• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.18 no.10
• /
• pp.1142-1149
• /
• 2007

In this paper, the development of wideband MIMO channel sounder and a pilot measurement result is described for research on the multi antenna radio propagation characteristics considering urban environment at microwave frequencies. We developed $4{\times}4$ MIMO(BW:100 MHz) channel sounder using the high speed switching mechanism and periodic pseudo random binary signals method considering next generation mobile communication system. A pilot measurement campaign at the urban area of Bundang is presented for confirmation of system performance. From the analysis of measurement data, wideband path loss exponent of 3.7 and 8 GHz band is 1.79 and 1.76. Average RMS delay spread is 200 ns and 42 ns respectively. From the experiment results, operation of this measurement system is confirmed considering research for a coverage, SNR and channel capacity in urban environment at microwave frequencies.

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 1999.04a
• /
• pp.426-426
• /
• 1999

;There are many sources of uncertainty in a typical production and inventory system. There is uncertainty as to how many items customers will demand during the next day, week, month, or year. There is uncertainty about delivery times of the product. Uncertainty exacts a toll from management in a variety of ways. A spurt in a demand or a delay in production may lead to stockouts, with the potential for lost revenue and customer dissatisfaction. Firms typically hold inventory to provide protection against uncertainty. A cushion of inventory on hand allows management to face unexpected demands or delays in delivery with a reduced chance of incurring a stockout. The proposed strategies are used for the design of a probabilistic inventory system. In the traditional approach to the design of an inventory system, the goal is to find the best setting of various inventory control policy parameters such as the re-order level, review period, order quantity, etc. which would minimize the total inventory cost. The goals of the analysis need to be defined, so that robustness becomes an important design criterion. Moreover, one has to conceptualize and identify appropriate noise variables. There are two main goals for the inventory policy design. One is to minimize the average inventory cost and the stockouts. The other is to the variability for the average inventory cost and the stockouts The total average inventory cost is the sum of three components: the ordering cost, the holding cost, and the shortage costs. The shortage costs include the cost of the lost sales, cost of loss of goodwill, cost of customer dissatisfaction, etc. The noise factors for this design problem are identified to be: the mean demand rate and the mean lead time. Both the demand and the lead time are assumed to be normal random variables. Thus robustness for this inventory system is interpreted as insensitivity of the average inventory cost and the stockout to uncontrollable fluctuations in the mean demand rate and mean lead time. To make this inventory system for robustness, the concept of utility theory will be used. Utility theory is an analytical method for making a decision concerning an action to take, given a set of multiple criteria upon which the decision is to be based. Utility theory is appropriate for design having different scale such as demand rate and lead time since utility theory represents different scale across decision making attributes with zero to one ranks, higher preference modeled with a higher rank. Using utility theory, three design strategies, such as distance strategy, response strategy, and priority-based strategy. for the robust inventory system will be developed.loped.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.10
• /
• pp.209-214
• /
• 2017

The purpose of this study is to identify the factors that led greenhouse grape farms to delay their heating periods after the coming into force of the Korea-Chile Free Trade Agreement (FTA). Panel data on the cropping (system) changes from 2004 through 2016 were used for the analysis. According to the panel logistic model, the estimated coefficient of the cultivation area was 0.0002, which was statistically significant at the 10% significance level, the estimated coefficient of grape imports was 1.4258, which was statistically significant at the 1% significance level, and the estimated coefficient of the regional dummy was 0.808, which was statistically significant at the 5% significance level. The results indicated that the use of wider cultivation areas, increase in grape imports, and colder climate(in the mid-northern part of Korea) increased the likelihood of delayed heating. The Korean government is offering direct payment programs and business closure support to the greenhouse grape farmers. While these actions can relieve the damage caused by the increase in grape imports, they will not provide the ultimate solution. Various support measures are needed, such as renewing the varieties to meet the changing demand of grape consumers, providing agricultural materials to reduce the heating expenses, and modernizing greenhouse facilities to improve the energy efficiency and reduce the costs.

