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US 7,079,585 B1Granted
Gray encoding for hierarchical QAM transmission systems
AssigneeThomson Licensing
InventorsTimothy Forrest Settle, Thomas Peter Krauss, Kumar Ramaswamy
Life of this patent
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Abstract
A hierarchical QAM system allows the transmission of different sources by embedding the relative constellation points. At the transmitter the constellations generated by the different sources are remapped by a grey coder and then combined. At the receiver, the different source data are decoded by using a corresponding grey code demapper.
Claims16
A hierarchical QAM transmission system, comprising:
- a source of data symbols (DATA 1, DATA2), each representing a multibit binary value;
- a hierarchical QAM transmitter (102, 104, 106, 108, 110, 111), responsive to the value of a data symbol for transmitting one of a constellation of data points in the I-Q plane, each data point in the constellation associated with a respective value of a symbol such that symbol values of adjoining constellation data points differ by no more than one bit;
- and
- a hierarchical QAM receiver (302, 304, 306, 308, 310, 312), responsive to a received data point, for generating a received symbol (DATA 1′, DATA 2′), and characterized by the transmitter comprising:
- a level 1 QPSK modulator (104), responsive to a level 1 portion (DATA 1) of a data symbol, for generating respective I and Q signals representing a center point of a predetermined one of four quadrants associated with the value of the level 1 portion of the data symbol;
- a level 2 QPSK modulator (110), responsive to a level 2 portion of the data symbol (DATA2), for generating respective I and Q signals representing a center point of the predetermined one of four quadrants associated with the value of the level 2 portion of the data symbol;
- a signal combiner (106, 111;
- 106(I), 106(Q)), coupled to the level 1 modulator (104) and the level 2 modulator (110), for weighting the respective I and Q signals from the level 2 QPSK modulator (110) by a weighting factor of 0.5 and combining the weighted level 2 I and Q signals with the respective I and Q signals from the level 1 modulator;
- and
- a gray code mapper (112), coupled between the level 2 QPSK modulator (110) and the signal combiner (106, 111), for remapping the respective I and Q signals from the level 2 QPSK modulator (110) responsive to the first portion (DATA 1) of the data symbol (DATA1, DATA 2).
7 more elements
A hierarchical QAM transmitting system, comprising:
- a source of data symbols (DATA 1, DATA 2), each representing a multibit binary value;
- and
- a hierarchical QAM transmitter (102, 104, 106, 108, 110, 111), responsive to the value of a data symbol for transmitting one of a constellation of data points in the I-Q plane, each data point in the constellation associated with a respective value of a symbol such that symbol values of adjoining constellation data points differ by no more than one bit, the transmitter characterized by:
- a level 1 QPSK modulator (104), responsive to a level 1 portion (DATA 1) of a data symbol, for generating respective I and Q signals representing a center point of a predetermined one of four quadrants associated with the value of the level 1 portion (DATA 1) of the data symbol;
- a level 2 QPSK modulator (110), responsive to a level 2 portion (DATA 2) of the data symbol, for generating respective I and Q signals representing a center point of the predetermined one of four quadrants associated with the value of the level 2 portion (DATA 2) of the data symbol;
- a signal combiner (106, 111), coupled to the level 1 modulator (104) and the level 2 modulator (110), for weighting the respective I and Q signals from the level 2 QPSK modulator (110) by a weighting factor of 0.5 and combining the weighted level 2 I and Q signals with the respective I and Q signals from the level 1 modulator (104);
- and
- a gray code mapper (112), coupled between the level 2 QPSK modulator (110) and the signal combiner (106, 111), for remapping the respective I and Q signals from the level 2 QPSK modulator (110) responsive to the first portion (DATA 1) of the data symbol.
5 more elements
A hierarchical QAM receiving system comprising:
- a source (200) of a received QAM signal representing a received data point, the received data point representing a transmitted one of a constellation of data points in the I-Q plane, each transmitted data point associated with a respective value of a transmitted symbol such that symbol values of adjoining constellation data points differ by no more than one bit;
- and
- a hierarchical QAM receiver 300, responsive to the received data point, for generating a received symbol (DATA 1′, DATA 2′), and characterized by:
- a demodulator (302), for generating respective received I and Q signals representing the received data point;
- a level 1 decoder (304), responsive to the received I and Q signals, for generating a received level 1 symbol (DATA 1′);
- translating circuitry (306, 308, 310), coupled to the demodulator (302) and the level 1 decoder (304), for generating respective I and Q signals representing a received level 2 data point;
- a level 2 decoder (312), responsive to the respective I and Q signals representing the received level 2 data point, for generating respective I and Q signals representing a received level 2 symbol (DATA 2′);
- and
- a gray code mapper (314), coupled between translating circuitry (306, 308, 310) and the level 2 decoder (312), for remapping the respective I and Q signals representing the level 2 data point in response to the received level 1 symbol (DATA 1′).
6 more elements
Dependencies are inferred from the claim text.