# US 2014/0153672 A1 · Enhanced decoding and demapping method and apparatus for qam data signals

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- Number: US 2014/0153672 A1
- Document ID: US20140153672A1
- Status: Published application
- Kind: A1
- Application number: 13/946,706
- Filed: 2013-07-19
- Published: 2014-06-05
- Earliest claimed: 2012-12-03
- Assignees: QUALCOMM Incorporated
- Applicants: QUALCOMM Incorporated
- Inventors: Lu Zhao; Stefan Brueck; Stephan Schlupkothen; Muhammad Awais Amin; Juan Montojo; Marc W. Werner; Hendrik Schoeneich
- Web page: https://patentgrep.com/patent/US20140153672A1

## CPC

- H04L 27/06: Demodulator circuits; Receiver circuits
- H04L 1/005: {Iterative decoding, including iteration between signal detection and decoding operation}
- H04L 1/0057: {Block codes (H04L1/0061, H04L1/0064 take precedence)}
- H04L 27/3416: {in which the information is carried by both the individual signal points and the subset to which the individual points belong, e.g. using coset coding, lattice coding, or related schemes}
- H04L 1/0036: {arrangements specific to the receiver}
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

A receiver circuit, including a multi-stage QAM de-mapper, for receiving a QAM data signal is disclosed. A first de-mapper circuit recovers a set of encoded data bits from the QAM data signal by calculating a plurality of distances between a received QAM symbol and each of a plurality of possible constellation points. A second de-mapper circuit then generates a set of unencoded data bits for the received QAM symbol based, at least in part, on the plurality of distances calculated by the first de-mapper circuit. The receiver circuit may further include a decoder circuit to decode the set of encoded data bits recovered by the first de-mapper circuit. The second de-mapper circuit may identify a subset of the plurality of possible constellation points based on a result of the decoding and select a constellation point that is associated with the shortest distance of the plurality of distances.

## Claims

### Claim 1

A receiver circuit to receive a quadrature amplitude modulation (QAM) data signal, the receiver circuit comprising:
a first de-mapper circuit to recover a set of encoded data bits from the QAM data signal by calculating a plurality of distances between a received QAM symbol and each of a plurality of possible constellation points; and
a second de-mapper circuit to generate a set of un-encoded data bits for the received QAM symbol based, at least in part, on the plurality of distances calculated by the first de-mapper circuit.

### Claim 2 (depends on 1)

The receiver circuit of claim 1, further comprising:
a decoder circuit to decode the set of encoded data bits recovered by the first de-mapper circuit.

### Claim 3 (depends on 2)

The receiver circuit of claim 2, wherein the second de-mapper circuit is to generate the set of un-encoded data bits based on a result of the decoding and the plurality of distances calculated by the first de-mapper circuit.

### Claim 4 (depends on 3)

The receiver circuit of claim 3, wherein the set of encoded data bits corresponds to a low density parity check (LDPC) codeword, and wherein the result of the decoding includes a set of information bits and a set of parity bits.

### Claim 5 (depends on 4)

The receiver circuit of claim 4, wherein the set of information bits and the set of parity bits represent least significant bits (LSBs) of the received QAM symbol.

### Claim 6 (depends on 5)

The receiver circuit of claim 5, wherein the second de-mapper circuit is to identify a subset of the plurality of possible constellation points that include the LSBs.

### Claim 7 (depends on 6)

The receiver circuit of claim 6, wherein the second de-mapper circuit is to generate the set of un-encoded data bits by selecting, from the subset of possible constellation points, a constellation point that is associated with the shortest distance of the plurality of distances.

### Claim 8 (depends on 7)

The receiver circuit of claim 7, wherein the set of un-encoded data bits corresponds to the most significant bits (MSBs) of the selected constellation point.

### Claim 9 (depends on 3)

The receiver circuit of claim 3, wherein the second de-mapper circuit is selectively operable in a first mode or a second mode, and wherein:
when operating in the first mode, the second de-mapper circuit is to recover the set of un-encoded data bits concurrently with the first de-mapper circuit recovering the set of encoded data bits; and
when operating in the second mode, the second de-mapper circuit is to generate the set of un-encoded data bits after receiving the information about the plurality of distances calculated by the first de-mapper circuit and the result of the decoding.

### Claim 10 (depends on 9)

The receiver circuit of claim 9, further comprising:
a noise detector to detect noise in the QAM data signal and to select either the first mode or the second mode based on the detected noise.

### Claim 11 (depends on 10)

The receiver circuit of claim 10, wherein the noise detector selects the second mode if the detected noise is above a first threshold level.

### Claim 12

A method of de-mapping a QAM data signal, the method comprising:
recovering a set of encoded data bits from the QAM data signal by calculating a plurality of distances between a received QAM symbol and each of a plurality of possible constellation points; and
generating a set of un-encoded data bits for the received QAM symbol based, at least in part, on the plurality of distances.

### Claim 13 (depends on 12)

The method of claim 12, wherein generating the set of un-encoded data bits comprises:
decoding the set of encoded data bits; and
generating the set of un-encoded data bits based on a result of the decoding and the plurality of distances.

### Claim 14 (depends on 13)

The method of claim 13, wherein the set of encoded data bits corresponds to an LDPC codeword, and wherein the result of the decoding includes a set of information bits and a set of parity bits.

