• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권7호
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• pp.2530-2547
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• 2015

In the recent years, femtocell technology has received a considerable attention due to the ability to provide an efficient indoor wireless coverage as well as enhanced capacity. However, under the spectrum sharing between femtocell user equipment (FUEs) and the owner of spectrum macrocell user equipment (MUEs), both may experience higher uplink interference to each other. This paper proposes a novel distributed power control algorithm for the interference management in two-tier femtocell networks. Due to the assignment of licensed radio frequency to the outdoor macrocell users, the access priority of MUEs should be higher than FUEs. In addition, the quality of service (QoS) of MUEs that is expressed in the target signal-to-interference-plus-noise ratio (SINR) must always be achieved. On the other hand, we consider an efficient QoS provisioning cost function for the low-tier FUEs. The proposed algorithm requires only local information and converges even in cases where the frontiers of available power serve the target SINRs impossible. The advantage of the algorithm is the ability to implement in a distributed manner. Simulation results show that the proposed algorithm based on our cost function provides effective resource allocation and substantial power saving as compared to the traditional algorithms.

• Journal of Communications and Networks
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• 제15권5호
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• pp.469-475
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• 2013

In this paper, we propose an efficient interference management technique which controls the number of resource blocks (or subcarriers) shared with other cells based on statistical interference levels among cells. The proposed technique tries to maximize average throughput of a femto cell user under a constraint on non-real time control of a femto cell network while guaranteeing a target throughput value of a macro cell user. In our proposed scheme, femto cells opportunistically use resource blocks allocated to other cells if the required average user throughput is not attained with the primarily allocated resource blocks. The proposed method is similar to the underlay approach in cognitive radio systems, but resource block sharing among cells is statistically controlled. For the statistical control, a femto cell sever constructs a table storing average mutual interference among cells and periodically updates the table. This statistical approach fully satisfies the constraint of non-real time control for femto cell networks. Our simulation results show that the proposed scheme achieves higher average femto user throughput than conventional frequency reuse schemes for time varying number of users.

• 한국통신학회논문지
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• 제34권12C호
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• pp.1131-1137
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• 2009

본 논문에서는 OFDMA 기반의 디지털 이중화 방식을 위한 자원 관리 기법을 제안한다. 제안된 자원 관리 기법은 CS(Cyclic Suffix)를 사용하지 않으면서 TDoA(Time Difference of Arrival)에 의한 ISI(Inter Symbol Interference)와 ICI(Inter Carrier Interference)의 영향을 최소화 하며, SS(Subscriber Station)에 수신되는 신호의 dynamic range를 줄인다. 제안된 자원 관리 기법은 ADC(Analog to Digital Converter)의 비트 수를 줄이며, SINR(Signal to Interference and Noise Ratio)를 크게 향상시킴을 모의실험을 통하여 확인한다.

• Journal of Communications and Networks
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• 제13권6호
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• pp.664-677
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• 2011

In order to control interference and improve spectrum efficiency in the femtocell and macrocell overlaid system (FMOS), we propose a joint frequency bandwidth dynamic division, clustering and power control algorithm (JFCPA) for orthogonal-frequency-division-multiple access-based downlink FMOS. The overall system bandwidth is divided into three bands, and the macro-cellular coverage is divided into two areas according to the intensity of the interference from the macro base station to the femtocells, which are dynamically determined by using the JFCPA. A cluster is taken as the unit for frequency reuse among femtocells. We map the problem of clustering to the MAX k-CUT problem with the aim of eliminating the inter-femtocell collision interference, which is solved by a graph-based heuristic algorithm. Frequency bandwidth sharing or splitting between the femtocell tier and the macrocell tier is determined by a step-migration-algorithm-based power control. Simulations conducted to demonstrate the effectiveness of our proposed algorithm showed the frequency-reuse probability of the FMOS reuse band above 97.6% and at least 70% of the frequency bandwidth available for the macrocell tier, which means that the co-tier and the cross-tier interference were effectively controlled. Thus, high spectrum efficiency was achieved. The simulation results also clarified that the planning of frequency resource allocation in FMOS should take into account both the spatial density of femtocells and the interference suffered by them. Statistical results from our simulations also provide guidelines for actual FMOS planning.

