• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.8
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• pp.42-46
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• 2010

Energy detection based spectrum sensing compares the energy of a received signal from a primary user with a detection threshold and decides whether it is active or not in the frequency band of interest. Here the detection threshold depends on not only a target false alarm probability but also the level of the noise energy in the band. So, if the noise energy changes, the detection threshold must be adjusted accordingly to maintain the given false alarm probability. Most previous works on energy detection for spectrum sensing are based on the assumption that noise energy is known a priori. In this paper, we present a new energy detection scheme updating its detection threshold under the assumption that the noise is white, and analyze its detection performance. Analytic results show that the proposed scheme can maintain a target false alarm rate without regard to the noise energy level and its spectrum sensing performance gets better as the time bandwidth product of the signal used to estimate the noise energy increases.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.1
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• pp.15-20
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• 2013

An energy detection based spectrum sensing is widely known to be susceptible to the noise power uncertainty. As one of the methods to resolve this problem, a cooperative spectrum sensing based on an energy detector with double thresholds has been published recently. However, its performance analysis under a fading channel has not been carried out yet. In this paper, we present a closed form of performance analysis of the scheme by extending our previous work on evaluating the performance of an energy detector in the presence of noise power uncertainty.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.11
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• pp.22-27
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• 2011

In spectrum sensing, an energy detector compares the energy of a received signal with a predetermined detection threshold and decides whether a primary user is active or not in a licensed frequency band. Here the detection threshold is related to the noise power level in the band. Most previous works on energy detection have assumed that the noise power is exactly known a priori. However, this assumption does not hold in practice since there may be some uncertainty about the noise power. So it is necessary to investigate its effects on the performance of energy detection for spectrum sensing. In this paper, we analyze the effects using the residue theorem for contour integral and present the associated numerical results.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.3
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• pp.575-583
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• 2013

In ad hoc networks, a distributed timing synchronization is studied using a firefly-inspired approach. We illuminate the exiting synchronization algorithm based on the theory of pulse-coupled oscillators so that the algorithm can be applied to multi-carrier systems through packet-based communications, where nodes communicate over an orthogonal frequency-division multiple access air interface. As our main result, we introduce a new sync-code detector, which optimally designs both the coupling function and the detection threshold when various network parameters such as the number of nodes in the network and network topology are given a priori. Computer simulations are performed to show the convergence to a synchronized state in realistic network environments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.12
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• pp.1797-1805
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• 1993

An algorithm for the threshold decision from the maximum mismatching correlation value in a direct-sequence spread-spectrum system is presented. This algorithm is named the TDMMC(Threshold Decision from the Maximum Mismatching Correlation value). The purpose of the algorithm is to set the decision threshold in the system which will provide large probability of signal detection. Using this algorithm, the proper setting of the threshold for various SNRs is possible. An additional block called the Threshold Block is used to improve the system performance. The result from the computer simmulation has shown that appling the TDMMC to the noncoherent DS/SS-CSK system can achieve performance improvement.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.4
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• pp.1-10
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• 2001

The 3-step cell search has been considered for fast acquisition of the scrambling code unique to a cell in the W -CDMA system. In this paper, the performance of the cell search scheme is analyzed in Rayleigh fading channels. And the system parameters for cell search scheme and the design parameters for the receivers are examined. The probabilities of detection, miss and false alarm for each step are derived in closed forms based on the statistics of CDMA noncoherent demodulator output. Through the analysis, the effect of threshold setting and post detection integration for each step is investigated, and the optimal values of the power allocation for the synchronization channels are also considered. The number of post-detection integrations for each step is a design parameter for the receiver, and the optimum values may depend on not only the power allocation for each channel related to the cell search, but the false alarm penalty time. It is shown that optimal values could be determined through the analysis. Also, the cumulative probability distribution of the average cell search time is obtained.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.12
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• pp.1406-1411
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• 2012

An energy detection based spectrum sensing has been found to be vulnerable to the noise power uncertainty. A cooperative spectrum sensing with an energy detector has appeared as one of the solutions to alleviate this difficulty. However, its performance analysis in a fading environment has not been reported yet in the literature. Motivated by this, this paper presents the performance analysis of the scheme by extending our previous work on evaluating the performance of an energy detector in the presence of noise power uncertainty. The analysis shows that the false alarm probability and detection probability gets higher as the sensing time and/or the number of the secondary users in the OR based cooperative spectrum sensing scheme increase when the noise power uncertainty exists.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.1B
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• pp.90-98
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• 2002

To increase system capacity in WCDMA receiver, the coherent detection is an essential technology for recovering transmitted symbols correctly. For coherent detection, an accurate and fast channel estimation is required. In next generation mobile communication system, high frequency carriers are used, and high data rate services are provided for subscribers having high mobility. In this communication environment, however, the rapidly-changing doppler frequency degrades the quality of the transmitted signal a lot. In WCDMA system, the channel estimation is conducted using pilot channel and/or pilot symbols which are known to both transmitter and receiver. Some existing channel estimation algorithms utilize these information quite well, but the performance of channel estimation gets very poor in a complicated fading channel distorted by the doppler effect. In this paper, we propose a new channel estimation algorithm combining an early-late doppler compensator so that the doppler effect and the fading characteristics are compensated at the same time. By computer simulation, the proposed algorithm proved to be a much more efficient channel estimation method in the fast fading channel, even at reasonably low Eb/No.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.5
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• pp.55-62
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• 2019

In this paper, we consider K-user multiple-input multiple-output (MIMO) interference channel and present a transceiver design for simultaneous wireless information and power transfer (SWIPT) systems. In addition, we consider a SWIPT system where an information decoding receiver and an energy harvesting receiver are co-located at the same receiver. In the proposed scheme, signal-to-leakage plus noise ratio (SLNR) is used as a cost function and a transceiver is designed to satisfy the threshold of the harvested energy. More specifically, transmitter precoding vector, receiver filter vector, and power spitting factor are simultaneously designed to maximize SLNR with a constraint on the harvested energy. Through computer simulation, we compare the signal-to-interference plus noise ratio (SINR) performance of the proposed and conventional schemes. When a special condition among the number of transmit antennas, receive antennas, and users is satisfied, the proposed scheme showed better SINR performance than the conventional scheme at low signal-to-noise ratio (SNR) range. Also, when the condition is not satisfied, the proposed scheme showed better performance than the conventional scheme at all SNR range.