IS-GPS-800A - US Coast Guard Navigation Center

Figure 3.2-5. Parity Check Matrix H for LDPC CodeTables 6.2-2, 6.2-3, 6.2-4, 6.2-5, 6.2-6, and 6.2-7 shall define the coordinates of elements with value “1” in each of thesubmatrices A, B, C, D, E, and T, respectively, for Subframe 2. Tables 6.2-8, 6.2-9, 6.2-10, 6.2-11, 6.2-12, and 6.2-13shall define the coordinates of elements with value “1” in each of the submatrices A, B, C, D, E, and T, respectively,for Subframe 3. The inverse of T is not included in this document, however T is a lower triangular matrix andtherefore, the inverse of T can be easily identified.The rate ½ LDPC encoder shall use the given matrices A, B, T, C, D, and E of Section 6.2.4 to generate the encodedsymbols using the following algorithm:where,andtp 1 = 1 (E T 1 A + C) s ttp 2 = 1 (A s t + B p t 1 ) = E T 1 B + D,s = subframe 2 or subframe 3 data,[ ] t indicates transpose,elements of matrices p 1 and p 2 are modulo 2 numbers.The encoded symbols for broadcast are comprised of (s;p 1 ;p 2 ) where s is the systematic portion of the codeword, and{p 1, p 2} comprise the combined parity bits.22 IS-GPS-800A8 June 2010