• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.16 no.6
• /
• pp.147-152
• /
• 2016

Wireless sensor networks that are easy to deploy and install are ideal for building a system that monitors the condition of the equipment in a factory environment where wiring is difficult. The ZigBee has characteristics of low price and low power compared with other wireless communication protocols and is suitable for a monitoring system requiring a plurality of nodes. ZigBee communication requires encryption security between devices because all protocol layers are based on OTM trusted by each other. In the communication between nodes, node authentication must be guaranteed and exposure of confidential information managed by each node should be minimized. The facilities of the factory are regular and stationary in distribution location. In order to protect the information gathered from the sensor in the factory environment and the actuator control information connected to the sensor node, we propose a cryptosystem based on the two - dimensional grid - based key distribution method similar to the distribution environment of the facility.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.10 no.12
• /
• pp.2221-2229
• /
• 2006

Optimal path search algorithm which is a killer application of mobile device to utilize location information should consider traffic flows of the roads as well as the distance between a departure and destination. The existing path search algorithms, however, are net able to cope efficiently with the change of the traffic flows. In this paper, we propose a new optimal path search algorithm. The algorithm takes the current flows into consideration in order to reduce the cost to get destination. It decomposes the road network into Fixed Grid to get variable heuristics. We also carry out the experiments with Dijkstra and Ar algorithm in terms of the execution time, the number of node accesses and the accuracy of path. The results obtained from the experimental tests show the proposed algorithm outperforms the others. The algorithm is highly expected to be useful in a advanced telematics systems.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.13 no.8
• /
• pp.1615-1622
• /
• 2009

Generally, the Terminal Based Navigation System(TBNS) used embedded road data searches a path that has less qualitative than The Center Based Navigation System(CBNS). TBNS has not used real time road data but it is recently able to use it with technique such as TPEG. However, it causes to increase a cost of exploring by using real time road data for improvement quality of a path, because of limited performance. In this paper, we propose a Dynamic Heuristic to improve quality of path in the TBNS. Dynamic Heuristic(DH) is not fixed data and is dynamically modified using transferred real time road data from server. In this paper, we propose path-lading algorithm with Maximum Speed Dynamic Heuristic (DH-MAX) and do an experiment. The DH-MAX is to be used the highest speed as DH, in real map divided by same size. And proposed algorithm searches path using the priority searching only of the fixed data, but also the highest speed with real time information. In the performance test, the quality of path is enhanced but the cost of searching is increased than A* algorithm.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.14 no.5
• /
• pp.1049-1056
• /
• 2010

Recently RFID system has been adopted in various fields rapidly. However, we should solve the problem of privacy invasion that can be occurred by obtaining information of RFID Tag without any permission for popularization of RFID system. To solve these problems, There is the Ohkubo et al.'s Hash-Chain Scheme which is the safest method. However, this method has a problem that requesting lots of computing process because of creasing numbers of Tag. Therefore We, suggest SP-Division algorithm satisfied with all necessary security of Privacy Protection Scheme and decreased in Tag Identification Time in this paper. And this paper implemented it in time standard finding the first key among the data devided into each nodes. The length of Hash-Chain holds 1000, and the total number of SPs increases 1000, 2000, 3000, and 4000. Comparing tag identification time by the total number of SPs and the number of Nodes with single node, extending the number of nodes to 1, 2, 3 and 4, when the number of nodes is 2, 40% of Performance, when the number of nodes is 3, 56%, and when the number of nodes is 4, 71% is improved.

• The KIPS Transactions:PartD
• /
• v.8D no.4
• /
• pp.347-360
• /
• 2001

The most expensive spatial operation in spatial databases is a spatial join which computes a combined table of which tuple consists of two tuples of the two tables satisfying a spatial predicate. Although the execution time of sequential processing of a spatial join has been so far considerably improved, the response time is not tolerable because of not meeting the requirements of interactive users. It is usually appropriate to use parallel processing to improve the performance of spatial join processing. However, as the number of processors increases, the efficiency of each processor decreases rapidly because of the disk bottleneck and the overhead of message passing. This paper proposes the method of task allocation to soften the disk bottleneck caused by accessing the shared disk at the same time, and to minimize message passing among processors. In order to evaluate the performance of the proposed method in terms of the number of disk accesses and message passing, we conduct experiments on the two kinds of parallel spatial join algorithms. The experimental tests on the MIMD parallel machine with shared disks show that the proposed semi-dynamic task allocation method outperforms the static and dynamic task allocation methods.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.12B
• /
• pp.1183-1191
• /
• 2010

