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In cognitive radio systems, fast and efficient spectrum selection is a vital task to minimize the overhead of spectrum scanning, and hence to improve the response time of the system. So, the choice of channel sensing sequence plays an important role for better performance of the system. This paper proposes a co-operative Q-learning based spectrum sensing technique for the secondary users of an ad...
We propose an adaptive pre-compensation using second order memory less polynomial to mitigate dynamic nonlinearity in LEDs. The scheme will improve the performance of IEEE 802.15.7 standard N-level colcur shift keying (N-CSK) modulation for indoor visible-light optical wireless communication system. The N-CSK system is implemented and Voronoi segmentation is employed to decode N-CSK constellation...
This paper reports automatic segmentation of voiced, unvoiced and silence portion of speech on TIM IT data base. Waveform and frequency domain parameters are used to form multi dimensional feature space. Short time energy threshold of unvoiced segment is used to separate out silence or background from speech. The Gaussian similarity function based spectral clustering is used to find error performance...
With the advent of smarter technologies in cellular networks, often the bands used for lower versions remain unoccupied. To utilize that, in this paper, a new paradigm of cognitive radio has been proposed, where the nodes of a self-organized opportunistic ad hoc network act as the secondary users (SU) to use the white spaces of the existing cellular network. Each SU can freely move around, and in...
A time domain model of bulk InGaAs/InP uni-traveling carrier photodiode (UTC-PD) is developed in terms of integral carrier density rate equation. The wavelength dependent responsivity at different absorption width is derived from the model which shows good agreement with the experimental results. The bandwidth of the device is estimated from time dependent photocurrent response.
Performance of IEEE 802.15.7 standard indoor visible light communication employing colour shift keying (CSK) modulation has been investigated. The paper proposes a technique for non-linear compensation of transmitting LEDs to improve symbol error rate performance of the received CSK constellation of chromaticity points. Performance of field of view (FOV) angle of the LED chip is also increased due...
An electrical equivalent circuit model of InGaAs/InP uni travelling carrier photodiode is presented. The model is suitable to be built on any electrical circuit simulator to perform design and optimize the device parameters. We have shown a novel technique of increasing bandwidth of the device by inserting a small shunt inductance in series with the load without sacrificing the device output photocurrent...
We analyze the performance of IEEE 802.15.7 colour shift keying (CSK) modulation for indoor visible-light optical wireless communication system. In CSK, the combined intensity of the R, G, and B of a white LED is held constant while their relative intensities vary. Design of multilevel CSK constellation for high bit rate transmission is a challenging problem. In this work, Voroni segmentation is employed...
Detection of the spectrum holes in a cognitive radio network must be carried out very fast with minimum number of input samples. In this paper, a spectrum sensing algorithm has been proposed using compressed sensing technique which requires fewer samples than predicted by Nyquist sampling provided that the licensed user's signal must be sparse in frequency domain. An ambiguity in determining the channel...
High speed optical fiber transmission performance is severely degraded due to chromatic dispersion in the fiber. Contrary to conventional dispersion compensation techniques by dispersion compensated fiber, in this work electronic compensation techniques are investigated to mitigate chromatic dispersion in a phase modulated optical coherent detection system. Such electronic compensation techniques...
This paper proposes a method of linearity analysis of uni-traveling carrier photodiode (UTC-PD) by using an electrical circuit model of the device. Based on this circuit, third order inter-modulation products are investigated by employing two tone input signals. The resulting fundamental, inter-modulation distortion products and the third order intercept point (IP3) agrees well with reported data...
Energy detection is one of the basic schemes of spectrum sensing. In case of energy detection because of the uncertainty in estimating the noise variance there exists a fundamental limit of minimum SNR, called the SNR-wall, below which the signal could not be reliably detected. In this paper, we propose a method to overcome this SNR-wall for OFDM signal by exploiting the autocorrelation property of...
In this work we have examined Doppler induced inband crosstalk penalty and signal distortion penalty due to cascaded optical devices in a switching node in a WDM lower earth orbit (LEO) IM/DD inter-satellite network. Our analysis showed that at a given Doppler shift both the above penalties can be minimized by judiciously choosing the cascaded optical devices bandwidth of over its nominal bandwidth...
Burst mode receiver in a packet transmission through an optical fiber encounters the problem of large amplitude fluctuation among the incoming bursty data packets which causes an optical amplifier to deviate from its linearity. To mitigate this problem, an adjustable gain controlled semiconductor optical amplifier (AGC-SOA) can be employed as a preamplifier to the burst mode receiver. In this paper,...
In this work we have examined different characteristics of uni travelling carrier (UTC) photodiode (PD) by mathematical modeling of the device. Based on the basic circuit elements contain in the mathematical model, an equivalent circuit model of UTC-PD is developed. The frequency response and pulse photocurrent response agrees well with reported data. To the authors believe such kind of circuit model...
A lumped element electrical equivalent circuit model for traveling-wave semiconductor optical amplifier (TW-SOA) has been developed. The model is compatible with large signal analysis for both optical and current modulation. The novelty of this circuit model is the inclusion of wavelength dependency of gain of SOA over our earlier reported work. The paper describes dynamic response of SOA for both...
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