• Journal of Broadcast Engineering
• /
• v.22 no.1
• /
• pp.28-41
• /
• 2017

In this paper, the fast encoding algorithm in High Efficiency Video Coding (HEVC) encoder was studied. For the encoding efficiency, the current HEVC reference software is divided the input image into Coding Tree Unit (CTU). then, it should be re-divided into CU up to maximum depth in form of quad-tree for RDO (Rate-Distortion Optimization) in encoding precess. But, it is one of the reason why complexity is high in the encoding precess. In this paper, to reduce the high complexity in the encoding process, it proposed the method by determining the maximum depth of the CU using a hierarchical clustering at the pre-processing. The hierarchical clustering results represented an average combination of motion vectors (MV) on neighboring blocks. Experimental results showed that the proposed method could achieve an average of 16% time saving with minimal BD-rate loss at 1080p video resolution. When combined the previous fast algorithm, the proposed method could achieve an average 45.13% time saving with 1.84% BD-rate loss.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.37 no.8
• /
• pp.86-96
• /
• 2000

The representative area among the ones whose cost increases as the integration ratio increases is the test area. As the relative cost of hardware decreases, the BIST method has been focued on as the future-oriented test method. The biggest drawback of it is the increasing test time to obtain the acceptable fault coverage. This paper proposed a BIST implementation method to reduce the test times. This method uses an input grouping and test point insertion method, in which the definition of test point is different from the previous one. That is, the test points are defined on the basis of the internal nodes which are the reference points of the input grouping and are merging points of the grouped signals. The main algorithms in the proposed method were implemented with C-language, and various circuits were used to apply the proposed method for experiment. The results showed that the test time could be reduced to at most $1/2^{40}$ of the pseudo-random pattern case and the fault coverage were also increased compared with the conventional BIST method. The relative hardware overhead of the proposed method to the circuit under test decreases as th e size of the circuit to be tested increases, and the delay overhead by the BIST utility is negligible compared to that of the original circuit. That means, the proposed method can be applied efficiently to large VLSI circuits.

• The KIPS Transactions:PartC
• /
• v.9C no.1
• /
• pp.123-134
• /
• 2002

The requirement for QoS (Quality of Service) has become an important Issue as real-time or high bandwidth services are increasing, such as Internet Telephony, Internet broadcasting, and multimedia service etc. In order to guarantee the QoS of Internet application services, several approaches are being sought including IntServ (Integrated Service) DiffServ(Differentiated Srvices), and MPLS(Multi-Protocol Label Switching). In this paper, we describe the performance analysis of QoS guarantee mechanism using the DiffServ. To analyze how the DiffServ performance was affected by diverse input traffic models and the weight value in WFQ(Weighted Fair Queueing), we simulated and performed performance evaluation under a random, bursty, and self-similar input traffic models and for diverse input parameters. leased on the results of performance analysis, it was confirmed that significant difference exist in packet delay and loss depending on the input traffic models used. However, it was revealed that QoS guarantee is possible to the EF (expedited Forwarding) class and the service separation between RF and BE (Best Effort) classes may also be achieved. Next, we discussed the performance synthesis problem. (i. e. derived the conservation laws for a DiffServ networks, and analysed the performance variation and dynamic behavior based on the resource allocation (i.e., weight value) in WFQ.

• Journal of KIISE:Information Networking
• /
• v.29 no.4
• /
• pp.447-458
• /
• 2002

In this paper, we design and implement Wireless Transaction Protocol(WTP) and evaluate it for wireless transaction processing in mobile computing environments. The design and implementation of WTP are based on the coroutine model that might be suitable for light-weight portable devices. We test the compatibility between our product and the other products such as Nokia, Kannel and WinWAP For the evaluation of WTP, we use an Internet simulator that can arbitrary generate random wireless errors based on the Gilbert model. In our experiment, the performance of WTP is measured and compared to those of Transmission Control Protocol(TCP) and TCP for Transactions. The experiment shows that WTP outperforms the other two protocols for wireless transaction processing in terms of throughput and delay. Especially, WTP shows much higher performance In ease of high error rate and high probability of burst errors. This comes from the fact that WTP uses a small number of packets to process a transaction compared to the other two protocols and introduces a fixed time interval for retransmission instead of the exponential backoff algorithm. The experiment also shows that the WTP performance is optimized when the retransmission counter is set to 5 or 6 in case of high burst error rate.

