• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.3
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• pp.13-19
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• 2014

Improvement of performances of potable communication devices such as laptops, tablets, and smart-phones enables people to do group meetings in any place. However, even though group members in a meeting locate close, data or information to be shared in the group are exchanged through the cellular networks. This increases unnecessary traffic loads in the wireless/backbone networks and as consequence it increase delays in communications. To resolve the problem, an android-based application is developed in this paper. The application utilizes Wi-Fi Direct so that all members in the meeting can direct exchange materials for the meeting without using cellular networks.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.36C no.11
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• pp.46-54
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• 1999

The output values of cellular neural networks would have errors because they can be stabilized at local minimums depending on the initial states of each cell. So, in this paper, we design the $6\times6$cellular neural networks with annealing capability which guarantees that the outputs reaches the global minimum to have correct output values independent of the initial states of each cell. This chip is designed using a $0.8\mu\textrm{m}$ CMOS technology The designed chip contains about 15,000 transistors and the chip size is about $2.89\times2.89\textrm{mm}^2$. The simulation results of edge extraction and hole filling using the designed circuit show that the outputs values would have errors in un-annealed case, but not in annealed case. In the simulation, the annealing time of $3\musec$ is employed.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.5
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• pp.197-203
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• 2008

In this work, we present a novel genetic approach to solve the problem of combining power control and data rate transmission adjustment for the performance enhancement of the next generation CDMA system. We obtained the optimal solution of multi rate and power control problem by compromising slightly on SIR limit values. The proposed algorithm was able to handle many more users with comparable or faster convergent service. While this paper considered two kinds of fitness function such as maximizing the total transmission data rate and maximizing the acceptable mobiles of CDMA cellular network, the evaluation function combining these two cases or others can be also easily implemented. The simulation results showed the effectiveness and validity of our approach.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.5
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• pp.502-506
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• 2008

The recently proposed "Potential-based" reinforcement learning (RL) method made it possible to combine multiple learnings and expert advices as supervised knowledge within an RL framework. The effectiveness of the approach has been established by a theoretical convergence guarantee to an optimal policy. In this paper, the potential-based RL method is applied to a dynamic channel assignment (DCA) problem in a cellular networks. It is empirically shown that the potential-based RL assigns channels more efficiently than fixed channel assignment, Maxavail, and Q-learning-based DCA, and it converges to an optimal policy more rapidly than other RL algorithms, SARSA(0) and PRQ-learning.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.12B
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• pp.811-817
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• 2005

Efficient bandwidth management is necessary in order to provide high quality service to users in a multimedia wireless/mobile network. In this paper, I propose an on-line load balancing algorithm with preemption. This technique is able to balance the traffic load among cells accommodating heterogeneous multimedia services while ensuring efficient bandwidth utilization. The most important features of my algorithm are its adaptability, flexibility and responsiveness to current network conditions. In addition, my online scheme to control bandwidth adaptively is a cell-oriented approach. This approach has low complexity making it practical for real cellular networks. Simulation results indicate the superior performance of my algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.8C
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• pp.689-695
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• 2007

Wireline relay stations(RS's) are connected to cellular base stations(BS's) via radio-over-fiber(RoF) to enhance system capacity and to reduce shadow areas. Unlike wireless multi-hop systems, BS-to-RS signaling is transmitted out-of-band, thus reducing the effect of interference caused by frequency reuse. In this paper, antenna arrays used in addition to the wireline RS's are considered to evaluate the transmission capacity gain and performance variations according to the may structures. In particular, RS locations to maximize the gain, may distribution patterns for a given number of antenna elements, performance enhancement for a varying number of elements are experimentally determined to suggest a proper utilization of antenna ways in conjunction with wireline RS's.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.3
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• pp.285-297
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• 2016

In this paper, a centralized mmWave-based multi-spot beam cellular system architecture having such a base station equipped with a plurality of beam-forming antennas, multi-layered dynamic cell configuration method as one of key concepts of this system operation and a mobility management method based on it are introduced. To estimate the performance of new system, system simulation was performed under the ideal environment without blockage. These results show the possibility that system capacity can be dramatically increased and mobility performance similar to the existing cellular system may be achieved.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.39 no.3
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• pp.211-219
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• 2002

In this paper, a new architecture that can simultaneously process modular multiplication and squaring on GF(2$^{m}$ ) in m clock cycles by using the cellular automata is presented. This can be used efficiently for the design of the modular exponentiation on the finite field which is the basic computation in most public key crypto systems such as Diffie-Hellman key exchange, EIGamal, etc. Also, the cellular automata architecture is simple, regular, modular, cascadable and therefore, can be utilized efficiently for the implementation of VLSI.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.4
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• pp.570-575
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• 2001

The minimum duration outage probability of a cellular system is defined the probability that the received signal level is hold under minimum required threshold duration. This definition is more realistic compared to the outage probability which is the received signal strength level is below predefined threshold level. Especially, in a DS-CDMA cellular system the received signal-to-interference ratio is a function of cell traffic, while the former researches are only considered the minimum duration outage probability independent of the cell traffic. We noticed that the minimum outage probability is rapidly increases as cell traffic increase.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.2
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• pp.196-208
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• 2002

Since radio interference has occurred in the TRS frequency band in the south coastal area, Korea from 1994, similar interference has been observed in the mobile-cellular frequency band. Measurement showed that the sources of the radio interference are those from the base stations for digital cellular systems in Japan. This because the receiving frequency of the base stations in Korea is same as the transmitting frequency of the base stations in Japan. Since the distance between Korea and Japan is 240 ~ 300 km, we can conclude that the main reason of the interference is ducting. In this paper a ducting channel is modeled by split-step DMFT algorithm, and simulation results for measured index profile far east coast and west sea area are analyzed.