Method and apparatus for decoding a data packet using scalable soft-bit retransmission combining

• US 9,130,749 B1
• Filed: 09/05/2013
• Issued: 09/08/2015
• Est. Priority Date: 09/12/2012
• Status: Active Grant

• Current Assignee: Marvell Asia Pte Limited (Marvell Technology Group Limited)
• Original Assignee: Marvell International Limited (Marvell Technology Group Limited)
• Inventors: Song, Leilei, Lou, Hui-Ling, Zhang, Zheng
• Primary Examiner(s): BRITT, CYNTHIA H
• Application Number:
  US14/019,006
• Time in Patent Office: 733 Days
• Field of Search: 714/748
• US Class Current: 1/1
• CPC Class Codes: H04L 1/0045 Arrangements at the receiver end
• CPC Class Codes: H04L 1/08 by repeating transmission, e.g. Verdan system H04L1/1858 and H04L1/189 take precedence
• CPC Class Codes: H04L 1/1812 Hybrid protocols; Hybrid automatic repeat request [HARQ]
• CPC Class Codes: H04L 1/1845 Combining techniques, e.g. code combining

Abstract

Methods and systems for decoding a data packet using soft-bit retransmission combining are provided herein. A first transmission of the data packet is received and corresponding soft information is generated. The soft information is represented by a first set of bits and a subset of those bits is stored. Subsequently, a second transmission of the data packet is received and corresponding soft information is generated. The soft information corresponding to the second transmission is represented by a second set of bits and combined with the stored subset of soft-bits corresponding to the first transmission to produce a third set of bits. At least a portion of the data packet is decoded based on the third set of bits.

Claims

1. A method for decoding a data packet, the method comprising:

receiving a first transmission of the data packet;

generating first soft information for the first transmission of the data packet, wherein the first soft information is represented by a first set of bits;

storing a subset of the first set of bits;

receiving a second transmission of the data packet;

generating second soft information for the second transmission of the data packet, wherein the second soft information is represented by a second set of bits;

combining the second set of bits with the stored subset of bits to produce a third set of bits;

decoding a portion of the data packet based on the third set of bits;

scaling the first set of bits by a scale factor prior to the storing; and

scaling the stored subset of bits by an inverse of the scale factor prior to the combining.

2. The method of claim 1, wherein the first soft information is a first log-likelihood ratio for a bit in the data packet, and wherein the second soft information is a second log-likelihood ratio for the bit.

3. The method of claim 1 further comprising:

performing a decoding operation on the first set of bits;

identifying a decoding failure during the decoding operation; and

transmitting a negative acknowledgment (NACK), wherein the second transmission of the data packet is transmitted in response to the NACK.

4. The method of claim 3 further comprising:

storing the subset of the first set of bits in response to identifying the decoding failure.

5. The method of claim 1 further comprising:

identifying an amount of available memory; and

determining a size of the subset of the first set of bits based on the amount of available memory or receiver performance.

6. The method of claim 5, wherein each of the first set of bits and the second set of bits contains 8 bits, and wherein the stored subset of bits contains 6 bits.

7. The method of claim 1, wherein the combining comprises:

determining a format of the second set of bits;

determining a format of the stored subset of bits; and

aligning the second set of bits with the stored subset of bits based on (i) the determined formats of the second set of bits and (ii) the determined format of the stored subset of bits.

8. The method of claim 1, wherein the stored subset of bits is a first stored subset of bits, and the scale factor is a first scale factor, and wherein the method further comprises:

identifying a decoding failure during the decoding;

scaling the third set of bits by a second scale factor different from the first scale factor;

storing a subset of the scaled third set of bits as a second stored subset of bits;

receiving a third transmission of the data packet;

generating third soft information for the third transmission of the data packet, wherein the third soft information is represented by a fourth set of bits;

scaling the second stored subset of bits by an inverse of the second scale factor;

combining the fourth set of bits with the scaled second stored subset of bits to produce a fifth set of bits; and

decoding a portion of the data packet based on the fifth set of bits.

