• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권2호
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• pp.709-730
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• 2017

To address the challenge of unprecedented growth in mobile data traffic, ultra-dense network deployment is a cost efficient solution to offload the traffic over some small cells. The overlapped coverage areas of small cells create more than one candidate access points for one mobile user. Signal strength based user association in IEEE 802.11 results in a significantly unbalanced load distribution among access points. However, the effective bandwidth demand of each user actually differs vastly due to their different preferences for mobile applications. In this paper, we formulate a set of non-linear integer programming models for joint user association control and user demand guarantee problem. In this model, we are trying to maximize the system capacity and guarantee the effective bandwidth demand for each user by soft-association control with a software defined network controller. With the fact of NP-hard complexity of non-linear integer programming solver, we propose a Kernighan Lin Algorithm based graph-partitioning method for a large-scale network. Finally, we evaluated the performance of the proposed algorithm for the edge users with heterogeneous bandwidth demands and mobility scenarios. Simulation results show that the proposed adaptive soft-association control can achieve a better performance than the other two and improves the individual quality of user experience with a little price on system throughput.

• 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.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2002년도 ICCAS
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• pp.39.4-39
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• 2002

This paper presents a design and implementation of a PID feedback control loop for micro gyroscope. The feedback control loop improves the gyroscope performance such as linearity, bandwidth, and bias stability for micro gyroscope which is basically a high-Q system and exhibits a low performance with an open loop control. The designed and implemented feed-back control loop is applied to the SNU-Bosch MEMS gyroscope to demonstrate the improvement with the feedback control loop. The bandwidth is improved to 60Hz from 25Hz of open loop control. The linearity becomes 0.5% from 1%. The bias stability is improved to 0.03 deg/sec from 0.06 deg/sec.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 춘계학술대회 논문집
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• pp.149-154
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• 2002

In a high speed spindle system, it is very important to monitor the state of rotating rotor. Particularly in active control spindle system, the position sensor must provide feedback to the control system on the exact position of the rotor. In order to monitor the state of a high speed spindle exactly, high accuracy and wide frequency bandwidth of sensors are important. This paper observes the factors which has an effect on dynamic performances of inductive position sensor.

• 한국광학회지
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• 제4권3호
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• pp.276-280
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• 1993

홀로그래픽 감광재료인 dichromated gelatin 필름을 사용하여 반사형 간섭필터를 제작하였다. 반사형 홀로그래픽 광학소자의 경우 중요한 파라미터인 회절효율, 중심파장, 그리고 대역폭의 특성을 실험을 통하여 설명하고 이들의 값을 조절하기 위한 방법을 제시하였다.

• 한국멀티미디어학회논문지
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• 제6권1호
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• pp.128-135
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• 2003

지금까지 분산-큐 이중-버스(DQDB)의 공정성을 위한 제어는 대부분 평형 트래픽, 대칭형 트래픽, 역대칭형 트래픽 같은 특정 트래픽를 대상으로 연구하였다. 본 논문에서는 이러한 특정 트래픽이 아닌 일반적인 트래픽 형태인 클라이언트-서버 트래픽 환경에서 DQDB 네트워크의 대역폭을 모든 스테이션에 공평하게 분배 할 수 있는 효율적인 제어 방식을 제안한다. 제안한 방식은 접근 임계값을 기준으로 서버에게는 APS(Access Protection Scheme)를 적용하고, 클라이언트에게는 접근 임계값만으로 대역 폭 할당을 제어한다. 시뮬레이션을 통하여 다른 방식보다 제안한 방식이 더 우수하다는 것을 확인하였다.

• 제어로봇시스템학회논문지
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• 제10권11호
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• pp.1058-1064
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• 2004

This paper presents a distributed precedence queue mechanism to resolve unexpected transmission delay of a lower priority transaction in a CAN based system, which keeps a fixed priority in data transaction. The mechanism is implemented in the upper sub-layer of the data link layer(DLL), which is fully compatible with the original medium access control layer protocol of CAN. Thus the mechanism can be implemented dynamically while the data transactions are going on without any hardware modification. The CAN protocol was originally developed to be used in the automotive industry, and it was recently applied for a broader class of automated factories. Even though CAN is able to satisfy most of real-time requirements found in automated environments, it is not to enforce either a fair subdivision of the network bandwidth among the stations or a satisfactory distribution of the access delays in message transmission. The proposed solution provides a superset of the CAN logical link layer control, which can coexist with the older CAN applications. Through the real experiments, effectiveness of the proposed mechanism is verified.

• 산업기술연구
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• 제40권1호
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• pp.19-23
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• 2020

In this paper, we proposed a PC-based CNC control system using EtherCAT-based servo drive and I/O device. The default communication of LinuxCNC is a parallel port, and data processing with high bandwidth is impossible. However, it is possible to apply various bandwidth devices through the application of EtherCAT, one of the industrial Ethernet communications with high bandwidth. Therefore, the hardware control method of LinuxCNC was applied through EtherCAT communication from the existing parallel port. Finally, through HAL configuration, I/O device operation check and 3-axis motion control proved the LinuxCNC system with EtherCAT.

• 한국통신학회논문지
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• 제19권9호
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• pp.1658-1667
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• 1994

셀룰라 이동통신 제어 시스템에서 고도의 스펙트럼 효과를 도출해 내기 위해 셀에서 호에 대한 채널을 할당하는 것은 한정된 주파수 대역폭내에서 중요한 문제이다. 이동통신 제어 시스템에 있어서는 스펙트럼 효과를 그래프 이론의 색채화 문제로 연관 시킬 수 있다. 본 논문에서는 셀룰라 이동통신 제어시스템의 그래프 이론을 이용하여 채널 오프셋 구조를 제안하고, 그래프 색채화 문제와 관련된 채널 오프셋 구조의 색체화 대역폭을 수식화 하였다. 수식화 된 채널할당 문제로부터 채널 구성에 따른 셀 설계와 보다 효율적인 주파수 스펙트럼의 최적 채널 오프셋을 연구하여 전체 스펙트럼 대역폭에 대한 상한치와 하한치를 부여 한다.

• 한국정보과학회논문지:정보통신
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• 제28권3호
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• pp.435-446
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• 2001

본논문에서는 클라이언트-서버 환경에서 DQDB-SR 네트워크 대역폭을 모든 스테이션에게 공병하게 할당하기 위한 새로운 방식을 제안하였다. 제안한 방식은 클라이언트-서버 부하 패턴의 특성을 따르는 접근 임계값과 대역폭 빌림과 반환 방식을 사용하여 DQDB-SR에게 공평한 대역폭 제어 기능을 제공한다. 이를 구현하기 위해 DQDB-SR의 처리 용량을 최대로 하는 소거 노드의 위치와 접근 임계값을 구하였다. 제안한 방식이 과부하시 클라이언트-서버 부하 패턴에 대하여 네트워크 처리 능력을 저하시키지 않고 패킷 전송 성공률과 평균 패킷 전달 지연 시간에 있어 다른 공정성 제어 방식들 보다 우수하다는 것을 시뮬레이션 결과를 통하여 확인하였다.