In this paper, I propose an adaptive OFDM CP length algorithm for in PLC systems for smart grid. The proposed scheme calculates the channel delay information at the CP controller of the receiver by taking correlation between a received data frame and the following delayed one. The CP controller, immediately, feeds back the channel delay information to the transmitter. Then, the transmitter adapts CP length for next data frame. As an impulsive noise model, Middleton Class A interference model was employed. The performance is evaluated in terms of packet data rate, cumulative packet data rate, and bit error rate (BER). The simulation results showed data gain (which is the amount of the reduced bits) gets larger as the number of packets increase, but the amount of data gain reduced as the number of branches ($N_{br}$) increase. In respects of BER for the cases $N_{br}$ is 3, 4, and 5, performance of the adaptive CP length algorithm and the fixed CP scheme are similar. Therefore, it is confirmed the proposed scheme achieved data rate increment without BER performance reduction compared to the conventional fixed CP length scheme.

• Journal of Satellite, Information and Communications
• /
• v.3 no.2
• /
• pp.13-17
• /
• 2008

The conventional telemetry system of Korean low-earth orbiting satellites has certain limitations in accommodating various missions. As the payload becomes complex, it requires very complicated operational concepts in terms of telemetry. With the current design, the telemetry formats have to be rebuilt whenever new payloads or operation concepts are involved, and many constraints in operation shall be produced due to the lacks of its flexibility. As the capability and performance of a satellite have been improved, the communication structure of the satellite should be improved to gather more telemetry data. For the efficiency of data handling, it is necessary to change the grid based telemetry system in which the downlink interval and types for telemetry was limited. Comparing the fixed data map such as grid type, the packet based telemetry system can be operated as flexible and various types of packet can be designed such as the dump packet and the event packet. The sequence of the packets can be modified or newly defined to manage the massive satellite state of health data. In this paper, a new strategy for the telemetry development partially derived from PUS (Packet Utilization Standard) of European Space Agency, which provides enhanced features for the accommodation of payloads & operational requirements, is presented.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.46 no.10
• /
• pp.876-882
• /
• 2018

The purpose of this research is to verify the feasibility of Plastic Ball Grid Array (PBGA), one of the most popular chip packaging types for commercial electronics, under strong random vibration occurred in satellite during launch. Experiment were performed by preparing daisy chained PCB specimen, where large size PBGA were surface mounted, and the PCB was fixed to an aluminum frame which is commonly used to install the electronics parts to satellite. Then the entire sample was fixed to vibration tester. The random vibration power spectrum density employed in the tests were composed of two steps, the acceptance level of 22.7 Grms, and qualification level of 32.1 Grms with given period of time. The test results showed no solder cracks, which provided the strong structural integrity and feasibility evidences of the PBGA packaging to aerospace electronics. Numerical analyses were also performed to calculate the solder stresses and analyze their development mechanism.

• Journal of KIISE:Computing Practices and Letters
• /
• v.14 no.3
• /
• pp.316-320
• /
• 2008

Data dissemination schemes for wireless sensor networks, where sinks and event targets might be mobile, has been one of the active research fields. For doing that, stationary nodes gathered data on behalf of mobile sinks and the relayed data in previous studies. their schemes, however, lead to frequent query flooding and report congestion problems over sink moving. We propose a data dissemination protocol to solve both the query flooding and the report congestion problem. Our scheme improves the two shortcomings through sink location management. Finally, we prove effectiveness of our protocol through computer simulations.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.17 no.4
• /
• pp.607-616
• /
• 2022

A new axial flux permanent magnet machine with soft magnetic composited cores is proposed for electric vehicle application in this paper. The windings and soft magnetic composited cores can be designed to form a very compact structure, and; thus, the torque density can be improved greatly. To obtain the a good flux concentrating ability, two toroidally wound internal stator machines are designed and analyzed, and the designed motor is with NdFeB magnet for high-performance electric vehicle application. The 3-D finite-element method is used to analyze the electromagnetic parameter and performance, for performance comparison, a commercial axial flux permanent magnet machine is used. The proposed motor reduced weight about 5.8%, produced torque higher than about 8Nm for existing motor.