9. The method of claim 1, wherein the storing comprises saturating the first set of bits to produce the subset of the first set of bits based on a desired size of the subset, and wherein the saturating comprises at least one of:

eliminating one or more high-order bits in the first set of bits; and

eliminating one or more low-order bits in the first set of bits.

11. The system of claim 1 further comprising:

a saturation unit configured to saturate the first set of bits to produce the subset of the first set of bits based on a desired size of the subset, and wherein the saturating comprises at least one of;

eliminating one or more high-order bits in the first set of bits; and

eliminating one or more low-order bits in the first set of bits.

10. A system for decoding a data packet, the system comprising:

a downlink receiver configured to;

receive a first transmission of the data packet; and

generate first soft information for the first transmission of the data packet, wherein the first soft information is represented by a first set of bits;

a memory configured to store a subset of the first set of bits;

the downlink receiver further configured to;

receive a second transmission of the data packet; and

generate second soft information for the second transmission of the data packet, wherein the second soft information is represented by a second set of bits;

a combining circuit configured to combine the second set of bits with the stored subset of bits to produce a third set of bits;

a decoder configured to decode a portion of the data packet based on the third set of bits;

a first scaling circuit configured to scale the first set of bits by a scale factor prior to the storing; and

a second scaling circuit configured to scale the stored subset of bits by an inverse of the scale factor prior to the combining.

12. The system of claim 10, wherein the stored subset of bits is a first stored subset of bits and the scale factor is a first scale factor, and wherein:

the decoder is further configured to identify a decoding failure during the decoding;

the first scaling circuit is further configured to scale the third set of bits by a second scale factor different from the first scale factor;

the memory is further configured to store a subset of the scaled third set of bits as a second stored subset of bits;

the downlink receiver is further configured to;

receive a third transmission of the data packet; and

generate third soft information for the third transmission of the data packet, wherein the third soft information is represented by a fourth set of bits;

the second scaling circuit is further configured to scale the second stored subset of bits by an inverse of the second scale factor;

the combining circuit is further configured to combine the fourth set of bits with the scaled second stored subset of bits to produce a fifth set of bits; and

the decoder is further configured to decode a portion of the data packet based on the fifth set of bits.

13. The system of claim 10, wherein the first soft information is a first log-likelihood ratio for a bit in the data packet, and wherein the second soft information is a second log-likelihood ratio for the bit.

14. The system of claim 10, wherein the decoder is further configured to:

perform a decoding operation on the first set of bits;

identify a decoding failure during the decoding operation; and

initiate a transmission of a negative acknowledgment (NACK), wherein the second transmission of the data packet is transmitted in response to the NACK.

15. The system of claim 14, wherein the memory is further configured to store the subset of the first set of bits in response to the decoding failure.

16. The system of claim 10, further comprising processing circuitry configured to:

identify an amount of available memory; and

determine a size of the subset of the first set of bits based on the amount of available memory or receiver performance.

17. The system of claim 16, wherein each of the first set of bits and the second set of bits contains 8 bits, and wherein the stored subset of bits contains 6 bits.

18. The system of claim 10, wherein the combining circuit is further configured to:

determine a format of the second set of bits;

determine a format of the stored subset of bits; and

align the second set of bits with the stored subset of bits based on (i) the determined formats of the second set of bits and (ii) the determined format of the stored subset of bits.

19. A method for decoding a data packet, the method comprising:

receiving a first transmission of the data packet;

generating first soft information for the first transmission of the data packet, wherein the first soft information is represented by a first set of bits;

storing a subset of the first set of bits;

receiving a second transmission of the data packet;

generating second soft information for the second transmission of the data packet, wherein the second soft information is represented by a second set of bits;

combining the second set of bits with the stored subset of bits to produce a third set of bits; and

decoding a portion of the data packet based on the third set of bits;

wherein the storing comprises saturating the first set of bits to produce the subset of the first set of bits based on a desired size of the subset, and wherein the saturating comprises at least one of;

eliminating one or more high-order bits in the first set of bits; and

eliminating one or more low-order bits in the first set of bits.