Effect Of Synchronization Error Research Articles

Effect of synchronization system errors on the reception noise immunity of amplitude-phase shift keyed signals

Objectives. An urgent task in the context of modern radio and television systems is to improve the quality and quantity of transmitted information. For example, the use of multiple amplitude-phase shift keyed (APSK) signals—16-APSK and 32-APSK—in digital satellite television systems of the Digital Video Broadcasting-Satellite2 (DVB-S2) standard made it possible to transmit 30% more data in the same frequency bands in comparison with the previous DVB-S standard. Such increases in information transmission rates impose more stringent requirements on hardware. An important role in the reception of APSK signals, as well as the signals of other coherent signal processing systems, is played by the stability of synchronization systems. The presence of operational errors can significantly reduce the quality of information reception. The aim of the present work was to analyze the effect of phase and clock synchronization errors on the reception noise immunity of APSK signals with a ring signal constellation structure.Methods. The study used statistical radio engineering methods informed by optimal signal reception theory.Results. The effect of phase and clock synchronization errors on the reception noise immunity of APSK signals having a signal constellation ring structure is analyzed. The dependencies of the bit error probability on the magnitude of the phase shift and the clock offset were characterized. The effect of synchronization errors on reception quality were compared with the known results for quadrature amplitude modulation (QAM) signals.Conclusions. At an acceptable energy loss of no more than 1 dB, the critical phase error can be considered as 2°-3°, while the critical clock error is 3-4%. A coherent receiver of APSK signals is more sensitive to the phase error of reference oscillations than a similar receiver of QAM signals, whereas clock errors have the same effect on the reception quality of these signals.

Development of an Algorithm for Clustering Cardiac ECG Signals with Post-Correction for Long-Term ECG Monitoring

Introduction. The most common method for diagnosing cardiovascular diseases is the method of ECG monitoring. In order to facilitate the analysis of the obtained monitorograms, special software solutions for automated ECG processing are required. One possible approach is the use of algorithms for automated ECG processing. Such algorithms perform clustering of cardiac signals by dividing the ECG into complexes of similar cardiac signals. The most representative complexes obtained by statistical averaging are subject to further analysis.Aim. Development of an algorithm for automated ECG processing, which performs clustering of cardiac signals by dividing the ECG into complexes of similar cardiac signals.Materials and methods. Experimental testing of the developed software was carried out using patient records provided by the Pavlov First State Medical University of St Petersburg. The software module was implemented in the MatLab environment.Results. An algorithm for clustering cardiac signals with post-correction for the tasks of long-term ECG monitoring and a software module on its basis were proposed.Conclusion. The presence of a small number of reference cardiac signal complexes, obtained through ECG processing using the proposed algorithm, allows physicians to optimize the process of ECG analysis. The as- obtained information serves as a basis for assessing dynamic changes in the shape and other parameters of cardiac signals for both a particular patient and groups of patients. The paper considers the effect of synchronization errors of clustered cardiac signals on the shape of the averaged cardiac complex. The classical solution to the deconvolution problem leads to significant errors in finding an estimate of the true form of a cardiac signal complex. On the basis of analytical calculations, expressions were obtained for the correction of clustered cardiac signals. Such correction was shown to reduce clusterization errors associated with desynchronization, which creates a basis for investigating the fine structure of ECG signals.

Stability of Tracking the Delay of Phase-shift Keyed Signals with Spectrum Expanding in Synchronization Systems of Radio Engineering Systems

The issues of ensuring the stability of delay tracking in synchronization systems of radio engineering systems when receiving phase-shift keyed signals with spectrum expansion based on pseudorandom sequences are considered. When working with moving objects, the delay of the received signal continuously changes, synchronization errors occur, and the quality of signal reception largely depends on the stability of the tracking scheme for the delay, characterized by the probability of tracking failure. Delay tracking is usually considered as the main task of the synchronization system of the considered radio systems with phase-manipulated signals with spectrum expansion based on pseudo-random sequences.
 The effect of synchronization errors when tracking the delay of a received phase-shift keyed signal with a spectrum extension based on pseudorandom sequences on the probability of tracking failure is studied. The calculation method is used to obtain families of dependences of the probability of tracking failure on the values of random and systematic components of the delay tracking error, normalized to the capture band of the time discriminator of the delay tracking scheme for various combinations of these parameters. The areas of weak and strong influence of the value of tracking errors over the delay of the received signal on the probability of tracking failure are determined. The nature of impact of random and systematic components of tracking error on the probability of failure of tracking was analyzed and it was found that in the General case is the ambiguity of normalized mean square of tracking error as the optimization criterion while minimizing the likelihood of tracking loss.
 Calculations performed for a wide range of changes in the normalized delay tracking errors show that to ensure a given quality of signal reception in a radio system with phase-shift keyed signals with spectrum expansion based on pseudorandom sequences, a joint choice of parameters of the delay tracking system that determine the value of random and systematic components of the tracking error is necessary. The results obtained can be used to analyze the characteristics of synchronization systems that monitor the parameters of received signals with a spectrum extension, and to justify the technical solutions of the synchronization system that provide the required quality of signal reception in information and measurement of radio-electronic systems.

