• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.2
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• pp.380-384
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• 2015

As an extension of Visible Light Communication, Optical Camera Communications (OCC) will be a promising service for smart devices. Especially in line of sight marketing service and indoor localization application, by using camera which exists in smart devices, small amount of data (url link) can be broadcasted or find direction from the illumination system. This paper introduces the operation of wireless communications technology that transmits optical information from optical light source to camera, called Optical Camera Communications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.3A
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• pp.287-295
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• 2011

Cognitive radio (CR) features opportunistic access to spectrum when licensed users (LU) are not operating. To avoid interference to LU, cognitive users (CU) need to perform spectrum sensing. Because of local shadowing, fading, or limited sensing capability, it is suggested that multiple CUs cooperate to detect LU. In cooperative spectrum sensing, CUs should exchange their sensing data with minimum bandwidth and delay. In this paper, we introduce a novel method to efficiently report sensing data to the central node in an infrastructured OFDM-based CR network. All CUs simultaneously report their sensing data over unique and orthogonal signals on locally available subcarriers. By detecting the signals, the central node can determine subcarrier availability for each CU. Implementation challenges are identified and then their solutions are suggested. The proposed method is evaluated through simulation on a realistic channel model. The results show that the proposed method is feasible and efficient.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.12A
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• pp.1015-1023
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• 2011

In maritime communication, QoS problem caused by routing is very important. In this paper, we propose a method based on AOMDV protocol providing a route recovery mechanism when a link breaks in an active route to reduce lost packets. The results show that the proposed method can reduce packet loss ratio and delay time compared with the AOMDV.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.7A
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• pp.635-639
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• 2011

As LED becomes more important in lighting system, LED-based communication draws much attention. Only a single color has been used for this purpose thus far. However, as emotional lighting becomes more important, the need for color visible light communication is growing. In this paper, a transmission scheme for RGB color based communication is proposed that can transmit data while changing color constantly.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.7A
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• pp.649-653
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• 2011

This paper basically considers a space-division multiple-access (SDMA) systems where all nodes including the base station and mobile stations are equipped with equal number of antennas. In the SDMA system, for each transmit antenna, the user corresponding to the largest signal-to-interference-plus-noise (SINR) is selected to be supported. In this environment with the minimum mean squared error receivers, we analyze the average throughput using the previous works.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.3B
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• pp.231-239
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• 2011

This paper reviews the recent theoretical and empirical studies on the European countries that the bill and keep settlement between mobile operators is superior to the financial settlement like CPNP from the perspectives of social welfare and fare competition in market. Besides these the recent studies, considering the change of mobile wholesale market in Korea, the necessity to introduce the bill and keep settlement as an alternative for the current CPNP as well as policy implication is examined.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.3B
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• pp.214-219
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• 2011

The IMS (IP Multimedia Subsystem) is used for providing multimedia services to network provider. The IMS is composed of many nodes, depending on their function. According to the status (fault, performance, etc.) of each node, we need to provide dynamic routing algorithm. In this paper, we propose a dynamic routing algorithm for management of the IMS nodes using SNMP based on FCAPS (Fault, Configuration, Accounting, Performance and Security) in the IMS network.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.7B
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• pp.550-564
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• 2012

In this work we propose a new pricing scheme for the wireless Internet services over WiMAX system. First, let us review the characteristics of wireless network which is based on multi-hop relay WiMAX system. Next, we show why usage-based and QoS-aware pricing scheme is needed in the wireless Internet. After that, we propose a theoretical model for the price of multimedia services called a DAP (DiffServ-aware pricing) scheme for the WiMAX multimedia network which takes into account the consumed radio resource of WiMAX system as well as the supported QoS in the IP backbone network. Finally, we present explicit formulae for the packet price, price of consumed radio resource, and price of consumed bytes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.3
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• pp.188-190
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• 2014

In mobile ad hoc networks(MANETs), each node rebroadcast received route request packets for route discovery. Flooding from large number of nodes induces the broadcast storm problem which causes severe degradation in network performance due to redundant retransmission, collision and contention. This paper presents a node status algorithm based on probabilistic scheme to alleviate the broadcast storm problem for wireless ad hoc networks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.11
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• pp.1114-1121
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• 2014

Armed forces conducts war under volatile and unpredictable situation. Constructing communication system which ensures a victory is very important and difficult work. Traffic modeling has been conducted to derive WNW topology which meets operational requirements and capability under tactical environment. The result of study explains based on DTaQ's IER that company level cluster has 10~20% better packet receive rate than brigade level size.