Publication: Magyar Közlöny
Issue: MK-2009-104 (Year: 2009, Number: 104)
Era: 2004-2010
Section: 
Paragraph Index: 2147

b) Long UAT ADS-B message: Parity shall be a RS (48, 34) code. Note.— This results in 14 bytes (code symbols) of parity capable of correcting up to 7 symbol errors per block. For either message length the primitive polynomial of the code shall be as follows: p(x) = x8 + x7 + x2 + x + 1 The generator polynomial shall be as follows: ) ( ∏ = − P i i x α where: P = 131 for RS (30, 18) code, P = 133 for RS (48, 34) code, and α is a primitive element of a Galois field of size 256 (i.e. GF(256)). Annex 10 — Aeronautical Communications Volume III 22/11/07 I-12-10 12.4.4.1.3.2 Transmission order of FEC parity FEC parity bytes shall be ordered most significant to least significant in terms of the polynomial coefficients they represent. The ordering of bits within each byte shall be most significant to least significant. FEC parity bytes shall follow the message data block. 12.4.4.2 UAT GROUND UPLINK MESSAGE The Active portion of a UAT ground uplink message shall contain the following elements, in the following order: — Bit synchronization — Interleaved message data block and FEC parity. 12.4.4.2.1 BIT SYNCHRONIZATION The first element of the Active portion of the UAT ground uplink message shall be a 36-bit synchronization sequence. For the UAT ground uplink message the sequence shall be: 000101010011001000100101101100011101 with the left-most bit transmitted first. 12.4.4.2.2 INTERLEAVED MESSAGE DATA BLOCK AND FEC PARITY 12.4.4.2.2.1 Message data block (before interleaving and after de-interleaving) The UAT ground uplink message shall have 3 456 bits of message data block. These bits are divided into 6 groups of 576 bits. FEC is applied to each group as described in 12.4.4.2.2.2. Note.— Further details on the format, encoding and transmission order of the UAT ground uplink message data block are provided in Section 2.2 of Part I of the Manual on the Universal Access Transceiver (UAT) (Doc 9861). 12.4.4.2.2.2 FEC parity (before interleaving and after de-interleaving) 12.4.4.2.2.2.1 Code type The FEC parity generation shall be based on a systematic RS 256-ary code with 8-bit code word symbols. FEC parity generation for each of the six blocks shall be a RS (92,72) code. Notes.—

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