• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1995.04b
• /
• pp.463-470
• /
• 1995

설계, 가공, 조립, 검사기술로 대표되는 생산시스템의 근간 기술은 공작기계에 의한 부품가공 소위, 기계 가공 기술이다. 가공에 필요한 NC 프로그램의 효율적인 관리를 위해 이용되던 종래의 DNC(Direct Numerical Control) 는 가공 Cell 의 효율을 높이기 위해, CNC 가공기 및 주변기기에 대한 실시간 감시/제어기능을 가진 분산제어시스템( DNC(Distributed Numerical Control)으로 발전하고있다. 본 연구에서는 이기종 CNC로 이루어진 가공 Cell에 적합 하고, 경제성, 범용성 및 확장성을 고려하여 RS485 Network 및 RS232C를 이용하여각 CNC 공작기계 및 주변기기와 연결 해서 실시간(Real Time) 동시작업(Multi Tasking) 가능한 DNC 시스템을 개발하였다.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.4A
• /
• pp.342-351
• /
• 2008

In this paper, a new handover procedure for OFDM-based multi-hop relay systems is proposed to reduce the handover overhead by distinguishing inter-cell handover event from intra-cell handover event at the level of physical layer using a hierarchical design concept of preamble. A Subcell ID concept for identifying RS in a cell is proposed in the design of hierarchical manner, in addition to the existing Cell ID for identifying BS. The decision on either inter-cell handover or intra-cell handover is made by the signal quality measure of CBINR(Carrier of BS to Interference and Noise Ratio) and CRINR(Carrier of RS to Interference and Noise Ratio), provided by the hierarchical preamble. The proposed handover procedure can simplify scanning procedure and skip/simplify network re-entry procedure (capability negotiation, authorization, registration), resulting in a significant reduction of handover overhead.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.8 no.11
• /
• pp.3876-3895
• /
• 2014

Recently, Heterogeneous Network (HetNet) with Coordinated Multi-Point (CoMP) scheme is introduced into Long Term Evolution-Advanced (LTE-A) systems to improve digital services for User Equipments (UEs), especially for cell-edge UEs. However, Radio Resource Management (RRM), including Resource Block (RB) scheduling and Power Allocation (PA), in this scenario becomes challenging, due to the intercell cooperation. In this paper, we investigate the RRM problem for downlink transmission of HetNet system with Joint Processing (JP) CoMP (both joint transmission and dynamic cell selection schemes), aiming at maximizing weighted sum data rate under the constraints of both transmission power and backhaul capacity. First, joint RB scheduling and PA problem is formulated as a constrained Mixed Integer Programming (MIP) which is NP-hard. To simplify the formulation problem, we decompose it into two problems of RB scheduling and PA. For RB scheduling, we propose an algorithm with less computational complexity to achieve a suboptimal solution. Then, according to the obtained scheduling results, we present an iterative Karush-Kuhn-Tucker (KKT) method to solve the PA problem. Extensive simulations are conducted to verify the effectiveness and efficiency of the proposed algorithms. Two kinds of JP CoMP schemes are compared with a non-CoMP greedy scheme (max capacity scheme). Simulation results prove that the CoMP schemes with the proposed RRM algorithms dramatically enhance data rate of cell-edge UEs, thereby improving UEs' fairness of data rate. Also, it is shown that the proposed PA algorithms can decrease power consumption of transmission antennas without loss of transmission performance.

• Journal of Communications and Networks
• /
• v.6 no.3
• /
• pp.216-225
• /
• 2004

In a cellular network, if there are too many data users in a cell, data may suffer long delay, and system's quality-of-service (QoS) will degrade. Some traditional schemes such as dynamic channel-allocation scheme (DCA) will assign more channels to hot (or overloaded) cells through a central control system (CC) and the throughput increase will be upper bounded by the number of new channels assigned to the cell. In mobile-assisted data forwarding (MADF), we add an ad-hoc overlay to the fixed cellular infrastructure and special channels-called forwarding channels- are used to connect mobile units in a hot cell and its surrounding cold cells without going through the hot cell's base station. Thus, mobile units in a hot cell can forward data to other cold cells to achieve load balancing. Most of the forwarding-channel management work in MADF is done by mobile units themselves in order to relieve the load from the CC. The traffic increase in a certain cell will not be upper bounded by the number of forwarding channels. It can be more if the users in hot cell are significantly far away from one another and these users can use the same forwarding channels to forward data to different cold neighboring cells without interference. We find that, in a system using MADF, under a certain delay requirement, the throughput in a certain cell or for the whole net-work can be greatly improved.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2008.05a
• /
• pp.505-508
• /
• 2008

Electrocardiogram (ECG) and blood pressure (BP) are main vital signs which are the standards in most medical settings in assessing the most basic body functions. Multi parameters are desired in providing more information for health professionals in order to detect or monitor medical problems of patients more precisely. This study urges us to develop a robust wireless healthcare monitoring system which has multiple physiological signs measurements on real time that applicable to various environments which integrates wireless sensor network technology and code division multiple access (CDMA) network with extended feature of locally standalone diagnosis algorithms that implemented in tell phone. ECG signal and BP parameter of the patients are routinely be monitored, processed and analyzed in details at cell phone locally to produce useful medical information to ease patients for tracking and future reference purposes. Any suspected or unknown patterns of signals will be immediately forwarded to hospital server using cell phone for doctors' evaluation. This feature enables the patients always recognize the importance of self-health checking so that the preventive actions can be taken earlier through this analytic information provided by this monitoring system because "Prevention is better than Cure".