FD Multi-User Mobile System With Timing Errors

The error performance is analyzed for a full-duplex (FD) multi-user amplify-and-forward two-way relay system with users’ mobility. The residual self-interference (RSI) at FD users is modeled as a Rician distributed random variable. The closed-form expression for the symbol error probability with various modulation schemes is derived for hybrid scheduling scheme assuming independent and non-identically distributed Rayleigh fading channels. The effect of synchronization error is also investigated in case of binary phase shift keying. The numerical results are shown for the irreducible error floor, comparison of half-duplex and FD system and for the effects of RSI on the system performance.

The effect of non-synchronous sensing on structural identification and its correction

The goal of this study is to investigate the effect of non-synchronous sensing when using wireless sensors on structural identification and to attempt correcting such errors in order to obtain a better identification result. The sources causing non-synchronous sensing are discussed first and the magnitudes of such synchronization errors are estimated based on time stamps of data samples collected from Imote2 sensors; next the impact of synchronization errors on power spectral densities (PSDs) and correlation functions of output responses are derived analytically; finally a new method is proposed to correct such errors. In this correction method, the corrected PSDs of output responses are estimated using non-synchronous samples based on a modified FFT. The effect of synchronization errors in the measured output responses on structural identification and the application of this correction method are demonstrated using simulation examples. The simulation results show that even small synchronization errors in the output responses can distort the identified modal and stiffness parameters remarkably while the parameters identified using the proposed correction method can achieve high accuracy.

분산 빔포밍을 이용한 OFDM 시스템에서의 동기에러 영향 분석

분산 빔포밍을 이용한 OFDM 시스템에서의 동기에러 영향 분석

Research on Simulation of Giant Forging Hydraulic Press Decoupling Control for Synchronous Control System

A giant forging hydraulic press active synchronous control system is a mutually-coupled multi-input and multi-output system. To solve the elimination of the multi-channel interference, a multiple-input and multiple-output mathematical model center on active-beam is established; multi-channel synchronous decoupling control strategy is studied. The simulation results show that: the system eliminates the role of strong interference between multi- channel accesses to very good inhibitory effect of synchronization error, eliminating the system's external disturbance on the synchronization precision control impact.

Quasi-Synchronous Cooperative Networks: A Practical Cooperative Transmission Protocol

In this article, we propose a cooperative space-time coding (STC) protocol, amalgamating the concepts of asynchronous cooperation, noncoherent detection, as well as distributed turbo coding (DTC), where neither symbol-level time synchronization nor channel-state information (CSI) estimation is required at any of the cooperating nodes, while attaining high performance even at low signal-to-noise ratios (SNRs). More specifically assuming the system configuration of a single source node, multiple relay nodes, and a single destination node, each having a single antenna element (AE)a practical cooperative differential space-time spreading (CDSTS) scheme is designed using interference rejection spreading codes, to eliminate the effect of synchronization errors between the relay nodes without the assistance of channel estimation or equalization.

Time Synchronization for Cooperative Communication in Wireless Sensor Networks

Time synchronization is crucial for the implementation of cooperative communication in wireless sensor networks. In this paper, we explore the effect of synchronization error on cooperative communication utilizing distributed Alamouti code. The analysis and simulation results show that small synchronization error has negligible effect on bit error rate (BER) performance. In order to synchronize the distributed sensor nodes within an acceptable error, we propose a physical layer synchronization scheme. This scheme consists of an initial synchronization of the cooperative transmitters, synchronization error estimation at the cooperative receiver and finally a feedback phase. A maximum likelihood method is proposed to make the synchronization error estimation. It achieves better performance than the matched filter method at the price of moderate increase in computational complexity and memory space. Two strategies after synchronization error estimation have been analyzed. They provide better BER performance in the existence of initial synchronization error. They are practical to be implemented in the sensor nodes before the Alamouti decoding.

