Key Technologies Of Protocol Identification For Ccsds Data Link Layer

The CCSDS protocol identification technologies play a important role in space information acquisiton and analysis. Its application area covers research on standardization of space protocol in cooperation mission and space information countermeasure. The former focus on normalization of protocol used by terminals via analyzing types and formats of protocol data unit, while the later is interested in extracting useful information and gaining control of the battle field.Data link layer is right above physical layer and it is the key component to acquire space information. Because of this, we carry out the research on key technogy of CCSDS protocol recognition which is involved in three data link sublayers: Telecommand(TC), Telemetry(TM) and Advanced orbiting system(AOS). The main contents and creative results are outlined as following.Firstly, the basic layout of CCSDS data link protocol was analyzed and transfer frame formats of TC,TM and AOS were described. The frame synchronization methods and coding patterns in synchronization and coding sublayer were sumed up and the key technologies involved in CCSDS data link protocol recognition were put up with. A resolution used in protocol identification is pattern-matching method. Several classical pattern-matching algorithms, such as BF,BM,BMH and QS were analyzed. Based on an alalysis of pattern string in CCSDS data link layer and QS algorithm, a revised version of pattern-matching algorithm was presented and higher string-searching speed is then possible.With regard to channel coding recognition in CCSDS, the linear block code was analyzed and identification methods based on Gaussian Elimination and syndrome check was given for CCSDS BCH code. Three recognition algorithms of rate-1/2 convolutional code were employed to demonstrate their performance in CCSDS convolutional code's identification. The punctured version of (2,1,6)-convolutional code was also studied as well as its identification method based on shortened vecter of check matrice. To RS code's recognition, transfer frame length is used to roughly judge the interleaving depth of RS (255,223) or RS(255,239) , then the Galois Field Fourier Transform (GFFT) is introduced to verify the identification results. Identification methods of pseudo-random code was discussed and a dominant value-finding method based on combinatorial enumeration was studied. Simulation results give a recognition threshhold 70% with 1's proportion in original binary series.Finally, the intact identification of CCSDS data link protocol was clarified through a designed simulation example. The time consumed in the process was given and the identification algorithms developed in this study were proved to be feasible and effective with simulation validation.