130x1g2 - CCSDS

TM SYNCHRONIZATION AND CHANNEL CODING—SUMMARY OF CONCEPT AND RATIONALEModulating Waveform: A way of representing data bits (‘1’ and ‘0’) by a particularwaveform.NRZ-L: A data format representations in which a data ‘one’ is represented by one of twolevels, and a data ‘zero’ is represented by the other level.NRZ-M: A data format representations in which a data ‘one’ is represented by a change inlevel and a data ‘zero’ is represented by no change in level.Octet: An 8-bit word consisting of eight contiguous bits.Outer Code: In a concatenated coding system, the first encoding algorithm that is applied tothe data stream.Packet: An efficient application-oriented protocol data unit that facilitates the transfer ofsource data to users.Protocol: A set of procedures and their enabling format conventions that define the orderlyexchange of information between entities within a given layer of the TM System.Reed-Solomon (RS) Symbol: A set of J bits that represents an element in the Galois fieldGF(2 J ), the code alphabet of a J-bit Reed-Solomon code.Reliable: Meets the quality, quantity, continuity and completeness criteria which arespecified by the TM System.Segment: A protocol data unit which facilitates telemetry flow control through the breakingof long source packets into communications-oriented data structures.Systematic Code: A code in which the input information sequence appears in unaltered formas part of the output codeword.Telemetry System: The end-to-end system of layered data handling services which exist toenable a spacecraft to send measurement information, in an error-controlled environment, toreceiving elements (application processes) in space or on Earth.Transfer Frame: A communication oriented protocol data unit that facilitates the transfer ofapplication oriented protocol data units through the space-to-ground link.Transparent Code: A code that has the property that complementing the input of the encoderor decoder results in complementing the output.User: A human or machine-intelligent process which directs and analyzes the progress of aspace mission.Virtual Channel: A given sequence of Transfer Frames, which are assigned a commonidentification code (in the Transfer Frame header), enabling all Transfer Frames who aremembers of that sequence to be uniquely identified. It allows a technique for multiple sourceCCSDS 130.1-G-2 Page A-2 November 2012