• Journal of Korea Multimedia Society
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• v.18 no.7
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• pp.818-826
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• 2015

With the rapid interest in Geographic Information System (GIS) contents, a large volume of valuable GIS dataset has been distributed illegally by pirates, hackers, or unauthorized users. Therefore the problem focus on how to protect the copyright of GIS vector map data for storage and transmission. But GIS vector map data is very large and current data encryption techniques often encrypt all components of data. That means we have encrypted large amount of data lead to the long encrypting time and high complexity computation. This paper presents the selective encryption scheme using hybrid transform for GIS vector map data protection to store, transmit or distribute to authorized users. In proposed scheme, polylines and polygons in vector map are targets of selective encryption. We select the significant objects in polyline/polygon layer, and then they are encrypted by the key sets generated by using Chaotic map before changing them in DWT, DFT domain. Experimental results verified the proposed algorithm effectively and error in decryption is approximately zero.

• Journal of Communications and Networks
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• v.7 no.1
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• pp.13-20
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• 2005

In this paper, a new multi carrier, direct sequence code division multiple access (MC-DS-CDMA) system is proposed. Our new signal construction is based on convolutional encoding of the transmitted data, serial-to-parallel (S/P) conversion of the encoded data, Walsh-Hadamard-transformation (WHT), a second S/P conversion of the WHT outputs, spread spectrum (SS) modulation with a common pseudo-noise (PN) sequence, and then multicarrier transmission. The system bit error rate (BER) performance in frequency selective fading channel in the presence of additive white Gaussian noise (AWGN) and a jamming tone is analyzed and simulated. The numerical results are compared with those from an orthogonal MC-DS-CDMA system of Sourour and Nakagawa [7]. It is shown that the two systems have almost the same BER performance, but the proposed scheme has better anti-jamming ability.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.6
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• pp.717-721
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• 2010

In general, wireless MAC uses the ACK for reliability. Meanwhile, in wireless sensor network, data is delivered periodically and redundantly. In these situations, every ACK transmission causes the reliability flexible applications to waste some energy. IEEE 802.15.4 developed for energy efficiency has the option of using ACK or not, but there are no researches exploiting this peculiarity. In this paper, we proposed the selective unacknowledged transmission satisfying some requirements (e.g., end-to-end delivery) by removing the ACK when frames are delivered well and using the ACK when frames are delivered poorly. Also, we performed several evaluations exploiting the NS2 simulator.

• IEIE Transactions on Smart Processing and Computing
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• v.3 no.5
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• pp.338-344
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• 2014

As the role of information collection becomes increasingly important in the enormous data environment, there is growing demand for more intelligent information technologies for managing complex data. On the other hand, it is difficult to find a solution because of the data complexity and big scaled amount. Accordingly, there is a need for a special intelligent knowledge base frame that can be operated by itself flexibly. In this paper, by adopting switching function for signal transmission in the synapse of the human brain, I/E selective activation based knowledge reconfiguring mechanism is proposed for building more intelligent information management system. In particular, knowledge network design, a special knowledge node structure, Type definition, I/E gauge definition and I/E matching scheme are provided. Using these concepts, the proposed system makes the functions of activation by I/E Gauge, selection and reconfiguration. In a more efficient manner, the routing and reasoning process was performed based on the knowledge reconfiguration network. In the experiments, the process of selection by I/E matching, knowledge reconfiguration and routing & reasoning results are described.

• Journal of Korea Multimedia Society
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• v.17 no.7
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• pp.769-777
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• 2014

With the rapid interest in Geographic Information System (GIS) contents, a large volume of valuable GIS dataset has been distributed illegally by pirates, hackers, or unauthorized users. Therefore the problem focus on how to protect the copyright of GIS vector map data for storage and transmission. At this point, GIS security techniques focusing on secure network and data encryption have been studied and developed to solve the copyright protection and illegal copy prevention for GIS digital map. But GIS vector map data is very large and current data encryption techniques often encrypt all components of data. That means we have encrypted large amount of data lead to the long encrypting time and high complexity computation. This paper presents a novel selective encryption scheme for GIS vector map data protection to store, transmit or distribute to authorized users using K-means algorithm. The proposed algorithm only encrypts a small part of data based on properties of polylines and polygons in GIS vector map but it can change whole data of GIS vector map. Experimental results verified the proposed algorithm effectively and error in decryption is approximately zero.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2001.06a
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• pp.25-28
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• 2001

A new decision-feedback equalization technique for a filter bank-based orthogonal frequency division multiplexing (OFDM) data transmission system operating in a frequency selective multipath fading channel is presented in this paper. At the cost of relatively increased computational complexity in comparison to the conventional OFDM systems, the proposed system achieves a better performance in terms of bit error rates. The simulation results confirm the superiority and robustness of our method, particularly, in the low SNR channel environment.