• Journal of Advanced Navigation Technology
• /
• v.14 no.6
• /
• pp.859-864
• /
• 2010

In the next generation system, a study on realization of Multi-Core system is in progress for applying it in multi service network. Therefore some mobile systems are expected to be appeared. These systems can support WiBro, WCDMA, CDMA, etc with single terminal. These systems have to support various FA using broadband frequency and hand over to other service network. Especially, in the telecommunication system composed of cell, the transmit power can be interference at adjacent system, has effect on system channel capacity and cell size. In this paper, we improve the unstable transmit power caused by unsettled system operation, propose the RF(Radio Frequency) Calibration method which can use the transmit power stably even during hand over between heterogeneous networks causing unstable power change. Also we used proposed method and analysed used electricity of system during hand over between heterogeneous networks.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.25 no.6A
• /
• pp.885-892
• /
• 2000

A multi-used detector(MUD) using a radial basis function(RBF) network is proposed in a multicarrier-code division multiple access (MC-CDMA) system. In the proposed scheme, a RBF network is connected to the frequency domain in order to effectively utilize the frequency diversity. Simulations have been performed over the frequency selective and multipath fading channel. From these simulations, the proposed receiver is verified to be used for making the performance improvement in combating near-far effects and increasing the number of active users. The system capacity is increaed about 1.8 times at a BER of $10^{-3}$ under a single cell when the proposed scheme is compared with MUD using a parallel interference canceller(PIC).

• Journal of the Semiconductor & Display Technology
• /
• v.21 no.3
• /
• pp.135-139
• /
• 2022

The current-voltage modeling plays an important role in characterizing photovoltaic systems. A solar cell has a nonlinear characteristic with various parameters influenced by the external environments such as the irradiance and the temperature. In order to accurately predict current-voltage characteristics at low irradiance, the artificial neural networks are applied to effectively quantify nonlinear behaviors. In this paper, a multi-layer perceptron scheme that can make accurate predictions is employed to learn complex formulas for large amounts of continuous data. The simulated results of artificial neural networks model show the accuracy improvement by using MATLAB/Simulink.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.6 no.6
• /
• pp.1522-1545
• /
• 2012

Call admission control (CAC) plays an important role in mobile cellular network to guarantee the quality of service (QoS). In this paper, a dynamic hybrid CAC scheme with integrated cutoff priority and handoff queue for mobile cellular network is proposed and some performance metrics are derived. The unique characteristic of the proposed CAC scheme is that it can support any number of service types and that the cutoff thresholds for handoff calls are dynamically adjusted according to the number of service types and service priority index. Moreover, timeouts of handoff calls in queues are also considered in our scheme. By modeling the proposed CAC scheme with a one-dimensional Markov chain (1DMC), some performance metrics are derived, which include new call blocking probability ($P_{nb}$), forced termination probability (PF), average queue length, average waiting time in queue, offered traffic utilization, wireless channel utilization and system performance which is defined as the ratio of channel utilization to Grade of Service (GoS) cost function. In order to validate the correctness of the derived analytical performance metrics, simulation is performed. It is shown that simulation results match closely with the derived analytic results in terms of $P_{nb}$ and PF. And then, to show the advantage of 1DMC modeling for the performance analysis of our proposed CAC scheme, the computing complexity of multi-dimensional Markov chain (MDMC) modeling in performance analysis is analyzed in detail. It is indicated that state-space cardinality, which reflects the computing complexity of MDMC, increases exponentially with the number of service types and total channels in a cell. However, the state-space cardinality of our 1DMC model for performance analysis is unrelated to the number of service types and is determined by total number of channels and queue capacity of the highest priority service in a cell. At last, the performance comparison between our CAC scheme and Mahmoud ASH's scheme is carried out. The results show that our CAC scheme performs well to some extend.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37 no.1B
• /
• pp.31-38
• /
• 2012

In this paper, we propose a method to improve cell edge users' performance in HetNet (heterogeneous network) systems by cooperatively transmitting signals using remote radio heads (RRHs) located near coverage boundaries, referred to as edge RRHs. The proposed method locates the edge RRHs in specific locations of the cell boundary and provides an efficient operational strategy by adjusting the duty cycle of the edge RRHs and base stations. The effectiveness of the method is demonstrated by experimental performance based on the system model parameters of the CoMP (coordinated multi-point transmission and reception) scenario, which is discussed in LTE-Advanced (Long Term Evolution - Advanced) standard contributions. When compared with conventional methods, utilization of edge RRHs is especially advantageous for the performance improvement of lower percentile users in terms of average throughput and effectively improves the fairness among users.