• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.7 no.2
• /
• pp.253-270
• /
• 2013

To achieve accurate localization information, complex algorithms that have high computational complexity are usually implemented. In addition, many of these algorithms have been developed to overcome several limitations, e.g., obstruction interference in multi-path and non-line-of-sight (NLOS) environments. However, localization systems those have complex design experience latency when operating multiple mobile nodes occupying various channels and try to compensate for inaccurate distance values. To operate multiple mobile nodes concurrently, we propose a localization system with both low complexity and high accuracy and that is based on a chirp spread spectrum (CSS) radio. The proposed localization system is composed of accurate ranging values that are analyzed by simple linear regression that utilizes a Big-$O(n^2)$ of only a few data points and an algorithm with a self-calibration feature. The performance of the proposed localization system is verified by means of actual experiments. The results show a mean error of about 1 m and multiple mobile node operation in a $100{\times}35m^2$ environment under NLOS condition.

• Journal of the Institute of Electronics Engineers of Korea CI
• /
• v.44 no.4 s.316
• /
• pp.21-27
• /
• 2007

Recently cluster system built from personal computers and network devices are easily and economically constructed. Rapid technological change discloses new processors on the market yielding cluster systems heterogeneity. A parallel system in heterogeneous environment needs work managers for utilizing the full power of the heterogeneous cluster system. In this paper, we compare MPI and Cilk in a heterogeneous cluster system in terms of performance and code complexity. Experimental results show that Cilk is better than MPI with small sizes of data transfers while MPI outperforms Cilk with big sizes of data transfers. Also, We find that Cilk requires less programming efforts to write a parallel program.

• Journal of the Korean Society for Precision Engineering
• /
• v.14 no.7
• /
• pp.39-48
• /
• 1997

This paper describes the process planning system of a computer-aided design of blanking and piercing for irregularly shaped sheet metal products. An approach to the system is based on knowledge-based rules. The process planning system is designed by considering several factors, such as the complexity of blank geometry, production feasibility of products, and punch profile complexity. Therefore this system which was implemented production feasibility check and strip layout module can carry out a process planning considering a production feasibility area of both internal and external features, a dimension of blanked hole, a coner and a fillet radius for irregualrly shaped sheet metal products and generate the strip layout in graphic froms. Knowledges for process planning are extracted from plasticity theories, handbooks, relevant references and empirical know- hows of experts in blanking companies. This provides powerful capabilities for process planning system of irregularly shaped sheet metal products.

• Journal of Biosystems Engineering
• /
• v.37 no.5
• /
• pp.287-295
• /
• 2012

Purpose: Some of the most representative approaches are to apply next generation technologies to save energy consumption, fully automated control system to appropriately maintain environmental conditions, and autonomous assistance system to reduce labor load and ensure operator's safety. Nevertheless, improvement of upcoming method for soil cultured greenhouse has not been sufficiently achieved. Geometrical complexity of ground in protected crop cultivation might be one of the most dominant factors in design of autonomous vehicle. While there is a practical solution fairly enough to promise an accurate travelling, such as autonomous sprayer guided by rail or induction coil, for various reasons including the limitation of producer's budget, the previously developed sprayer has not been widely distributed to market. Methods: In this study, we developed an autonomous sprayer considering travelling performance on geometrical complexity of ground in soil cultured greenhouse. To maintain a stable travelling and to acquire a real time feedback, common wire with 80 mm thick and body frame and sprayer boom. To evaluate performance of the prototype, tracking performance, climbing performance and spraying boom's uniform leveling performance were individually evaluated by corresponding experimental tests. Results: The autonomous guidance system was proved to be sufficiently suitable for accurate linear traveling with RMS as lower than approximately 10 cm from designated path. Also the prototype could climb $10^{\circ}$ of ground's slope angle with 40 kg of water weight. Uniform leveling of spraying boom was successfully performed within $0.5^{\circ}$ of sprayer boom's slope. Conclusions: Considering more complex pathways and coarse ground conditions, evaluations and improvements of the prototype should be performed for promising reliability to commercialization.

