Gray encoding for hierarchical QAM transmission systems

• US 7,079,585 B1
• Filed: 11/22/2000
• Issued: 07/18/2006
• Est. Priority Date: 11/23/1999
• Status: Expired due to Term

• Current Assignee: InterDigital Madison Patent Holdings (InterDigital, Inc.)
• Original Assignee: Thomson Licensing (Vantiva SA)
• Inventors: Ramaswamy, Kumar, Krauss, Thomas Peter, Settle, Timothy Forrest
• Primary Examiner(s): Tran, Khai
• Application Number:
  US10/148,223
• Time in Patent Office: 2,064 Days
• Field of Search: 375/261, 375/341, 375/298, 375/262, 329/304, 332/103
• US Class Current: 375/261
• CPC Class Codes: H04L 1/0048 in conjunction with detection of multiuser or interfering signals, e.g. iteration between CDMA or MIMO detector and FEC decoder for spatial equalizer H04L25/03286
• CPC Class Codes: H04L 27/3433 using an underlying square constellation

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.

Claims

1. 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).

2. The system of claim 1 characterized in that:

the level 1 (DATA 1) and level 2 (DATA2) portions of the data symbol (DATA 1, DATA 2) are respective sets of two bits of the multibit binary value;

the level 1 (104) and level 2 (110) modulators generate respective I and Q signals in an upper right hand quadrant of the I-Q plane if the set of two bits is 00 (0);

in an upper left hand quadrant of the I-Q plane if the set of two bits is 01 (1), in a lower right hand quadrant of the I-Q plane of the set of two bits is 10 (2), and a lower left hand quadrant of the I-Q plane if the set of two bits is 11 (3); and

the gray code mapper (112) comprises an input terminal coupled to the level 2 modulator (110) for receiving respective I and Q input signals, and an output terminal coupled to the signal combiner (106, 111) for generating respective I and Q output signals, and remaps the respective I and Q input signals to respective I and Q output signals by;

if the level 1 portion (DATA 1) of the data symbol is 0, then the I and Q output signals are equal to the I and Q input signals respectively;

if the level 1 portion (DATA 1) of the data symbol is 1, then the I output signal is equal to the negative of the I input signal, and the Q output signal is equal to the Q input signal, if the level 1 portion (DATA 1) of the data symbol is 2, then the I output signal is equal to the I input signal and the Q output signal is equal to the negative of the Q input signal, and if the level 1 portion (DATA 1) of the data symbol is 3, then the I output signal is equal to the negative of the I input signal and the Q output signal is equal to the negative of the Q input signal.

3. The system of claim 1 characterized in that the hierarchical QAM receiver comprises:

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 (DATA 2′

);

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).

4. The system of claim 3 characterized in that the translating circuitry (306, 308, 310) comprises:

a reencoder (308), coupled to the level 1 decoder (304), for generating respective I and Q signals representing the ideal center point of the quadrant of the received level 1 symbol (DATA 1); and

a subtractor (310) having a subtrahend input terminal coupled to the reencoder (308), a minuend input terminal coupled to the demodulator (302), and an difference output terminal generating the respective I and Q signals representing the received level 2 data point.

5. The system of claim 1 characterized in that the gray code mapper (314) comprises:

an input terminal coupled to the translating circuitry (306, 308, 310) for receiving respective I and Q input signals;

an output terminal coupled to the level 2 decoder (312) for generating respective I and Q output signals; and

circuitry for remapping the respective I and Q input signals to respective I and Q output signals by;

if the received level 1 symbol (DATA 1′

) is 0, then the I and Q output signals are equal to the I and Q input signals respectively;

if the received level 1 symbol (DATA 1′

) is 1, then the I output signal is equal to the negative of the I input signal, and the Q output signal is equal to the Q input signal, if the received level 1 symbol (DATA 1′

) is 2, then the I output signal is equal to the I input signal and the Q output signal is equal to the negative of the Q input signal, and if the received level 1 symbol (DATA 1′

) is 3, then the I output signal is equal to the negative of the I input signal and the Q output signal is equal to the negative of the Q input signal.