• Korean Journal of Remote Sensing
• /
• v.34 no.6_2
• /
• pp.1229-1238
• /
• 2018

We examined if a state of sea-ice in Bering Sea acts as a prelude of variation in that of Chukchi Sea by using satellites-based Arctic sea-ice concentration time series. Datasets consist of monthly values of sea-ice concentration during 36 years (1982-2017). Time series analysis armed with Transfer entropy is performed to describe how sea-ice data in Chukchi Sea is affected by that in Bering Sea, and to explain the relationship. The transfer entropy is a measure which identifies a nonlinear coupling between two random variables or signals and estimates causality using modification of time delay. We verified this measure checked a nonlinear coupling for simulated signals. With sea-ice concentration datasets, we found that sea-ice in Bering Sea is influenced by that in Chukchi Sea 3, 5, 6 months ago through the transfer entropy measure suitable for nonlinear system. Particularly, when a sea-ice concentration of Bering Sea has a local minimum, sea ice concentration around Chukchi Sea tends to decline 5 months later with about 70% chance. This finding is considered to be a process that inflow of Pacific water through Bering strait reduces sea-ice in Chukchi Sea after lowering the concentration of sea-ice in Bering Sea. This approach based on information theory will continue to investigate a timing and time scale of interesting patterns, and thus, a coupling inherent in sea-ice concentration of two remote areas will be verified by studying ocean-atmosphere patterns or events in the period.

• Journal of Korea Multimedia Society
• /
• v.25 no.10
• /
• pp.1404-1415
• /
• 2022

The 2-dimensional arrangement method of nodes has been used in most of RF (Radio Frequency) based communication network simulations. However, this method is not useful for the an none-obstacle 3-dimensional space networks in which the propagation delay speed in communication is very slow and, moreover, the values of performance factors such as the communication speed and the error rate change on the depth of node. Such a typical example is an underwater communication network. The 2-dimensional arrangement method is also not useful for the RF based network like some WSNs (Wireless Sensor Networks), IBSs (Intelligent Building Systems), or smart homes, in which the distance between nodes is short or some of nodes can be arranged overlapping with their different heights in similar planar location. In such cases, the 2-dimensional network simulation results are highly inaccurate and unbelievable so that they lead to user's erroneous predictions and judgments. For these reasons, in this paper, we propose a method to place uniformly and randomly communication nodes in 3-dimensional network space, making the wireless link with neighbor node possible. In this method, based on the communication rage of the node, blocks are generated to construct the 3-dimensional network and a node per one block is generated and placed within a block area. In this paper, we also introduce an algorithm based on this method and we show the performance results and evaluations on the average time in a node generation and arrangement, and the arrangement time and scatter-plotted visualization time of all nodes according to the number of them. In addition, comparison with previous studies is conducted. As a result of evaluating the performance of the algorithm, it was found that the processing time of the algorithm was proportional to the number of nodes to be created, and the average generation time of one node was between 0.238 and 0.28 us. ultimately, There is no problem even if a simulation network with a large number of nodes is created, so it can be sufficiently introduced at the time of simulation.

• Land and Housing Review
• /
• v.13 no.3
• /
• pp.39-55
• /
• 2022

In this study, we investigate the interrelationship between housing tenure and childbirth by exploiting the correlation probability effect method that accounts for household heterogeneity. Using the newlywed household panel from 2011 to 2022, we find that home ownership has a positive impact on childbirth in newlyweds. Specifically, newlywed households with housing tenure show a 6.2%p higher birth rate and a 5.7%p higher second childbirth than newlywed households living in rented houses. For the case of first childbirth, we employ the probability effect probit model since the endogeneity was not detected between housing tenure and birth rate. We document the differential effects of housing tenure on childbirth in that the first childbirth rate is higher for households without housing tenures. The negative effects on first childbirth could be attributed to the economic burden due to initial housing ownership, while housing tenure could eventually provide housing stability, leading to positive effects on more than one childbirth. Finally, we identify that households with childbirth over the last year show a 4.2%p and 3.9%p lower probabilities of housing tenure in the total sample and second childbirth sample, respectively. This suggests that the increased living cost due to childbirth could delay home ownership.