International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

The article is a continuation of previous studies and deals with the results of research on the protection of multichannel data transmission systems with channel division by the signal code from unauthorized access. It is proposed to use derivatives of Walsh functions (with different generating functions) as spreading codes for the formation of noise-like signals in multichannel communication systems. The analysis showed that the correlation properties of the derivatives of Walsh functions used as spreading codes have significantly better correlation characteristics than the original ones. An analysis of various types of Walsh functions used as spreading codes for signals transmitted in multi-channel systems was carried out. As a result, there were defined the types of pseudo-random sequences for Walsh generating functions, in which
multiple access interference is absent. It was justified the advantage of using these signals in the development of CDMA systems in order to protect against interference from multiple and unauthorized access.

The article, been a continuation of previous studies, proposes and analyzes one of the ways to increase the efficiency of multichannel communication systems through the simultaneous use of several derivative systems of Walsh functions with different generating functions, which are necessary for constructing pseudo-random sequences (PSR). These sequences, in turn, are used as spreading codes when generating noise-like signals in multi-channel data transmission systems with channel separation (SDMA) according to the signal shape or code. The correlation properties of the PSR are studied and it is shown that, in the contrast of the known ones, the proposed approach makes it possible to increase the number of channels in the system without increasing the channel bandwidth that improves the efficiency of a multi-channel communication system.

In multichannel data transmission systems noise-like signals, generated on the basis of derivatives of the Walsh function are used. The article examines the correlation properties of derivatives of Walsh functions with generating functions in the form of perfect binary lattices, which make it possible to provide the necessary data synchronization when receiving signals. Also, it was justified the advantage of using these signals in the development of CDMA systems in order to reduce the interference level of multiple access and to protect against unauthorized access.

The article presents the results of researches that are a continuation of analyzes of the correlation properties of generating functions intended for the formation of derivatives of Walsh functions. The derivatives of the Walsh functions are designed to obtain pseudorandom sequences (PRS) used in the formation of noise-like signals in multichannel data transmission systems with channel division according to the shape (code) of the signal. The analysis performed showed that the correlation properties of the derivatives of the Walsh functions depend on the type of generating functions, which were the modified Barker codes – direct and inverse composite Barker codes and de Bruijn sequences. It was justified the advantage of using these signals in the development of CDMA systems in order to reduce the interference level of multiple access and to protect against unauthorized access.

The article presents a continuation of researches in the field of improvement of signal quality in data transmission systems with code division multiple access (CDMA). It is discussed the correlation properties of pseudo-random sequences (PRS) used in the formation of noise-like signals in CDMA systems. The analysis, carried out in MATLAB environment, showed that correlation properties of the Walsh functions derivatives, used for generating PRS, have much better correlation characteristics than the original Walsh functions. Besides, these properties depend on the type of generating function of Walsh functions derivatives. It was justified the advantage of using these signals in the development of CDMA systems in order to improve the signal quality.