tailieunhanh - Lecture Digital communication systems - Lecture 6

In this chapter we will discuss: Magazine history, magazines in the digital age, defining features of magazines, organization of the magazine industry, magazine ownership, producing the magazine, economics, feedback, the magazine industry. | A í - INTRODUCTION TO EECS II DIGITAL COMMUNICATION SUSTEMS Fall 2012 Lecture 6 Convolutional codes State-machine view trellis Fall 2012 Lecture 6 Slide 1 Error Control Codes for Interplanetary Space Probes Early Mariner probes 1962-1967 Mars Venus -no ECC Later Mariner and Viking probes 1969-1976 Mars Venus - linear block codes . 32 6 16 bi-orthogonal or Hadamard code codewords comprise the all-0 word the all-1 word and the other codewords all have sixteen 0 s sixteen 1 s. The complement of each codeword is a codeword. Fall 2012 Lecture 6 Slide 2 Bi-orthogonal Codes . used on Mariner 9 1971 Mars orbit to correct picture transmission errors. Data word length k 6 bits for 64 grayscale values. Usable block length n around 30 bits. Could have done 5-repetition code but comparable rate with better error correction from a 32 6 16 Hadamard code. Used through the 1980 s. The efficient decoding algorithm was an important factor in the decision to use this code. The circuitry used was called the Green Machine . More generally for such codes n 2A k-1 d 2A k-2 Fall 2012 Lecture 6 Slide