XI Международная студенческая научная конференция Студенческий научный форум - 2019

Ensuring high reliability of data transmission over radio communication channels is considered one of the problems of modern radio engineering. Multipath propagation, various interference, signal attenuation and many other causes lead to errors. There are a large number of ways to improve the reliability of the transmitted data through the communication channel: increasing the antenna gain, increasing the sensitivity of the receiver, increasing the power of the transmitter, the use of diversity reception etc.

Previously listed methods of improving the reliability of the transmitted data are difficult to apply or economically unprofitable. Another method of improving the reliability of information transmission is the method of error-correcting coding. The theory of error-correcting coding is based on the results of research done by Claude Shannon. He formulated a theorem for a discrete channel with noise: if the transmission rate of binary characters is less than the bandwidth of the channel then there is a code in which the probability of error in decoding is small.

Available error-tolerant codes are usually focused on packet modes of communication systems. In practice there are a relatively small group of algebraic error-correcting codes: reed-Solomon codes, Bose-Chowdhury-Hoquinghem, turbo codes, convolutional codes.

Codes Bose — Chowdhury — Hoquinghem is a broad class of cyclic codes used to protect data from errors. They differ in the possibility of building code with predefined correcting qualities, namely, the smallest distance of the code.

The turbo code is a parallel cascade of a systematic block code that can correct errors that occur during transmission of digital information via communication channels with noise.

The main drawback is the relatively high decoding complexity and high latency, which leads to inconveniences for some applications.

The procedure of coding with convolutional code leads to the calculation of convolution of a constant information flow of symbols with established sequences of length K(code restriction).

With the Reed-Solomon code, it is possible to read a CD with a lot of scratches or transmit data under conditions of high interference. Typically, for a CD, code redundancy (that is, the number of additional characters that can be recovered) is approximately 25%. In this case, you can restore the amount of data equal to half of the excess. If the disk capacity is 700 MB, in this case, it turns out, at the theoretical level, it is possible to restore up to 87.5 MB from 700. In this regard, we do not need to know which of the characters is transmitted with an error. In addition, it should be noted that in conjunction with the encoding, an alternation is used when the bytes of different blocks are mixed in a specific order, which as a result makes it possible to read disks with extensive damage localized close to each other (for example, deep scratches), so after the operation, reverse alternation, extensive damage turns into single errors in a large number of code blocks that can be restored.

Reed-Solomon codes are considered to be cyclic, so they are most easily implemented in practice. They have the greatest code distance in comparison with other codes, so this type of code is widely used in telecommunication systems.

Since Reed-Solomon codes are relatively easy to implement in practice they are the cheapest that explains the choice of this code.

Literature:

1. Sclar B, Digital communication. Theoretical fundamentals and practical application –M.: Publishing house “Williams”, 2003

2. Prokis, Journal Digital communication. –Moscow: Radio and communication, 2000

3. Feer, K. Wireless digital communication. Modulation techniques and spread spectrum –Moscow: Radio and communication, 2000: