IPC분류정보
국가/구분 |
United States(US) Patent
등록
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국제특허분류(IPC7판) |
|
출원번호 |
UP-0286497
(2005-11-23)
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등록번호 |
US-7555696
(2009-07-09)
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발명자
/ 주소 |
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출원인 / 주소 |
- General Instrument Corporation
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대리인 / 주소 |
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인용정보 |
피인용 횟수 :
12 인용 특허 :
6 |
초록
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Method, apparatus, and computer readable medium for forward error correction (FEC) in a content distribution system is described. One aspect of the invention relates to encoding frames of content. In one example, each frame is set partitioned into un-coded bits and bits to be encoded. For each frame
Method, apparatus, and computer readable medium for forward error correction (FEC) in a content distribution system is described. One aspect of the invention relates to encoding frames of content. In one example, each frame is set partitioned into un-coded bits and bits to be encoded. For each frame, parity bits are computed for the bits to be encoded using low density parity check (LDPC) coding to generate a codeword having information bits and the parity bits. Groups of interleaved bits from the information bits in the codeword are generated. Symbols formed from the bit groups and the un-coded bits are pseudorandomly interleaved. The symbols are then mapped to points in a quadrature amplitude modulation (QAM) constellation.
대표청구항
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What is claimed is: 1. A method of encoding frames of content, comprising: set partitioning each frame into un-coded bits and bits to be encoded; and for each frame: applying a low density parity check (LDPC) code to the bits to be encoded to generate a codeword having information bits and parity b
What is claimed is: 1. A method of encoding frames of content, comprising: set partitioning each frame into un-coded bits and bits to be encoded; and for each frame: applying a low density parity check (LDPC) code to the bits to be encoded to generate a codeword having information bits and parity bits; generating groups of interleaved bits from bits in the codeword; pseudorandomly interleaving symbols formed from the groups of interleaved bits and the un-coded bits; and mapping the symbols to points in a quadrature amplitude modulation (QAM) constellation. 2. The method of claim 1, wherein the applying step comprises, for each bit of the bits to be encoded: accumulating the bit at accumulators associated with parity check equations, where an index of each of the accumulators with respect to the parity check equations is defined in accordance with: [x+(j)mod(Nc)Q]mod(N-K ), where x is a seed value selected from a table of seed values, j is an index of the bit with respect to the bits to be encoded, Nc is equal to 600, Q is equal to 18, N is equal to 64,800, K is equal to 54,000, and mod denotes a modulus operation. 3. The method of claim 2, wherein a parity check matrix for the codeword has 9600 columns of weight 12, 44,000 columns of weight 3, 10,799 columns of weight of weight 2, and one column of weight 1. 4. The method of claim 1, wherein the information bits comprise four bits for each of the symbols, and wherein the un-coded bits comprise log2(M)-4 bits for each of the symbols, where M is a number of the points in the QAM constellation. 5. The method of claim 4, where M is greater than or equal to 64. 6. The method of claim 1, wherein each of the groups of interleaved bits comprises four bits. 7. The method of claim 1, wherein the points in the QAM constellation are Gray-coded and set partitioned. 8. The method of claim 1, where the frames of content comprise transport stream packets, and wherein the method further comprises: computing parity bits for each of the transport stream packets using one of block coding or erasure coding. 9. Apparatus for encoding frames of content, comprising: a data parser for set partitioning each frame into un-coded bits and bits to be encoded; an encoder for applying a low density parity check (LDPC) code to the bits to be encoded for each frame to generate a codeword for each frame, the codeword having information bits and parity bits; a bit interleaver/grouper for generating groups of interleaved bits from the information bits in the codeword for each frame; and an interleaver/quadrature amplitude modulation (QAM) mapper for pseudorandomly interleaving symbols formed from the groups of interleaved bits and the un-coded bits in each frame and mapping the symbols to points in a QAM constellation for each frame. 10. The apparatus of claim 9, wherein the encoder is configured to, for each bit of the bits to be encoded in each frame: accumulate the bit at accumulators associated with parity check equations, where an index of each of the accumulators with respect to the parity check equations is defined in accordance with: [x+(j)mod(Nc)Q]mod(N-K ), where x is a seed value selected from a table of seed values, j is an index of the bit with respect to the bits to be encoded, Nc is equal to 600, Q is equal to 18, N is equal to 64,800, K is equal to 54,000, and mod denotes a modulus operation. 11. The apparatus of claim 10, wherein a parity check matrix for the codeword in each frame has 9600 columns of weight 12, 44,000 columns of weight 3, 10,799 columns of weight of weight 2, and one column of weight 1. 12. The apparatus of claim 9, wherein the information bits comprise four bits for each of the symbols in each frame, and wherein the un-coded bits comprise log2(M)-4 bits for each of the symbols in each frame, where M is a number of the points in the QAM constellation. 13. The apparatus of claim 12, where M is greater than or equal to 64. 14. The apparatus of claim 9, wherein each of the groups of interleaved bits comprises four bits. 15. The apparatus of claim 9, wherein the points in the QAM constellation are Gray-coded and set partitioned. 16. The apparatus of claim 9, where the frames of content comprise transport stream packets, and wherein the apparatus further comprises: an outer code module for computing parity bits for each of the transport stream packets using one of block coding or erasure coding.
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