• 재활간호학회지
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• 제3권1호
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• pp.43-58
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• 2000

Pain management is a major issue in caring of cancer patients. Patients' concerns for reporting pain and taking analgesics are patient-related barriers to the management of cancer pain. Since such study has not been done at all in Korea, it is clearly needed to study on these problems. The purpose of this study is to attain basic data in order to improve cancer pain management in Korea. This is done by: 1) examining the extent of patients' concerns that might be barriers to the optimal pain management, and the extent of related factors (pain management hesitancy, adequacy of using analgesics, pain severity and pain interference); 2) identifying the relationship between patients' concerns and the related factors. The data has been collected from 180 cancer patients who were hospitalized in medical wards of one university hospital in Seoul, Korea during the period from November 1, 1997 to February 28, 1998. The data has been collected through interviews with (1) Barriers Questionnaire - Korean Version (BQ-K); (2) Hesitancy Experience Questionnaires (HQ); (3) Pain Management Index (PMI); (4) Brief Pain Inventory (BPI); and (5) Demographic Data. The data were analyzed by descriptive statistics and by t-test, One-way ANOVA, Pearson correlation using SPSSWIN program. The Results are as following: 1) The mean scores of Pain Management Concerns (PMC) by BQ-K were toward the moderate with a little high points(2.59). Most of the patients (99.4%) had some extent of concerns (over lout of maximum 5 points). Among the eight subscales of BQ-K, the Pain Management Concerns (PMC) about 'Fear of tolerance' was the highest (3.80) and 'Worry about side effects' was the least (1.40). 2) The extent of Pain Management Hesitancy (PMH) by HQ of wnom had pain on the day of the interview was a little higher than moderate score(5.53 out of maximum 10 points). 6.7% of the patients with experiencing pain used less adequate analgesics for the severity of pain than they were expected. 27.8% of them never used any analgesics at all. The mean score of pain severity by BPI was 16.59 (maximum: 40), and that of the interference with daily life by BPI was 32.03 (maximum: 70). 3) The patients who were older, less educated, and in low socio-economic status were likely to have more concerns. Pain Management Concerns (PMC) was positively correlated with Pain Management Hesitancy (PMH) (r=.75), pain severity (r=.44) and pain interference (r=.50). Those who were not using adequate analgesics had higher Pain Management Concerns (PMC) than did those who were using adequate analgesics (t=-5.42). The patients who had more Pain Management Concerns (PMC) tended to hesitate more to report pain and to use analgesics. They used more inadequate analgesics for the severity of pain and also had experienced more pain severity and interference with daily life. In conclusion, the patients' concerns for reporting pain and for using analgesics are major patient-related barriers to cancer pain management in Korea. The patients' concerns were correlated significantly with the level of the hesitancy experience, inadequate use of analgesics, the pain severity and the interference with daily life. Considering this, an educational program for cancer patients under the treatment with analgesics should be developed in order to solve these problems.

• 한국통신학회논문지
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• 제37권5A호
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• pp.339-347
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• 2012

최근에 실내 커버리지 확장 및 광대역 데이터 서비스를 위한 가정용 기지국인 펨토셀에 대한 연구가 활발하다. 펨토셀이 배치될 때, 기존에 있던 네트워크 상황 속에서 다양한 기술적인 문제들을 발생 시킬 수 있다. 본 논문에서는 OFDMA 시스템에서 펨토 - 매크로셀 간의 간섭 완화에 대하여 연구하였고, 동적인 하향링크 자원 관리 방법을 제안하였다. 펨토셀의 전송 파워를 매크로셀로부터 오는 신호의 세기에 기반을 두어서 선택하는 방법과 펨토셀 에게 할당 할 부반송파를 동적으로 관리하는 방식을 제안하였다. 이러한 방법으로 펨토셀과 매크로셀 사용자와의 간섭을 줄일 수 있다. 제안하는 방법은 수용율을 비롯한 여러 평가 지표로 성능을 검증하였다.

