Data compression with incremental redundancy
View Patent ↗In a packet-based data transmission including incremental redundancy (IR) protocols, the memory consumption of the IR protocol is reduced by compressing and storing failed data units in their punctured format. The failed data units are compressed using low complexity compression/decompression algorithms. The compression algorithm includes two parts: calculating and storing a scale factor for each transmission burst that estimates the soft values in the burst, and storing each soft values' sign in local memory instead of the complete soft value. If the currently received data unit is a retransmission, its compressed versions in the punctured format stored in the IR memory are decompressed, de-punctured and combined with the currently received data unit. The combined data unit is then decoded. The decompression restores an estimated soft-value by multiplying the sign value stored in the IR memory with its corresponding scale factor obtained from a mapping table.
1. A method of storing failed packet data units (PDUs) in a packet-transmission system, in which the PDUs are encoded to include redundancy, and punctured according to a specified puncturing scheme prior to transmission, the method comprising:
receiving a transmission;
processing the received transmission to retrieve a PDU;
de-puncturing the PDU;
decoding the de-punctured PDU; and
if the decoded PDU contains errors, then storing the PDU and requesting retransmission.
wherein the step of storing the PDU comprises:
compressing the PDU; and
storing the compressed PDU.
2. The method of claim 1 , wherein the PDU is transmitted over a plurality of different transmission bursts.
3. The method of claim 1 , wherein the step of processing the received transmission comprises:
generating a sequence of soft-values representative of each bit in the received transmission;
calculating and storing a scale factor representative of the soft-values within the sequence; and
generating a sub-sequence of soft-values representative of a transmitted PDU.
4. The method of claim 3 , wherein the scale factor is an average of the absolute values of the soft-values within the sequence.
5. The method of claim 3 , wherein the step of compressing the PDU comprises:
storing the sign of each soft-value within the sub-sequence.
6. The method of claim 1 , wherein the PDU is compressed in its punctured format.
7. The method of claim 6 , further comprising:
determining, prior to decoding the de-punctured PDU, if there are any compressed PDUs stored in memory that correspond to the currently received, de-punctured PDU;
if there are any corresponding PDUs stored in memory then, for each corresponding PDU:
decompressing the PDU;
de-puncturing the decompressed PDU;
combining the de-punctured, decompressed PDU with the currently received, de-punctured PDU;
decoding the combined PDU; and
if the decoded combined PDU contains errors, then compressing and storing the currently received punctured PDU.
8. The method of claim 1 , wherein the PDU is compressed in its de-punctured format.
9. The method of claim 8 , further comprising:
determining, prior to decoding the de-punctured PDU, if there are any compressed PDUs stored in memory that correspond to the currently received, de-punctured PDU;
if there are any corresponding PDUs stored in memory then, for each corresponding PDU:
decompressing the PDU;
combining the decompressed PDU with the currently received, de-punctured PDU;
decoding the combined PDU; and
if the decoded combined PDU contains errors, then compressing and storing the currently received de-punctured PDU.
10. The method of claim 9 , wherein the step of processing the received transmission comprises:
generating a sequence of soft-values representative of each bit in the received transmission;
calculating and storing a scale factor representative of the soft-values within the sequence; and
generating sub-sequence of soft-values representative of a transmitted PDU.
11. The method of claim 10 , wherein the scale factor is an average of the absolute values of the soft-values within the sequence.
12. The method of claim 10 wherein the step of compressing the PDU comprises:
storing the sign of each soft-value within the sub-sequence.
13. The method of claim 12 , wherein the step of decompressing the corresponding PDU comprises:
multiplying the stored sign of each soft-value in the sub-sequence by the stored scale factor.
14. A receiver comprising:
a soft output detector configured to generate a sequence of soft-values representative of each bit within a received transmission;
a decoder;
local memory; and
a processor, the processor comprising logic configured to:
process the retrieved transmission in order to retrieve a PDU;
de-puncture the PDU; and
compress and store in the local memory the retrieved PDU if the de-punctured PDU fails the decoding process.
15. The receiver of claim 14 , wherein the processor further includes logic configured to:
determine, prior to decoding the de-punctured PDU, if there are any corresponding compressed PDUs stored in memory;
for each stored PDU the logic is configured to:
decompress the PDU;
de-puncture the decompressed PDU;
combine the de-punctured, decompressed, PDU with the currently received de-punctured PDU; and
compress and store the retrieved PDU, if the decoded combined PDU fails the decoding process.
16. A computer-readable storage medium having stored therein one or more instructions that cause a processor to perform the steps of:
processing a received transmission to retrieve a PDU;
de-puncturing the PDU;
decoding the de-punctured PDU; and
if the decoded PDU contains errors, then compressing and storing the punctured PDU.
17. The computer-readable storage medium of claim 16 , further comprising one or more instructions that cause a processor to perform the steps of:
determining, prior to decoding the de-punctured PDU, if there are any corresponding compressed PDUs stored in memory;
if there are compressed PDUs stored in memory then, for each compressed PDU:
decompressing the PDU;
de-puncturing the decompressed PDU;
combining the de-punctured, decompressed, PDU with the currently received, de-punctured PDU;
decoding the combined PDU; and
if the decoded combined PDU contains errors, then compressing and storing the currently received punctured PDU.