A frame contains m data bits (messages) and r redundant bits (parity bits). The total length of a frame = data bits+redundant bits, and the x-th bit unit containing data bits and parity bits usually becomes an x-bit codeword. A code word is composed of several symbols, and the communication in computer communication is represented by several binary codes.
Extended data
The application principle of code:
In practical application, in addition to eliminating error diffusion at regular intervals and solving rate matching by buffer storage, it mainly solves the statistical matching of small symbol sets, such as the statistical matching of black (1) and white (0) fax sources, and forms an extended symbol set source by using different runlengths of 0 and 1. Runlength refers to the length of the same symbol (such as the length or number of a continuous string of 0 or a string of 1 in binary code).
According to CCITT standard, 2× 1728 runs (length) need to be counted, and the storage capacity is too large. In fact, the probability of long run is very small, so CCITT also stipulates that if L represents the run length, L = 64q+R. Where Q is the main code and R is the base code. When encoding, the run length of not less than 64 consists of the main code and the base code. When l is an integer multiple of 64, only codes with main codes and codes without base codes are used.