• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.6
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• pp.19-25
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• 2009

The performance of a cognitive radio system with cooperative diversity which includes the direct and indirect path is analysed. The selection relay cooperation which selects the best relay, the relay with the best received signal-to-noise ratio(SNR) in destination node, is considered and derived the performance degradation caused by the CSI(Channel State Information) delay analytically. Numerical examples show that the cooperative diversity which have the direct and the indirect paths effectively improves the system performance in Rayleigh fading; the performance improves 4.4 dB with 1/10 of SNR of the indirect path. And the system performance is more degraded with the less frequency acquisition probability and with the high CSI delay.

• Journal of Broadcast Engineering
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• v.17 no.2
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• pp.262-269
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• 2012

Hybrid-ARQ and opportunistic relaying are the widely used schemes for obtaining diversity gain in wireless communications. In opportunistic relaying, channel state information(CSI) between relays and destination is required to select the best relay. But if the destination moves very fast, the CSI becomes outdated. In this paper, performance of hybrid-ARQ based opportunistic relaying with outdated CSI is analyzed in outage probability and throughput perspective. The analysis is verified by computer simulations.

• Journal of Communications and Networks
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• v.15 no.4
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• pp.352-361
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• 2013

Combining multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) with a massive number of transmit antennas (massive MIMO-OFDM) is an attractive way of increasing the spectrum efficiency or reducing the transmission energy per bit. The effectiveness of Massive MIMO-OFDM is strongly affected by the channel state information (CSI) estimation method used. The overheads of training frame transmission and CSI feedback decrease multiple access channel (MAC) efficiency and increase the CSI estimation cost at a user station (STA). This paper proposes a CSI estimation scheme that reduces the training frame length by using a novel pilot design and a novel unitary matrix feedback method. The proposed pilot design and unitary matrix feedback enable the access point (AP) to estimate the CSI of the signal space of all transmit antennas using a small number of training frames. Simulations in an IEEE 802.11n channel verify the attractive transmission performance of the proposed methods.

• Journal of the Korea Society of Computer and Information
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• v.11 no.1 s.39
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• pp.35-44
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• 2006

As the E-commerce and E-business are developed actively, using certificate is incremented rapidly. The certificate validation must be confirmed at first in E-commerce and the OCSP Responder can offer CSI to the client using OCSP. With the rapid development of the E-commerce based on the Internet, a lot of clients request CSI to OCSP Responder. So, the load to OCSP Responder is increased and the OCSP Responder may be overloaded. Therefore, for distributing the load to an OCSP Responder, D-OCSP is introduced. As the CRL has a lot of information about revoked certificates and have a high exposure Possibility of information in the process of distribution, the confidentiality as well as integrity are required in the process of distribution. So, we propose a CRL distributing method based on group key agreement in D-OCSP. The proposed method can distribute effectively a published CRL to OCSP Responders with confidentiality as well as integrity and offer concurrency that each OCSP Responder can start CSI servicing of new CRL to clients at the same time.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.3
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• pp.229-235
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• 2010

The Orthogonal Frequency Division Multiplexing(OFDM) has been strongly recommended as a transmission technique in order to satisfy requests of high speed and high quality multimedia information. This paper considers resource allocation algorithm which supports the user Quality of Service(QoS) for multi-user OFDM system with simple CSI (Channel State Information) structure. After users eligible for services and the number of subcarrier are determined by minimum request data rate and average channel gain, subcarriers are allocated to increase total transmission rates. Although ideal CSI is not reported to base station, compared to conventional algorithm, we have obtained better result with simple CSI structure.

