• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.9 no.3
• /
• pp.179-185
• /
• 2009

Cognitive radio (CR), which is proposed as a technology that utilizes the frequency resources effectively, has studied to relive scarcity of the frequency resources. CR provides opportunistically unused frequency to the secondary user when the primary user is not detected. Spectrum sensing is the most important technology to detect primary user. However, in the wireless channels, according to the effect of multipath fading channel, spectrum sensing performance is compromised. Therefore, in this paper, we apply diversity scheme that is a useful technique for combating multiple fading in wireless communications. There are several classes of diversity scheme, which are time diversity, antenna diversity, muitipath diversity, frequency diversity, and so on. In this paper, we adopt antenna diversity that is a kind of space diversity. By using the proposed method, we can overcome fading effect and improve spectrum sensing performance.

• The Journal of the Acoustical Society of Korea
• /
• v.41 no.2
• /
• pp.150-158
• /
• 2022

This paper presents the results of a sea trial for very long range spread spectrum underwater acoustic communication conducted in the East Sea in September 2021. Signals were collected through 8 vertical sensors, and the range between the transmitter and receiver was about 160 km. 30 bps Multi-Code Spread Spectrum (MCSS) method and 100 bps Chirp Spread Spectrum method were used for the transmitting signal generation. The results show that when the channel coding technique was not used in a single channel, the uncoded bit error rate was high, but when the Equal Gain Combining (EGC) diversity technique was used after frame synchronization in each receiving channel, the uncoded bit error rate was reduced to 0.1 or less.

• Journal of the Korea Fashion and Costume Design Association
• /
• v.9 no.1
• /
• pp.1-11
• /
• 2007

This study suggests the new technique to express the texture that copes with the demands of the times by trying to apply the new Nuno-felt technique, to the silk, the representative material for emotion, in order to provide the basic data for the development of highly value added and competitive materials in the domestic and international markets as well as to meet the demand of consumers in the high emotion age pursuing the idiosyncrasy and qualify enhancement. Nuno-felt is the felting technique that places the wool of desired thickness on the thin fabric using wools and various kinds of fabric materials and rubs them. The samples are 3 kinds of silk including plain Chiffon with different touch, Pongee and Organza and Merino Wool, the best quality wool of wools. As a result, beyond the simple surface effect from the silk showing the superior drape feature with one color and soft wool, the Nuno-felt technique created the feminine as well as masculine, classic and modem image. Furthermore, the harmony of opacity and transparency produced the new dynamic and dimensional texture with the combination of different emotions through the visual emotion of different grey colors and rough, crude and soft touch. This study suggested the possibility that the Nuno-felt technique could create the new emotional materials for the modem sense by combining the materials with different features from the wools unlike the traditional simple felt technique.

• The KIPS Transactions:PartB
• /
• v.17B no.4
• /
• pp.303-308
• /
• 2010

In this paper, we propose a medical image registration technique combining the gradient vector flow and modified conditional entropy. The registration is conducted by the use of a measure based on the entropy of conditional probabilities. To achieve the registration, we first define a modified conditional entropy (MCE) computed from the joint histograms for the area intensities of two given images. In order to combine the spatial information into a traditional registration measure, we use the gradient vector flow field. Then the MCE is computed from the gradient vector flow intensity (GVFI) combining the gradient information and their intensity values of original images. To evaluate the performance of the proposed registration method, we conduct experiments with our method as well as existing method based on the mutual information (MI) criteria. We evaluate the precision of MI- and MCE-based measurements by comparing the registration obtained from MR images and transformed CT images. The experimental results show that the proposed method is faster and more accurate than other optimization methods.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.10 no.5
• /
• pp.113-119
• /
• 2010

In this paper, the considered cognitive radio system has a pair of PT-PR and a pair of ST-SR. In first time slot(1 Phase), PT broadcast signal $x_p$ to PR, ST and SR. Then, each receivers(PR, ST, SR) decode received signal $x_p$. In second time slot(2 Phase), ST combine decoded signal ${x_p}^{\prime}$ and signal $x_s$, and it broadcast combined signal to PR and SR. PR and SR decode combined signal. At this time, PR can achieve diversity gain, due to using MRC, it combine 'received and decoded signal ${x_p}^{\prime}$ at 1 phase' and 'detected signal $x_p$ at 2 phase'. SR use linear combining technique and it can obtain $x_s$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.7 no.2
• /
• pp.117-127
• /
• 1996