• Journal of Information Processing Systems
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• v.13 no.1
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• pp.68-82
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• 2017

Nowadays, geographic information system (GIS) is developed and implemented in many areas. A huge volume of vector map data has been accessed unlawfully by hackers, pirates, or unauthorized users. For this reason, we need the methods that help to protect GIS data for storage, multimedia applications, and transmission. In our paper, a selective encryption method is presented based on vertex randomization and hybrid transform in the GIS vector map. In the proposed algorithm, polylines and polygons are focused as the targets for encryption. Objects are classified in each layer, and all coordinates of the significant objects are encrypted by the key sets generated by using chaotic map before changing them in DWT, DFT domain. Experimental results verify the high efficiency visualization by low complexity, high security performance by random processes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.6
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• pp.2908-2924
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• 2019

Multiple input multiple output orthogonal frequency division multiplexing (MIMO-OFDM) is widely applied in wireless communication by virtue of its excellent properties in data transmission rate and transmission accuracy. However, as a major drawback of MIMO-OFDM systems, the high peak-to-average power ratio (PAPR) complicates the design of the power amplifier at the receiver end. Some available PAPR reduction methods such as selective mapping (SLM) suffer from high computational complexity. In this paper, a low-complexity SLM method based on active constellation extension (ACE) and joint space-time selective mapping (AST-SLM) for reducing PAPR in Alamouti STBC MIMO-OFDM systems is proposed. In SLM scheme, two IFFT operations are required for obtaining each transmission sequence pair, and the selected phase vector is transmitted as side information(SI). However, in the proposed AST-SLM method, only a few IFFT operations are required for generating all the transmission sequence pairs. The complexity of AST-SLM is at least 86% less than SLM. In addition, the SI needed in AST-SLM is at least 92.1% less than SLM by using the presented blind detection scheme to estimate SI. We show, analytically and with simulations, that AST-SLM can achieve significant performance of PAPR reduction and close performance of bit error rate (BER) compared to SLM scheme.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.4 no.1 s.6
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• pp.63-71
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• 2005

This paper proposes the channel estimation method robust to severe frequency selective fading channels in O%M system using wide bandwidth for the high data rate transmission. DDCE, which uses data between the high correlated symbols, is usually used for channel estimation in the slow fading channels. DDCE can get high gains in the non-selective channels. As the bandwidth of system gets wider, it becomes more severe frequency selective fading environments so that the reliability of data becomes lower and error flow is occurred. FE method, this paper proposed, uses the relation between sub-carriers of OFDM in frequency selective fading channels so FE method gets some gains by adapting the power value at a target frequency to the mean value of channel estimated values of adjacent sub-carriers. Because FE uses only preamble unlike DDCE using data, it is independent of data rate related to the reliability of data and the number of multipath. Consequently, FE can obtain considerable gains in the wideband systems where the errorflow of DDCE is occurred, and FE is applicable to frequency selective fading environments.

• IEMEK Journal of Embedded Systems and Applications
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• v.11 no.4
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• pp.243-249
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• 2016

Energy-harvesting nodes in wireless sensor networks(WSNs) can be exhausted due to a heavy workload even though they can harvest energy from their environment. On contrast, they can sometimes fully charged, thus waste the harvested energy due to the limited battery-capacity. In order to utilize the harvested energy efficiently, we introduce a selective data compression and transmission range control scheme for energy-harvesting nodes. In this scheme, if the residual energy of a node is expected to run over the battery capacity, the node spends the surplus energy to exploit the data compression or the transmission range expansion; these operations can reduce the burden of intermediate nodes at the expanse of its own energy. Otherwise, the node performs only basic operations such as sensing or transmitting so as to avoid its blackout time. Simulation result verifies that the proposed scheme gathers more data with fewer number of blackout nodes than other schemes by consuming energy efficiently.