Teleconferencing acoustic echo cancellation using adaptive Hammerstein block structure

Özdinç, Tuğba Özge | Hacıoğlu, Rıfat


Acoustic echo in voice transmission systems severely degrades the speech quality and the speech intelligibility of speech signal due to it is formed through picking up sounds from the loudspeaker by speaker microphone. The dynamic strucure of the acoustic echo system contains cascade connection of an electro-acoustic static nonlinear system and a dynamic linear system. Hence linear models can not be successful solution to echo problem. In this paper, acoustic echo problem is mentioned and an algorithm that adapts the parameters of nonlinear Hammerstein system (cascade connection of a static nonlinearity and a dynamic linear system) . . .is suggested Daha fazlası Daha az

Change in response time of neuronal populations with noise, synaptical interactions and stimulus frequency

Özsoy, Muhammet Ali | Uzuntarla, Muhammet | Özer, Mahmut


Neurons which are the fundamental elements of the nervous system, encode the information about stimulus they received from the external world by sensory system into action potential (spike) sequences before transmitting to the brain. In this study, a neuron population is modeled in mathematical manner and then first spike appearance time in a spike train is examined against changes in the characteristics of the periodic forcing. We also examine the effect of noise which stems from the biophysical structure of neurons and the effect of synaptic coupling which is the consequence of synaptic interaction of neurons with each other in th . . .e population to the appearance time of first spikes. The obtained results show that the mean response time of the population decreases with the increasing frequency. When the intensity of inherent noise in the neuronal environment increased, it shows a decreasing effect on the mean response only for low frequency range of the stimulus. Although the synaptic interaction coefficient does not affect substantially the mean response time of the population, it was shown that it is the fundamental parameter controlling the standard deviation of the response time Daha fazlası Daha az

Performances of DS-UWB signals over the CM1 channel model

Öztürk, Ertan | Yılmaz, Ergin

Proceedings | 2007 | MobiWac'07 - Proceedings of the 5th ACM International Workshop on Mobility Management and Wireless Access , pp.107 - 111

In this paper, we investigate the probability of error performance of Direct Sequence Ultra Wide Band (DS-UWB) signals using various pulse shapes over the CM1 model of the Standard UWB channel. The considered pulse shapes are the first and second derivatives of Gauss waveform, Rayleigh waveform, and first four orthogonal modified Hermite waveforms. Results reveals that the probability of errors for all available pulse shapes over the considered channel are very similar for few users. However, by increasing the number of users, the performance differences start to appear in favor of Hermite pulses. © 2007 ACM.

Performance of direct sequence ultra wide band signals over log-normal fading channels

Öztürk, Ertan | Yılmaz, Ergin

Proceedings | 2007 | 2007 IEEE 15th Signal Processing and Communications Applications, SIU , pp.107 - 111

In this paper, the probabilities of error performances of bipolar Direct Sequence Ultra Wide Band (DS-UWB) signals are investigated over a log-normal fading channel. Since the bandwidth of UWB signals is in the level of giga Hertz, the number of the resolvable paths in the channel is large. Consequently, in the receiver, a Rake receiver in conjunction with a maximum ratio combiner is used. By using the derived probability of error expression, the numerical values of the performances are calculated for the first derivative of Gaussian, the second derivative of Gaussian, Rayleigh and Daubechies-5 (db-5) pulse signals. Results show tha . . .t the db-5 pulse based UWB system gives the best performance Daha fazlası Daha az

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