In this paper, we present the bit error performances of 4PSK and 8PSK signal transmission schemes using Maximal Ratio Combining diversity reception for m-distribution and Rician fading channels. The suitability of modeling a Rician fading environment by a properly chosen m-distribution model is examined. Using the error performance of the derived equation has been evaluated and shown in figures as a function of fading index (m), Rician factor (K), diversity branches number (L) and E($E_b/N_o$). It is found that MRC (Maximal Ratio Combining) diversity technique is very efficient for reducing the effects of fading, And then, diversity benifit much large as depth of fading becomes deeper but more decreases as many diversity branchs. Also the results show that the error performance corresponds as much as fading becomes weak and increases with the number diversty branches.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.14 no.5
• /
• pp.67-72
• /
• 2014

In this paper, an energy harvesting scheme is applied in the cooperative communication. The proposed scheme uses an energy harvesting relay in which the relay harvests the energy from the source node and transfers to the power form in forwarding the received data to the destination node. The well-known maximal ratio combining (MRC) technique is applied to increase the diversity gain at the destination. Therefore, with applying the proposed energy harvesting scheme, the limited power at the relay is solved, and the operation efficiency of the network and the mobile devices is improved. Finally, performance of the proposed protocol is analyzed in terms of bit error rate, outage probability, power collection efficiency.

• The Journal of the Acoustical Society of Korea
• /
• v.38 no.6
• /
• pp.678-686
• /
• 2019

Underwater communication performance is degraded by the influence of Inter-Symbol Interference (ISI) due to multipath. Passive time reversal processing is the most effective technique for mitigating multipath, and the diversity combining method can be used to improve its performance. This paper analyzed communication performance using the beam diversity combining method, which combines signals obtained through the beam steering to various angles. Directions of arrival were estimated through the beam-time migration, which, in turn, was estimated from probe signals received by a vertical line array. The performance was analyzed based on the number and type of combinations among the estimated angles. In this paper, the data obtained from the Biomimetic Long range Acoustic Communications 2018 (BLAC18) experiment, which was conducted in the East sea, ~50 km east of Pohang, in October 2018, were used for the analysis. The output Signal to Noise Ratio (SNR) was used as communication indicators.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.9 no.11
• /
• pp.1311-1316
• /
• 2014

To be used in a transmitter of a satellite transponder of this paper, X band 25W power amplifier module, a part constituting of high-power amplifier is transmitted to the equipment for transmitting to geostationary communications satellites(36,000Km distance). PAM consisted a total of four power amplifier module has a high output characteristic of the high-output amplifier is used in the ground station. Used in conjunction with the structured type power amplifier module is composed of Serial Combining Structure. This PAM(Power Amplifier Module) configured by combining the circuit with the power amplifier, 10 MMIC chips and the Al2O3 thin film substrate using a Hybrid Technique of power amplifier module, was implemented at X band PAM(Power Amplifier Module) of 25W grade.

• The Journal of the Acoustical Society of Korea
• /
• v.41 no.2
• /
• pp.143-149
• /
• 2022

In this paper, we evaluate the underwater frequency diversity communication performance of Selective Combination (SC) using Maximum Likelihood Estimation (MLE). In an underwater multipath frequency selective channel, destructive interference fading due to delay spread of a received signal affects the increase in error and Signal to Noise Ratio (SNR) variability of an underwater acoustic communication. Selective Combination frequency diversity using a single sensor is applied as a transmission performance improvement technique according to the frequency selectivity of a channel. In the sea experiment applying MLE for SC decision value extraction, we evaluate the performance of SC frequency diversity and MLE-SC frequency diversity. In experiment result, we confirm through experiment that the Bit Error Rate (BER) is relatively lower when the decision value extracted through MLE-SC is applied than when the SC decision value is fixed.