We need a simple example (in the form of a code or not - anyway) describing the work of linear block coding with parity.
I did not find a normal source on the Internet (which is in the Russian-speaking, that on the English-speaking sides). Either these are notes / books / etc. filled with matane so that the eyes converge in a handful, or these are examples of the implementation of the Hamming code, both in the variation “on the fingers” and in the variants of the finished code.
The most interesting thing is that I already understand Hamming more or less, but the catch is in contrast to ordinary block coding.
All this is necessary in order for me to explain in my own words the difference between the methods (their implementation in the code) on the exam.
If someone helps a link or some source - I will be grateful.
1 answer
I will quote from here :
When transmitting digital information, the quality of transmission is often evaluated by the number of distorted bits out of the total number received. And since it is impossible to obtain an ideal radio channel, we must allow a certain number of distorted bits and be ready to recover information or, as a last resort, determine that the presence of errors does not allow using the received information. To ensure the required characteristics in the radio channel with fading, linear (channel) coding is used, which implies some redundancy. Encoding, which allows to recognize and correct errors, can be divided into two categories: block coding and error correction. Block coding provides for the addition of check bits to the block of information, by the value of which at the receiving end it is possible to determine whether the received information is reliable. Error correction codes (correction codes) allow to correct errors introduced by a radio channel. GSM uses both block coding and error correction coding. And in this case, when receiving information at the beginning, error correction is carried out with the help of a correction code, if possible, and then using the block coding check bits, a check is made: whether the received information can be used. The coding of information in GSM is presented in Fig.2.2. In order of importance code combination in
260 bits are divided into three blocks: 50 bits, 132 bits, 78 bits. Three check bits are added to a block of 50 bits, and four check bits are added to a block of 132 bits. Next, the first two blocks, together with the check bits, are encoded with codes that allow to correct errors, and as a result we get 378 bits. Thus, we have 378 bits of encoded and 78 bits of uncoded information, which form a code pattern of 456 bits. This code combination characterizes a speech segment of 20 ms and must be transmitted over the air. In this case, the required data transfer rate is already 22.8 kbit / s.
It is also worth reading, if not all, then starting with page 225 of E. Tanenbaum’s book “Computer Networks” (5th edition)
