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Features Synchronization in Multipath Channels Digital Communiction Systems with Orthogonal Multi-Position Signals


G.N. Nurutdinov, V.G. Nurutdinov

The main problems encountered in the development of modern mobile communication systems (STIs) can be summarized as follows: 1) the ability to capture the signal, 2) the possibility of multiple access, and 3) the ACT sobnosti distinguish the desired signal from interference due to multipath signal (antimnogoluchevaya ability), and 4) suppression of narrow band-pass interference. If you do not use spread-spectrum signals and pseudo-randomly time-varying parameters (operating frequency, the code point of emission) or a special formation processing of signals (or both simultaneously), then due to fading and intersymbol interference can not provide reliable communications in multipath channel. Obligatory condition of performance of STI is to provide in its timing between the formation of the desired signal at the transmitting side and the formation of a reference signal at the receiver. Synchronization is divided into the system and the signal [3. System clock provides compensation for the mismatch of time scales hours sending and receiving reporters. Signal synchronization allows for a mismatch between the time of transmission and the time of admission to the input of the demodulator, resulting from a temporary delay in the propagation of the signal τ (t). Signal synchronization reduces to obtaining estimates of signal delay and includes the input mode to mode-matching and accurate tracking her. The peculiarity of the synthesis algorithms for pseudo-timing adjustment of the working frequency is that the concept phase of the signal in the traditional sense, is applicable only in the interval of constancy of the operating frequency. Because of the presence of random delays in receiving the signal, the value of the current phase is not preserved for the next interval. Even with the continued delay in the initial phases of the value of adjacent signal elements may differ materially due to jumps frequency. In this case, carry out monitoring of the current phase, based on the standard patterns of FAP, it is not possible. Purpose  to review the device time synchronization of STI with a pseudorandom operating frequency adjustment, located on board aircraft (LA). Outline possible ways of modernizing the system timing, adapted to the conditions of multipath. The output. In order to maintain simplicity of the device timings to give up the optimal scheme, and to use the scheme, obtained without taking into account the delayed signal. To reduce the effect of the delayed signal to the precision characteristics of the device timing is appropriate to introduce additional (coloring) manipulation of the law, known at the receiver. At the entrance to the demodulator further manipulation is removed. The structure of the delayed signal from the phase shift between the delayed signal, and further manipulating the sequence will be destroyed. In principle, additional manipulation of the signal should not expand the width of the spectral density of the signal. The accuracy characteristics of the device after the update timing signal can be estimated by counting the power of the delayed signal to the intensity of the additive white Gaussian noise.

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