### Claim 15 (depends on 14)

The receiver of claim 14, wherein the set of information bits and the set of parity bits represent LSBs of the received QAM symbol.

### Claim 16 (depends on 15)

The method of claim 15, further comprising:
identifying a subset of the plurality of possible constellation points that include the LSBs.

### Claim 17 (depends on 16)

The method of claim 16, wherein generating the set of un-encoded data bits includes selecting, from the subset of constellation points, a constellation point that is associated with the shortest distance of the plurality of distances.

### Claim 18 (depends on 17)

The method of claim 17, wherein the set of un-encoded data bits corresponds to the MSBs of the selected constellation point.

### Claim 19 (depends on 12)

The method of claim 12, wherein generating the set of un-encoded data bits comprises:
detecting noise in the QAM data signal; and
selectively using the plurality of distances to generate the set of un-encoded data bits based on the detected noise.

### Claim 20 (depends on 19)

The method of claim 19, wherein selectively using the plurality of distances to generate the set of un-encoded data bits comprises:
generating the set of un-encoded data bits based on the plurality of distances if the detected noise is above a threshold level.

### Claim 21

A computer-readable storage medium containing program instructions that, when executed by a processor provided within a communications device, causes the device to:
receive a QAM data signal;
recover a set of encoded data bits from the QAM data signal by calculating a plurality of distances between a received QAM symbol and each of a plurality of possible constellation points; and
generate a set of un-encoded data bits for the received QAM symbol based, at least in part, on the plurality of distances.

### Claim 22 (depends on 21)

The computer-readable storage medium of claim 21, wherein execution of the program instructions to generate the set of un-encoded data bits causes the device to:
decode the set of encoded data bits; and
generate the set of un-encoded data bits based on a result of the decoding and the plurality of distances.

### Claim 23 (depends on 22)

The computer-readable storage medium of claim 22, wherein the set of encoded data bits corresponds to an LDPC codeword, and wherein the result of the decoding includes a set of information bits and a set of parity bits.

### Claim 24 (depends on 23)

The computer-readable storage medium of claim 23, wherein the set of information bits and the set of parity bits represent LSBs of the received QAM symbol.

### Claim 25 (depends on 24)

The computer-readable storage medium of claim 24, further comprising program instructions that cause the device to:
identify a subset of the plurality of possible constellation points that include the LSBs.

### Claim 26 (depends on 25)

The computer-readable storage medium of claim 25, wherein execution of the program instructions to generate the set of un-encoded data bits causes the device to:
select, from the subset of constellation points, a constellation point that is associated with the shortest distance of the plurality of distances.

### Claim 27 (depends on 26)

The computer-readable storage medium of claim 26, wherein the set of un-encoded data bits corresponds to the MSBs of the selected constellation point.

### Claim 28 (depends on 21)

The computer-readable storage medium of claim 21, wherein execution of the program instructions to generate the set of un-encoded data bits causes the device to:
detect noise in the QAM data signal; and
selectively use the plurality of distances to generate the set of un-encoded data bits based on the detected noise.

### Claim 29 (depends on 28)

The computer-readable storage medium of claim 28, wherein execution of the program instructions to selectively use the plurality of distances to generate the set of un-encoded data bits causes the device to:
generate the set of un-encoded data bits based on the plurality of distances if the detected noise is above a threshold level.

### Claim 30

A receiver circuit to receive a QAM data signal, the receiver circuit comprising:
means for recovering a set of encoded data bits from the QAM data signal by calculating a plurality of distances between a received QAM symbol and each of a plurality of possible constellation points; and
means for generating a set of un-encoded data bits for the received QAM symbol based, at least in part, on the plurality of distances.

### Claim 31 (depends on 30)

The receiver circuit of claim 30, wherein the means for generating the set of un-encoded data bits is to:
decode the set of encoded data bits; and
generate the set of un-encoded data bits based on a result of the decoding and the plurality of distances.

### Claim 32 (depends on 31)

The receiver circuit of claim 31, wherein the set of encoded data bits corresponds to an LDPC codeword, and wherein the result of the decoding includes a set of information bits and a set of parity bits.

### Claim 33 (depends on 32)

The receiver circuit of claim 32, wherein the set of information bits and the set of parity bits represent LSBs of the received QAM symbol.

### Claim 34 (depends on 33)

The receiver circuit of claim 33, further comprising:
means for identifying a subset of the plurality of possible constellation points that include the LSBs.

### Claim 35 (depends on 34)

The receiver circuit of claim 34, wherein the means for generating the set of un-encoded data bits is to:
select, from the subset of constellation points, a constellation point that is associated with the shortest distance of the plurality of distances.

### Claim 36 (depends on 35)

The receiver circuit of claim 35, wherein the set of un-encoded data bits corresponds to the MSBs of the selected constellation point.

### Claim 37 (depends on 30)

The receiver circuit of claim 30, wherein the means for generating the set of un-encoded data bits is to:
detect noise in the QAM data signal; and
selectively use the plurality of distances to generate the set of un-encoded data bits based on the detected noise.

### Claim 38 (depends on 37)

The receiver circuit of claim 37, wherein the means for generating the set of un-encoded data bits is to further:
generate the set of un-encoded data bits based on the plurality of distances if the detected noise is above a threshold level.