Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2018-11-29 Cooperative journals: 《计算机应用研究》
Abstract： For the intelligent algorithm, it is easy to fall into local optimum when implementing blind source separation, and the convergence speed is slow, this paper proposes a blind source separation algorithm based on Givens transform and second-order oscillator particle swarm optimization. This algorithm constructs the functional relationship between the inertia weight and the learning factor, and adjusts the algorithm together to improve the algorithm's overall and global search ability. The second-order oscillation increases the diversity of the population, so the algorithm is not easy to fall into the local optimum. In addition, the algorithm uses Givens transformation to convert the separation matrix into a rotation angle representation to reduce the complexity and accelerate the convergence speed. Simulation results show that the algorithm can effectively achieve the blind separation of mechanical vibration signals and speech signals, and has faster convergence speed and better separation performance than other algorithms
Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2018-04-24 Cooperative journals: 《计算机应用研究》
Abstract： The spectrum of the baseband spread spectrum signal has a wide frequency range, when the signal is transmitte the spectrum of the baseband spread spectrum signal has a wide frequency range, when the signal is transmitted in the band limited channel, the bandwidth of the signal needs to be limited, thereby causing intersymbol interference. Therefore, in order to reduce the inter-symbol crosstalk between baseband spread spectrum signals and their occupied bandwidth, this paper sdudy the main parameters of its low interception performance of the baseband spread spectrum signal after it passes through the pulse shaper. And pseudocode period has been estimated by using twice power spectrum. The theoretical analysis proves that the signal after twice power spectrum extends spectral line on the period of impulse sequence, and the main energy of the signal will gather in some sharpness similar to that of the quadratic spectrum of the baseband shaping pulse. The pseudo-code period of the baseband spread spectrum signal can be estimated by measuring the spacing between these sharp pulses. Computer simulation results show that the method of twice power spectrum can be used to estimate the pseudo-code period of pulse shaped spread baseband signal under low signal-to-noise ratio condition. And accuracy of the algorithm to estimate the pseudo-code period proposed in this paper improves approximately 7dB compared to the method without pulse shaping.
Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2018-04-19 Cooperative journals: 《计算机应用研究》
Abstract： In the cognitive radio(CR) environment, the problem of insufficient frequency resources gets severe, non-continuous orthogonal frequency division multiplexing (NC-OFDM) can work in the non-continuous spectral environment, this paper proposed cyclic autocorrelation method to deal with the important problem of parameter estimation of NC-OFDM signals. Firstly, analysis the characteristics of cyclostationary of signals. Then according to the cyclic autocorrelation of the NC-OFDM signal, the parameters are estimated with the characteristics of the discrete spectral lines in the cyclic frequency α and the time delay τ cutaway. Finally, this paper simulate the cyclic autocorrelation of the NC-OFDM signals. The simulation results show that the parameters of NC-OFDM signal can be effectively estimated and recognized zero-prefix orthogonal frequency division multiplexing signals(ZP-OFDM) at low signal-to-noise ratio, and the experiments show that close to 90% of the number of subcarriers, can achieve NC-OFDM signals parameter blind estimation.
Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2018-04-12 Cooperative journals: 《计算机应用研究》
Abstract： For the problem of general unambiguous acquisition for BOC (binary offset carrier) and its derivative signals is still scarce of analysis, the paper proposed an improved unambiguous acquisition method based on PCF (pseudo correlation function) . Firstly, the paper proposed the concept of step-shape bits vector to obtain a unified expression of cross-correlation function and designed two new step-shape vectors, then synthesized the received signal and referenced signal of corresponding to shape code vector to obtain a single peak. Finally, the paper obtained a generalized unambiguous acquisition method by combined the single peak and autocorrelation functions. The experimental results show that, under the same conditions, its peak energy of the main peak increases by 23% than sub carrier phase cancellation method, the new propose method can deal with all kinds of BOC signals including complex ones with different types or orders and completely eliminate the ambiguity of the autocorrelation function in the synchronization process.
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