Indyk S. The formation methods of complex signal ensembles for cognitive telecommunication systems

The dissertation research is devoted to the development of the formation methods of complex signal ensembles for cognitive telecommunication systems, which allow increasing the volume of ensembles while providing a low level of multiple access interference. The analysis of ways to increase the volume of complex signal ensembles for cognitive telecommunication systems (CTS), was performed. It is revealed that the intercorrelation properties of the signals of one system are the main factor influencing the value of the multiple access interference (MAI) in the CTS. Known methods of struggle with MAI do not reduce their level to an acceptable value in case of accidental temporary shift. It is proved that the use of ensembles of complex signals based on sequences with improved intercorrelation properties is optimal. The purpose of the dissertation is to develop methods for forming ensembles of complex signals for CTS, which allow to increase the volume of ensembles while ensuring a low level of MAI. For the first time, a method of permutation of frequency elements of signals by complete search was developed, which allows increasing the volume of complex signals ensembles by m times. The essence of the method is to compare the values of the maximum emissions of the side lobes of the cross-correlation function (CСF) of signals, formed by frequency filtering of different output sequences in different frequency bands. If in the process of calculations, a signal is detected, the interaction with which violates the compliance of the condition of minimum similarity, it is excluded from the array of values. Permutation occurs by complete search. Improved method of forming of complex signals ensembles obtained by permutation of time intervals of sequences based on a centered series, which differs from the known in formation of a centered series based on the average value of maximum emissions of side lobes of CCF, which reduces the level of multiple access interference and increase the ensemble volume. The signals generated by this method have a low level of MAI, which is determined by the values of the maximum emissions of the side lobes of the CCF. The formation method of complex signals ensembles, based on sequences with improved intercorrelation properties, which are obtained by bandpass filtering with permutations, implemented on the basis of selection from the spectrum of sequences of equal bands with subsequent transfer in the common frequency domain and the subsequent application of permutations, which allows you to form ensembles of complex signals with the required levels of maximum emissions of the side lobes of CCF. The comparative characteristic of intercorrelation properties of signals is studied, as a result of which it is revealed that the formed signal ensembles, by the method of permutation of time intervals of sequences on the basis of the centered series, have better intercorrelation properties than ensembles on the basis of known signals. The level of maximum emissions of the side lobes of the CCF of the developed signals is 7-12 % less than the known signals. The comparative characteristic of ensemble properties of signals, on the basis of sequences with the improved intercorrelation properties which are received by a bandpass filtering with permutations with known signals is studied. The obtained results show that the formed ensembles of signals have a larger volume (by 16-26 %) in comparison with ensembles based on known signals. Developed signals should be used with any number of subscribers. The filter band should be selected in the range from 0.1 to 2 % of the total width of the main lobe of the sequence spectrum for practical use in cognitive telecommunications systems.