• IEIE Transactions on Smart Processing and Computing
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• 제1권2호
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• pp.117-124
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• 2012

A client collaboration (CC) system is proposed for a user relay system. The proposed scheme focuses on the management of transmit power and leakage interference. In the proposed CC system, edge users transmit signals to the masters considered as user relays. The masters relay the signals of the edge users to the base station using the resource blocks (RBs) that are assigned to the edge users. The leakage interference and power consumption were analyzed in the CC system. In addition, an optimal master location problem was formulated based on the signal-to-leakage-plus-noise ratio (SLNR). Because the optimal master location problem is quite complex, a sub-optimal master location problem was proposed and a closed-form sub-optimal master location was obtained. The edge users generate smaller leakage interference and power consumption in the proposed CC system compared to the system without the CC. The numerical results showed that the edge users generate smaller leakage interference and power consumption in the proposed CC system compared to the system without the CC, and the average throughput increases.

• 한국항행학회논문지
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• 제21권4호
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• pp.359-364
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• 2017

현재 아날로그 방식의 마을방송 시스템은 기술 적용의 문제 및 시설 노후화로 인한 성능 저하 등의 문제로 인하여 무선 디지털 시스템으로의 전환과 이에 따른 시스템 표준이 요구되고 있다. 그러나 주파수 부족으로 인해 효율적인 디지털 무선 마을 방송 시스템의 구축을 위해서는 이웃마을간의 간섭분석이 중요하므로 여기서는 대표적인 간이무선국 dPMR(digital private mobile radio) 및 DMR(digital mobile radio) 방식을 고려하여 동일채널 간섭과 인접채널 간섭에 대한 시뮬레이션을 수행하였다. 동일채널 간섭분석에서는 마을간 이격거리와 인접채널 간섭분석에서는 주파수 오프셋을 사용하여 주파수 재사용 및 채널분리에 대한 본 논문의 결과는 향후 마을방송 표준개발과 시범 사업화를 위한 자료로 활용될 것이다.

• 가정과삶의질연구
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• 제26권1호
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• pp.121-135
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• 2008

This study examined influences of work-family conflict on husband-to-wife battering and explored the mediating effects of stress between work-family conflict and wife battering. Subjects were 293 male violence offenders sampled from 65 domestic violence counseling centers nationally. Both directions of conflict between. work and family, work-to-family interference (WIF) and family-to-work interference (FIW), were proven to be significantly influential on wife battering and stress. Work-to-family interference did not have direct influence on wife battering but indicated a complete mediation effect of stress. On the other hand, family-to-work interference implied a partial mediation effect of stress, with both direct and indirect influences on wife battering. Based on these findings, the research discussion was extended to include the implication of an intervention that would decrease husband-to-wife battering.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
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• 제5권5호
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• pp.103-108
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• 2016

본 논문에서는 멀티 홉 릴레이 네트워크에서 기지국(base station), 중계국(relay station)과 각 단말(mobile station)간의 전송률(throughput)을 향상시킬 수 있는 자원 할당 방법과 간섭을 겪는 단말들의 간섭을 최소화하여 모든 단말의 전송률을 보장하는 방법을 제안하고 있다. 멀티 홉 릴레이 시스템에서 기지국과 릴레이가 주파수 자원을 공유할 수 있으므로 간섭에 취약한 단말들이 생길 수 있다. 본 논문에서는 각 단말의 신호대 잡음 간섭 비(signal to interference plus noise ratio)를 이용하여 엑세스 영역(access zone)과 릴레이 영역(relay zone)의 경계를 동적으로 조절하는 기법과 함께 간섭에 취약한 단말을 분류하고 이를 관리하는 기법을 제안한다. 성능 평가를 통해 제안하는 기법이 무선자원 사용의 효율성을 향상하고 각 단말들의 공평성을 보장하며 네트워크 전체 성능을 향상시키는 것을 확인하였다.