ccsds 131.0-b-2

CCSDS RECOMMENDED STANDARD FOR TM SYNCHRONIZATION AND CHANNEL CODING10 TRANSFER FRAME LENGTHS10.1 OVERVIEWNeither the TM Space Data Link Protocol (reference [1]) nor the AOS Space Data LinkProtocol (reference [2]) specifies the length of Transfer Frames because there are constraintson the Transfer Frame length depending on the selected coding options.The constraints on Transfer Frame lengths specified in this section apply to both TMTransfer Frames and the AOS Transfer Frames.10.2 GENERAL10.2.1 Once selected, the Transfer Frame length shall be fixed for a Mission Phase on aparticular Physical Channel.NOTE – The Transfer Frame lengths shown here do not include the length of the AttachedSync Marker (ASM) specified in section 8.10.3 CASE 1: UNCODEDThe length of the Transfer Frames shall be any integer number of octets, as required by theusing project, with a maximum of 2048 octets.10.4 CASE 2: CONVOLUTIONAL ONLYThe length of the Transfer Frames shall be any integer number of octets, as required by theusing project, with a maximum of 2048 octets.10.5 CASE 3: REED-SOLOMON ONLYNOTES1 With the Reed-Solomon Codes specified in section 4, only certain specific lengths ofTransfer Frames may be contained within the codeblock’s data space. In some casesthese lengths can be shortened at a small sacrifice in coding gain.2 Since these R-S codes have a symbol length of 8 bits, the length of the codeblock (inoctets) is a multiple of the interleaving depth, which provides ‘octet compatibility’.10.5.1 If necessary, Transfer Frame lengths shall be shortened in discrete steps by usingvirtual fill.CCSDS 131.0-B-2 Page 10-1 August 2011