Synchronization Mode Transitions Induced by Chaos in Modified Morris-Lecar Neural Systems with Weak Coupling

Based on a modified Morris–Lecar neural model, the synchronization modes transitions between two coupled neurons or star-coupled neural network connected by weak electrical and chemical coupling are respectively investigated. For the two coupled neurons, by increasing the calcium conductivity, it is found that the period-2 synchronization of action potential of neurons is transformed to desynchronization first, and then to period-3 synchronization. By increasing the potassium conductivity, however, the synchronization mode transition is a reversal direction process as mentioned above. The bifurcation analysis of inter-spike interval shows that the synchronization modes transition is induced by the chaos. The stronger the coupling strength is, the smaller the period-2 synchronization region in the parameters plane is, while the larger the period-3 synchronization region will be. For the star-coupled neural network, in the presence of weak electrical coupling, it can exhibit the complete synchronization, desynchronization, and drum head mode states under different parameter values, respectively. In the presence of chemical synapse, however, the completely synchronized state can not be observed in the star-coupled neural network. Our results might provide novel insights into synchronization modes transition and related biological experiments.

SYNCHRONIZATION IN TIME-DUPLEX RADIO SYSTEMS

Рассмотрена работа в режиме синхронизации системы связи стандарта МАКВИЛ, использующей организацию радиосвязи с временным дуплексом. Получен базовый вариант оптимального алгоритма обработки одиночных замеров син -хронизации, ориентированный на работу в канале с белым гауссовским шумом при неизвестных, но стабильных спектральных искажениях сигнала. На основе разработанного алгоритма предложено множество вариантов статистического накопления измерений для режима синхронизации в нестационарных условиях. На моделях многолучевого распространения, утвержденных международными рекомендациями, выявлены наилучшие варианты алгоритмов синхронизации с накоплением. Operation in synchronization mode of the McWiLL standard communication system, using the organization of radio communication with time duplex, is considered. A basic version of the optimal algorithm for processing single synchronization measurements is obtained, which is focused on working in a channel with white Gaussian noise at unknown but stable spectral distortions of the signal. Based on the developed algorithm, many variants of statistical accumulation of measurements for the synchronization mode in non-stationary conditions are proposed. Using multipath propagation models approved by international recommendations, the best variants of synchronization algorithms with accumulation are identified.

Light-powered Self-excited Coupled Oscillators in Huygens ’ Synchrony

Self-excited motions have the advantages of actively collecting energy from the environment, autonomy, making equipment portable and so on, and a great number of self-excited motion modes have recently been developed which greatly expand the application in active machines. However, there are few studies on the synchronization and group behaviors of self-excited coupled oscillators, which are common in nature. Based on light-powered self-excited oscillator composed of liquid crystal elastomer (LCE) bars, the synchronization of two self-excited coupled oscillators is theoretically studied. Numerical calculations show that self-excited oscillations of the system have two synchronization modes: in-phase mode and anti-phase mode. The time histories of various quantities are calculated to elucidate the mechanism of self-excited oscillation and synchronization. Furthermore, the effects of initial conditions and interaction on the two synchronization modes of the self-excited oscillation are investigated extensively. For strong interactions, the system always develops into in-phase synchronization mode, while for weak interaction, the system will evolve into anti-phase synchronization mode. Meanwhile, the initial condition generally does not affect the synchronization mode and its amplitude. This work will deepen people's understanding of synchronization behaviors of self-excited coupled oscillators, and provide promising applications in energy harvesting, signal monitoring, soft robotics and medical equipment.

Noise Properties of Two Mutually Coupled Spin-Transfer Nanooscillators in the Phase Locking Regime

Introduction. Today, many research endeavors are devoted to the miniaturization of microwave sources. One of the promising approaches is the use of magnetic nanostructures (spintronics elements), providing a wide range of frequency tuning and low power consumption. The main disadvantage of spintronics generators (spintransfer nanoscillators ‒ STNO) is a low output power of generated oscillations (tens of nanowatts and less). A possible solution is to sum up the power of many STNOs in a mutual synchronization mode.Aim. The investigation of noise properties of two connected STNOs with identical and non-identical parameters in a phase synchronization mode.Materials and methods. A model was developed of two STNOs interconnected by spin waves taking into account thermal noises. Spectral power densities of the amplitude and phase noise were obtained by the method of effective linearization.Results. Dependencies were obtained in a general form for attenuation coefficients of the amplitude and phase fluctuations of noise sources for each STNO. Three cases of synchronization were considered: completely identical STNOs, two identical STNOs but with different oscillation frequencies, and two non-identical STNOs, differing in an allowance of self-excitation by frequencies and amplitudes of the oscillations. It was possible to obtain a gain in the amplitude and phase noise for two identical STNOs. In this case, an increase in the allowance of self-excitation led to a decrease in the level of phase and amplitude noise.Conclusion. This analysis of the attenuation coefficients for non-identical STNOs demonstrates the possibility of improving the noise properties of each of the generators. In this case, the best noise value is obtained for an STNO with greater stability in a stand-alone mode.

Phase Synchronization Impact on Throughput Performance in LTE Network

This paper presents a study of phase synchronization impact on throughput in Long Term Evolution (LTE) network with different transport protocols. Phase synchronization is needed for advanced features in LTE and other precise technologies with minimal clock error of Nano seconds. An End to End LTE testing environment is built by using real User Equipment (UE) and LTE core network for studying the throughput impact due to Phase Synchronization in different transport modes. This experimentation is carried out for comparing the throughput of the system with Frequency Synchronization Mode (FM) and Frequency & Phase synchronization Mode (FPM). A novel study has been conducted on throughput for TCP and UDP traffic in different LTE bandwidths, based on real traffic conditions. The study shows that system performance in Uplink (UL) and Downlink (DL) throughput has improved by using Frequency along with Phase synchronization in LTE network using GPS as a clock source.