6. The system of claim 1 characterized in that:

the hierarchical QAM transmitter (100) comprises a ground station transmitting antenna;

the hierarchical QAM receiver (300) comprises a receiving antenna; and

the transmission system (200) further comprises a satellite for receiving the signal transmitted from the hierarchical QAM transmitter (100) ground station transmitting antenna and broadcasting a signal receivable by the receiving antenna of the hierarchical QAM receiver (300).

7. The system of claim 1 characterized in that the source of data symbols comprises:

a first source (DATA 1) of digital data;

a second source (DATA 2) of digital data; and

wherein the data symbol is a combination of data from the first digital data source (DATA 1) and the second digital data source (DATA 2).

8. The system of claim 7 characterized in that the first (DATA 1) and second (DATA 2) digital data sources generate respective bit streams and the data symbol is a combination of a set of two bits from the first digital data source (DATA 1) and a set of two bits from the second digital data source (DATA 2).

9. 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.

10. The transmitting system of claim 9 characterized in that:

the level 1 (DATA 1) and level 2 (DATA 2) portions of the data symbol are respective sets of two bits of the multibit binary value;

the level 1 (104) and level 2 (110) modulators both generate respective I and Q signals in an upper right hand quadrant of the I-Q plane if the set of two bits is 00 (0);

in an upper left hand quadrant of the I-Q plane if the set of two bits is 01 (1), in a lower right hand quadrant of the I-Q plane of the set of two bits is 10 (2), and a lower left hand quadrant of the I-Q plane if the set of two bits is 11 (3); and

the gray code mapper (112) comprises an input terminal coupled to the level 2 modulator (110) for receiving respective I and Q input signals, and an output terminal coupled to the signal combiner (106, 111) for generating respective I and Q output signals, and remaps the respective I and Q input signals to respective I and Q output signals by;

if the level 1 portion (DATA 1) of the data symbol is 0, then the I and Q output signals are equal to the I and Q input signals respectively;

if the level 1 portion (DATA 1) of the data symbol is 1, then the I output signal is equal to the negative of the I input signal, and the Q output signal is equal to the Q input signal, if the level 1 portion (DATA 1) of the data symbol is 2, then the I output signal is equal to the I input signal and the Q output signal is equal to the negative of the Q input signal, and if the level 1 portion (DATA 1) of the data symbol is 3, then the I output signal is equal to the negative of the I input signal and the Q output signal is equal to the negative of the Q input signal.

11. The transmitting system of claim 9 characterized in that the source of data symbols comprises:

a first source (DATA 1) of digital data; and

a second source (DATA 2) of digital data;

wherein the data symbol is a combination of data from the first digital data source (DATA 1) and the second digital data source (DATA 2).

12. The transmitting system of claim 11 characterized in that the first (DATA 1) and second (DATA 2) digital data sources generate respective bit streams and the data symbol is a combination of a set of two bits from the first digital data source (DATA 1) and a set of two bits from the second digital data source (DATA 2).

13. The transmitting system of claim 9 characterized in that the hierarchical QAM transmitter (100) further comprises a satellite ground station transmitting antenna.

14. 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′

).

15. The receiving system of claim 14 characterized in that the gray code mapper (314) comprises an input terminal coupled to the translating circuitry (306, 308, 310) for receiving respective I and Q input signals, and an output terminal coupled to the level 2 decoder (312) for generating respective I and Q output signals, and remaps the respective I and Q input signals to respective I and Q output signals by:

if the received level 1 symbol (DATA 1′

) is 0, then the I and Q output signals are equal to the I and Q input signals respectively;

if the received level 1 symbol (DATA 1′

) is 1, then the I output signal is equal to the negative of the I input signal, and the Q output signal is equal to the Q input signal, if the received level 1 symbol (DATA 1′

) is 2, then the I output signal is equal to the I input signal and the Q output signal is equal to the negative of the Q input signal, and if the received level 1 symbol (DATA 1′

) is 3, then the I output signal is equal to the negative of the I input signal and the Q output signal is equal to the negative of the Q input signal.

16. The receiving system of claim 14 wherein the QAM signal source (200) comprises a satellite receiving antenna.