Intensive development of modern wirelesscommunications such as the systems of wireless access toInternet and local network systems operating in indoorenvironment provoked interest in study the features andmodels of wireless communication channels. The presence ofthe walls; partitions; furniture; radio electronic equipment;people and other objects inside the building create intricateenvironment for the propagation of radio waves. The maineffects observed in the propagation of radio waves inside thepremises are multipath due to multiple reflections of radiowaves from walls and other objects; diffraction on thenumerous sharp edges of objects located inside the room; andscattering of radio waves. These effects create intricateinterference structure of the electromagnetic field; whichvaries greatly when people and other objects move.UWB communication systems are characterized by highdata rates; low cost; multipath immunity; and large toleranceto interfering legacy systems. In recent years; UWBtechnologies have been rapidly developingPerformance of all known communication systems usingenergy-based receivers largely depends on the transmittedsignal energy; i.e. decision making is carried out at thematched filter output by estimation of signal energy. Due tothis principal peculiarity; deep fading attenuating of receivedsignal magnitude provokes considerable decreasing of signalenergy and; as consequence; performance provided bycommon energy-based decision making strategy is worsen.Suggested strategy exploiting for building novel UWBcommunication systems is based on the features of higher-order spectra. Performance provided by exploitingsuggested bispectrum-organized triplet-signals andbispectrum-based decision making for detection anddiscrimination the triplets depends on given phase couplingrelationships contained in triplet-signals. Because of this;despite considerable attenuating of triplet-signal amplitude;phase coupling information remains to be preserved for truetriplet-signals discrimination and correct decision making fordata passed through the fading wireless channel

One of the main problems in modern wireless telecommunication systems and networks is the transmission and reception of signals in a multipath environment. Due to the nonideal impulse response of the communication channel, the frequency selective fading of the transmitted signal occurs. Diffraction and interference effects create a complex non-stationary structure of the electromagnetic field, which varies greatly in space and time. The method of branched BIS is organized - redundant coding, which allows you to receive and recognize a signal in a digital communication system in the presence of additive Gaussian noise, multipath propagation of radio waves, fading, random signal delays, as well as random changes in Doppler frequency shift. The advantages of the bispectral signal processing method include the ability to identify and evaluate the phase relationships of the spectral components in the observation, high noise immunity with respect to additive Gaussian noise and invariance to random signal time delays. The proposed method is based on solving the problem of multi-alternative detection and distinguishing of known triple signals against the background of interference according to test statistics – estimating the amplitude bispectrum by comparing the corresponding peak values of bi-amplitudes at the output of the matched bispectral filter. Since the bi-amplitude serves as a measure of the contribution of the frequency-phase dependences specified in a polyharmonic signal, the reception rule is to choose a triplet as the solution of a bispectrically organized signal, whose frequency dependencies are most similar to the frequency dependencies in the adopted oscillation. The aim of the work is to substantiate the advantages of using a branched bispectrically-organized code in digital radio communication systems in conditions of fading and multipath propagation of radio waves in comparison with the known redundant code. The results of computer statistical modeling of communication systems with the proposed coding method and the known one show a lower probability of symbol error for branched bispectrically-organized redundant coding under conditions of multipath radio propagation channels within the considered Rice and Rayleigh fade models. Computer simulations performed to show that the proposed method of branched bispectrically-organized redundant coding improves noise immunity in the propagation of radio waves in a channel with additive white Gaussian noise and also in a multipath radio link with fast and slow fading compared to the known frequency-redundant system-prototype.