• Clinics in Shoulder and Elbow
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• v.26 no.1
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• pp.49-54
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• 2023

Background: Lateral epicondylitis is an increasingly debilitating condition in working population. Evidence for conservative treatment modalities has been inconclusive. Percutaneous pie crusting of the common extensor origin at the lateral epicondyle at the time of local corticosteroid injection (CSI) has been proposed sparsely. The objective of this study was to analyze if concomitant CSI and pie-crusting of the common extensor origin provides better outcome than CSI alone in lateral epicondylitis. Methods: This case-control study on 236 patients was conducted at a single center between January 1, 2020, and May 31, 2022. Patients were divided into two groups (n=118 each) based on their preference. Group A underwent CSI alone and group B underwent pie crusting along with CSI. The clinical and functional outcomes of all patients were evaluated at 2, 4, 6, and 12-week post-procedure using the visual analog scale (VAS) and Nirschl score. The mean time for return to daily activities was also compared. Results: Both groups showed significant improvement in post-procedure outcome at successive follow-ups on intragroup longitudinal analysis (VAS: F=558.384 vs. F=1,529.618, Nirschl: F=791.468 vs. F=1,284.951). On intergroup analysis, VAS of group B was superior to that of group A; however, it was statistically significant (P<0.05) only from the 6-week follow-up onwards. Nirschl score of group B was significantly better throughout the period of follow-up (P<0.05). Group B returned to daily activities faster than Group A (6.2±0.44 weeks vs. 7.18±0.76 weeks). Conclusions: Concomitant pie crusting with CSI is recommended for lateral epicondylitis as it provides significantly better results than CSI alone.

• The Science & Technology
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• s.528
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• pp.13-15
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• 2013

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.11
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• pp.2616-2635
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• 2013

In this paper, we propose an iterative transceiver design in a multi-relay multi-user multiple-input multiple-output (MIMO) system. The design criterion is to minimize sum mean squared error (SMSE) under relay sum power constraint (RSPC) where only local channel state information (CSI)s are available at relays. Local CSI at a relay is defined as the CSI of the channel between BS and the relay in the $1^{st}$ hop link, and the CSI of the channel between the relay and all users in the $2^{nd}$ hop link. Exploiting BS transmitter structure which is concatenated with block diagonalization (BD) precoder, each relay's precoder can be determined using local CSI at the relay. The proposed scheme is based on sequential iteration of two stages; stage 1 determines BS transmitter and relay precoders jointly with SMSE duality, and stage 2 determines user receivers. We verify that the proposed scheme outperforms simple amplify-and-forward (SAF), minimum mean squared error (MMSE) relay, and an existing good scheme of [13] in terms of both SMSE and sum-rate performances.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.5
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• pp.17-23
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• 2012

Recently, for spectral efficiency and power saving, an incremental best relay selection of a cooperative diversity scheme is proposed. However during the best relay selection process, there may exist a delay between channel estimation and actual data transmission. Consequently, this delay causes outdated channel state information (CSI). We analytically derive the effect of the outdated CSI to an incremental best relay selection diversity scheme. It is noted that the system performance deteriorates with decreasing the value of the correlation coefficient sensitively. When the correlation coefficient reduces from 1 to 0.9, the most performance degradation is denoted. However, the performance degradation is diminished with decreasing the correlation coefficient.

• Journal of the Korean Dietetic Association
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• v.4 no.2
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• pp.152-159
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• 1998

The purpose of this study was to compare the customer satisfaction index(CSI) between 8 self-operated foodservices and 6 contract foodservices in Pusan and the Kyeung Nam area. There were 438 subjects for self-operated foodservices, and 384 for contract foodservices. The questionnaire was used in this study as a survey method and was concerned with quality of food(Ⅰ)(Ⅱ), sanitation, facilities, information service, and employee sevice area. Data from customers were analyzed by using the $SPSSPC^+$ program, and in terms of frequency, and t-test. The results are as follows; 1. Sanitation was the most important factor in both self-operated and contract foodservices. 2. Contract foodservices showed a higher mean rating in both facilities and employee service than did self-operated foodservices in the satisfaction. 3. In self-operated foodservices, men had a significantly(p>0.05) higher CSI in all areas then women, but contract foodservices did not have this difference. 4. Contract foodservices had a higher CSI in quality of food(Ⅰ), sanitation, facilities, information service, and employee service area, and was also in higher total CSI, than self-operated foodservices.