Sleep/wake scheduling for multi-hop sensor networks: Non-convexity and approximation algorithm

We investigate the problem of sleep/wake scheduling for low duty cycle sensor networks. Our work differs from prior work in that we explicitly consider the effect of synchronization error in the design of the sleep/wake scheduling algorithm. In our previous work, we studied sleep/wake scheduling for single hop communication, e.g., intra-cluster communication between a cluster head and cluster members. We showed that there is an inherent trade-off between energy consumption and message delivery performance (defined as the message capture probability). We proposed an optimal sleep/wake scheduling algorithm, which satisfies a given message capture probability threshold with minimum energy consumption. In this work, we consider multi-hop communication. We remove the previous assumption that the capture probability threshold is already given, and study how to decide the per-hop capture probability thresholds to meet the Quality of Services (QoS) requirements of the application. In many sensor network applications, the QoS is decided by the amount of data delivered to the base station(s), i.e., the multi-hop delivery performance. We formulate an optimization problem to set the capture probability threshold at each hop such that the network lifetime is maximized, while the multi-hop delivery performance is guaranteed. The problem turns out to be non-convex and hence cannot be efficiently solved using standard methods. By investigating the unique structure of the problem and using approximation techniques, we obtain a solution that provably achieves at least 0.73 of the optimal performance. Our solution is extremely simple to implement.

Optimal Sleep/Wake Scheduling for Time-Synchronized Sensor Networks With QoS Guarantees

We study sleep/wake scheduling for low-duty cycle sensor networks. Our work explicitly considers the effect of synchronization error. We focus on a widely used synchronization scheme and show that its synchronization error is nonnegligible and using a conservative guard time is energy wasteful. We formulate an optimization problem that aims to set the capture probability threshold for messages from each individual node such that the expected energy consumption is minimized, and the collective quality of service (QoS) over the nodes is guaranteed. The problem is nonconvex. Nonetheless, we are able to obtain a solution with energy consumption that is provably at most 37% larger than the optimal solution. Simulations demonstrate the efficacy of our solution.

On Synchronization Errors in Networked Feedback Systems

This paper addresses the problem of synchronization errors and their effects on feedback loops that are closed over communication networks. It is assumed that the feedback loop consists of two discrete-time systems, the clock frequency ratio of which has a special rational form, and is close to one. A Toeplitz matrix approach is taken to model the input/output relationship of the arising feedback systems. Based on this representation, the effect of synchronization errors on stability of the feedback systems is analyzed. It is shown that stability of the synchronized feedback loop can not guarantee stability of the loop in the presence of synchronization errors. Necessary and sufficient stability conditions are derived

Effect of synchronization errors on the performance of multicarrier CDMA systems

A synchronous multicarrier (MC) code-division multiple access (CDMA) system using inverse fast Fourier transform (IFFT) and fast Fourier transform (FFT) for the downlink mobile communication system operating in a frequency selective Rayleigh fading channel is analyzed. Both carrier frequency offset and timing offset are considered in the analysis. Bit error rate performance of the system with both equal gain combining and maximum ratio combining are obtained. The performance is compared to that of the conventional system using correlation receiver. It is shown that when subcarrier number is large, the system using IFFT/FFT has nearly the same performance as the conventional one, while when the subcarrier number is small, the system using IFFT/FFT will suffer slightly worse performance in the presence of carrier frequency offset.

Interleaved Orthogonal Frequency Division Multiplexing (IOFDM) System

In orthogonal frequency division multiplexing (OFDM) systems, for every block of K data samples, an overhead of L samples of cyclic prefix (CP) or zero padding (ZP) is added to combat frequency selective channels. The code rate, which is defined as the ratio K/(K+L), is a measure of the efficiency of transmitting user information. In this paper, a new system is proposed to increase the code rate without increasing the number of subcarriers and without increasing the bandwidth. The proposed system considers appending the L zeros (ZP) once for every P blocks of data samples, which would increase the code rate to PK/(PK+L). It is assumed that the channel is not varying over the transmission of P consecutive data blocks. In order to recover the P data blocks in a computationally efficient manner, an interleaving scheme is proposed, and the proposed system is called the interleaved OFDM (IOFDM) system. Various issues such as computational complexity, peak-to-average power ratio (PAPR), and the effect of synchronization errors on the performance of the IOFDM system are also presented. Based on a numerical simulation study, the average bit-error-rate (BER) performance of the IOFDM system is shown to be very close to that of the OFDM system for a moderate increase in computational complexity and delay.

23 Effect of synchronization error between force and position data in moment calculations

23 Effect of synchronization error between force and position data in moment calculations

Synchronization for QPSK Transmission via Communications Satellites

Carrier phase and symbol timing synchronization performances are determined for QPSK transmission over the nonlinear communications satellite channel with several typical modem filtering configurations. A computer simulation is used that models conventional or offset QPSK transmission, the modem filters, the nonlinear satellite TWTA, and the receive modem synchronizers. These simulations are used to obtain errors in carrier phase and symbol timing estimates caused by both thermal noise and the modulation-pattern-induced jitter. The statistics of these errors are obtained for several channel filtering combinations and TWTA backoff levels. These experiments are extended to examine the overall effect of synchronization errors on bit-error probability for one particular implementation of the synchronizers.