• The KIPS Transactions:PartD
• /
• v.8D no.3
• /
• pp.233-240
• /
• 2001

As software technology is in progress and software quantification is getting more important, many metrics have been proposed to quantify a variety of system entities. These metrics can be classified into two different forms : scalar metric and metric vector. Though some recent studies pointed out the composition problem of the scalar metric form, many scalar metrics are successfully used in software development organizations due to their practical applications. In this paper, it is concluded that hybrid metric form weighting external complexity is most suitable for scalar metric form. With this concept, a general framework for hybrid metrics construction independent of the development methodologies and target system type is proposed. This framework was successfully used in two projects that quantify the analysis phase of the structured methodology and the design phase of the object oriented real-time system, respectively. Any organization can quantify system entities in a short time using this framework.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.7 no.6
• /
• pp.1327-1335
• /
• 2012

TPMS (Tire Pressure Monitoring System) is a safety assistant system to prevent the serious accident due to the damaged tire by the abnormal tire pressure. It is designed to transmit the measured data for pressure and temperature of tires from the sensor unit installed in each tire to signal processing unit installed in a vehicle. Based on the received information, a driver monitors the condition of tires using a display device, to maintain the optimum travelling condition. Since TPMS should employ the wireless communication technique, it may suffer from various interferences from external electrical or electronics devices. In order to suppress them, the beamforming techniques such as switching, minimum-variance distortionless-response (MVDR), and generalized sidelobe canceler (GSC) have been considered for TPMS. In this paper, we calculate computational complexities of three beamformers and suggest mathematical basis to compare their performance of the complexity.

• Journal of Advanced Navigation Technology
• /
• v.23 no.5
• /
• pp.424-429
• /
• 2019

The evolution of networking technology such as commercialization of 5G systems provides foundation for information exchange and control of systems over the network. In addition, importance of controlling a system with delay is increasing significantly, since various phenomena in the network are associated with delay. In this paper, with a predictive control which has been studied for designing a controller with low complexity, we propose a novel predictive control for a system with multi-inputs such that it can keeps the complexity almost the same regardless of the number of inputs and degree of delay. The asymptotic stability of the proposed control with a static output feedback is also proved. The numerical simulation shows that the proposed method is superior in complexity and the performance of finding feasible controllers to the existing predictive control and a conventional method based on augmented states.

• Journal of Advanced Navigation Technology
• /
• v.11 no.3
• /
• pp.288-295
• /
• 2007

In this paper, we proposed two systems, STTC scheme and STBC-TCM scheme, to enhance the reliability of HDR-WPAN system and analyzed BER(bit error rate) performance of the proposed systems over the slow fading channel. The proposed systems had a diversity gain and coding gain without increasing an additional channel bandwidth. However, in terms of reliability, about 4dB improvement at BER=$10^{-4}$ was obtained by the STBC-TCM scheme. In addition, HDR-WPAN system with STBC-TCM scheme had a linear rise in system complexity of ML(maximum likelihood). From the results, STBC-TCM scheme was more appropriate to improve the reliability and channel efficiency and to reduce complexity of HDR-WPAN system.

• Journal of Positioning, Navigation, and Timing
• /
• v.2 no.1
• /
• pp.1-8
• /
• 2013

A signal system for improving the code acquisition complexity of Global Navigation Satellite System (GNSS) receiver is proposed and the receiving correlator scheme is presented accordingly. The proposed signal system is a hierarchical code type with a duplexing configuration which consists of the Zadoff-Chu (ZC) code having a good auto-correlation characteristic and the Pseudo Random Noise (PRN) code for distinguishing satellites. The receiving correlator has the scheme that consists of the primary correlator for the ZC code and the secondary correlator which uses the PRN code for the primary correlation results. The simulation results of code acquisition using the receiving correlator of the proposed signal system show that the proposed signal scheme improves the complexity of GNSS receiver and has the code acquisition performance comparable to the existing GNSS signal system using Coarse/Acquisition (C/A) code.

• Journal of Intelligence and Information Systems
• /
• v.6 no.2
• /
• pp.29-40
• /
• 2000

Process planning (selection and ordering of processes) and material selection for product manufacturing are two key things determined before taking full-scale manufacturing. Knowledge on product design. material characteristics, processes, time and cost all-together are mutually related and should be considered concurrently. Due to the complexity of problem, human experts have got only one of the feasilbe solutions with their field knowledge and experiences. We propose a hierarchical expert system framework of knowledge representation and reasoning in order to overcome the complexity. Manufacturing processes have inherently hierarchical relationships, from top level processes to bottom level operation processes. Process plan of one level is posted in process blackboard and used for lower level process planning. Process information on blackboard is also used to adjust the process plan in order to resolve the dead-end or inconsistency situation during reasoning. Decision variables for process, material, tool, time and cost are represented as object frames, and their relationships are represented as constraints and rules. Constraints are for relationship among variables such as compatibility, numerical inequality etc. Rules are for causal relationships among variables to reflect human expert\`s knowledge such as process precedence. CRSP(Constraint and Rule Satisfaction Problem) approach is adopted in order to obtain solution to satisfy both constraints and rules. The trade-off procedure gives user chances to see the impact of change of important variables such as material, cost, time and helps to determine the preferred solution. We developed the prototype system using visual C++ MFC, UNIK, and UNlK-CRSP on PC.