Method and apparatus for interleaving low density parity check (ldpc) codes over mobile satellite channels

Abstract

Systems, methods and apparatus are described to interleave LDPC coded data for reception over a mobile communications channel, such as, for example, a satellite channel. In exemplary embodiments of the present invention, a method for channel interleaving includes segmenting a large LDPC code block into smaller codewords, randomly shuffling the code segments of each codeword and then convolutionally interleaving the randomly shuffled code words. In exemplary embodiments of the present invention, such random shuffling can guarantee that no two consecutive input code segments will be closer than a defined minimum number of code segments at the output of the shuffler. In exemplary embodiments of the present invention, by keeping data in, for example, manageable sub-sections, accurate SNR estimations, which are needed for the best possible LDPC decoding performance, can be facilitated based on, for example, iterative bit decisions.

1 - 24 . (canceled) 
     
     
         25 . A method of interleaving Low Density Parity Check (LDPC) codes over mobile satellite channels, comprising:
 segmenting a LDPC code block into smaller subsections, each subsection having multiple segments;   randomly shuffling the segments in each subsection;   convolutionally interleaving the subsections; and   transmitting the interleaved subsections over a satellite channel to a mobile receiver.   
     
     
         26 . The method of  claim 25 , wherein at least one of:
 the convolutionally interleaving achieves at least a defined minimum time dispersion, or   the random shuffling guarantees that no two consecutive input segments of a subsection will be closer than a defined number of segments at the output of the shuffler.   
     
     
         27 . The method of  claim 25 , wherein the subsections are some small percentage of the code block's size. 
     
     
         28 . The method of  claim 25 , wherein said convolutionally interleaving includes applying an entire subsection to each arm of a convolutional interleaver. 
     
     
         29 . A system, comprising:
 an LDPC encoder arranged to segment an LDPC code block into smaller code words, each codeword having multiple code segments;   a random shuffler arranged to shuffle segments within each codeword; and   a convolutional interleaver.   
     
     
         30 . The system of  claim 29 , wherein the convolutional interleaver has one branch for each subsection of data. 
     
     
         31 . The system of  claim 29 , wherein the random shuffler is an S-random shuffler. 
     
     
         32 . The system of  claim 31 , wherein said S-random shuffler is designed to guarantee that no two consecutive input segments of a subsection will be closer than a defined number of segments. 
     
     
         33 . The system of  claim 29 , wherein said random shuffler is designed to guarantee that no two consecutive input segments of a subsection will be closer than Y segments at the output of the shuffler, where Y is approximately equal to [Sqrt (X)]/2, where X=total number of segments. 
     
     
         34 . The system of  claim 29 , wherein the convolutional interleaver has one branch for each segment of data. 
     
     
         35 . The method of  claim 25 , wherein said random shuffler is configured to guarantee that no two consecutive input segments will be closer than Y segments at the output of the shuffler, where Y is approximately equal to [Sqrt (X)]/2, where X=total number of segments. 
     
     
         36 . The method of  claim 25 , wherein the readout order of said random shuffler is at least one of controlled by a lookup table and different for each code block within a defined number of code blocks. 
     
     
         37 . The method of  claim 36 , wherein said lookup table can repeat itself after every transmission frame. 
     
     
         37 . The system of  claim 29 , wherein the readout order of said random shuffler is at least one of controlled by a lookup table and different for each code block within a defined number of code blocks. 
     
     
         38 . The system of  claim 37 , wherein said lookup table can repeat itself after every transmission frame. 
     
     
         39 . A receiver comprising:
 a receiver configured to receive a stream of codewords;   a de-interleaver, configured to de-interleave code segments from various codewords;   a de-shuffler; and   an LDPC decoder configured to first estimate a noise variance for each code segment based on traditional noise variance cluster estimates.   
     
     
         40 . The receiver of  claim 40 , wherein the noise variance for each code segment is re-calculated on every iteration of the LDPC decoder. 
     
     
         41 . The receiver of  claim 39 , wherein the interleaved code segments from the various code words evidence at least a defined minimum time dispersion. 
     
     
         42 . The receiver of  claim 39 , wherein the code segments   
     
     
         43 . The receiver of  claim 42 , wherein said convolutionally interleaved code segments are the result of applying an entire subsection to each arm of a convolutional interleaver.