniform symbol constellation and for modulating the encoded data in accordance with the adapted symbol constellation for transmission,
- wherein the quadrature amplitude modulator adapts the symbol constellation to be non-uniform if the associated error correction coding rate is greater than, or equal to, a threshold value, and otherwise adapts the symbol constellation to be uniform if the associated error correction coding rate is less than the threshold value.
1 more element
Apparatus comprising:
- a quadrature amplitude demodulator for adapting a symbol constellation as a function of an associated error correction coding rate to be either a non-uniform symbol constellation or a uniform symbol constellation and for demodulating received data in accordance with the adapted symbol constellation for providing encoded data, wherein the quadrature amplitude demodulator adapts the symbol constellation to be non-uniform if the associated error correction coding rate is greater than, or equal to, a threshold value, and otherwise adapts the symbol constellation to be uniform if the associated error correction coding rate is less than the threshold value;
- and
- a forward error correction decoder for processing the encoded data encoded at the associated error correction coding rate and for providing decoded data.
Dependencies are inferred from the claim text.