• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1459-1462
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• 2002

Emergence of the fourth generation mobile communication system (4G system) is now in its dawn. This paper pro- poses a perspective framework on the 4G system, and discusses system aspects of radio access technologies. The focus of the paper is to define the scope and features of the 4G system in an overall system/network viewpoint. From the foreseeable development trends, it is highly expected that whatever emerges in the 4G system will be some kind of constantly evolving and grand recursive concatenation of all the existing system/network developments.

• Korean journal of communication and information
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• v.78
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• pp.79-115
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• 2016

This study, by proposing a case study of community radio, attempts to expand the horizon of academic and social discussion on the medium that has been disproportionately skewed towards discourses on alternative media, technology, and programming content. As residents of local community actively participate in the production process, they reconstruct their cultural identities. In that sense, community radio is a medium that makes it possible the re-negotiation and reconfiguration of cultural identities of local residents. That is to say, a case study on the specific ways in which community residents appropriate community radio in reconstructing their identities offers us some entry points where we may come up with a new perspective on the identity of community radio. The results of fieldwork show that community radio, as it is closely intertwined with the residents' participatory cultural practices, is a medium of 'lived culture' -i.e., a medium that contributes to the making of civility, communitarianism, and social network. Community radio, then, may be redefined as an interactive medium that contributes to the formation of social rapport and solidarity.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.1
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• pp.35-41
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• 2017

To solve the shortage of radio spectrum and utilize spectrum resource more efficiently, cognitive radio technologies are proposed, and many studies on cognitive radio have been conducted. Multi-hop routing is one of the important technologies to enable the nodes to transmit data further with lower power in ad-hoc cognitive radio networks. In a multi-channel cognitive radio networks, each channel should be allocated to minimize interference to primary users. In the multi-hop routing, channel allocation should consider the inter-channel interference to maximize network throughput. In this paper, we propose multi-channel scheduling scheme which minimizes inter-channel interferences and avoids collision with primary users for the multi-hop multi-channel cognitive radio networks. The proposed scheduling is designed to determine both of routing path and channel selection. The performance of proposed channel allocation scheme is evaluated by the computer simulation in the aspect of capacity and collision rate.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.9
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• pp.62-66
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• 2016

This paper presents a MedRadio-band low power low noise amplifier for Medical Devices. A proposed MedRadio-band low power low noise amplifier adopts a current-reuse resistive feedback topology to increase overall gm and reduce power consumption. The gain of the LNA increases by the Q-factor of the additional series RLC input matching network, and its noise figure is minimized by the similar factor. Furthermore, it consumes low power because of low supply voltage and current reuse technique. By exploiting the $g_m$-booting and matching network property, the proposed MedRadio-band low noise amplifier achieves a noise figure of 0.85 dB, a voltage gain of 30 dB, and IIP3 of -7.9 dBm while consuming 0.18 mA from a 1 V supply voltage in $0.13{\mu}m$ CMOS technology.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.11
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• pp.1574-1580
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• 2021

This paper designs and presents the results of an air network simulation radio transmission link applied with a multi-beam active phase array antenna simulator in a testbed system for verifying an air network currently underway as a technology development task. Using the Ku band, the Radio transmission link was designed in consideration of the link budget to satisfy the requirements for the system being developed. Considering short-distance links and long-distance links, the required EIRP and G/T performance scales of multi-beam repeaters and mission planes were applied to confirm the minimum and maximum link margins based on Eb/No. In this Radio Transmission Link design, the application analysis results such as rainfall availability are used to effectively establish standards when selecting the operating radius of the multi-beam relay system and related system standards.

• Current Optics and Photonics
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• v.4 no.4
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• pp.310-316
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• 2020

We propose and experimentally demonstrate an all-optical radio frequency (RF) spectrum broadening system based on time compression. By utilizing the procedure of dispersion compensation values, the frequency domain is broadened by compressing the linear chirp optical pulse which has been multiplexed by the radio frequency. A detailed mathematical description elucidates that the time compression is a very preferred scheme for spectrum broadening. We also report experimental results to prove this method, magnification factor at 2.7, 8 and 11 have been tested with different dispersion values of fiber, the experimental results agree well with the theoretical results. The proposed system is flexible and the magnification factor is determined by the dispersion values, the proposed scheme is a linear system. In addition, the influence of key parameters, for instance optical bandwidth and the sideband suppression ratio (SSR), are discussed. Magnification factor 11 of the proposed system is demonstrated.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.9
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• pp.1654-1662
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• 2006

An ad hoc network is multi-hop network composed of radio links. and the transmission quality of a radio link is more unstable than that of a wired circuit. Packet loss thus occurs frequently in an ad hoc network, and the consequent connection failure results in a severe deterioration of TCP performance. TCP performance also deteriorates because of the collision of data packets and ACK packets in the radio channel. In this paper we study to improve the performance of the Mobile Ad-hoc network by using Delayed ACK algorithm with our proposed ODA(Ordering-Delayed ACK) method. The proposed ODA algorithm increases the number of the data packets orderly at the receiver side which is going to be applied for the Mobile Ad-hoc network. We accomplished a computer simulation using NS-2. From the simulation results, we find the proposed ODA algorithm obviously enlarge the channel capacity and improve the network performance at the situation of multi-hop of ad-hoc network than the existing Delayed ACK algorithm.

• Journal of KIISE:Information Networking
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• v.36 no.3
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• pp.163-172
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• 2009

Various terminals equipped with multiple interfaces may receive services from wireless networks when they pass through the overlaid heterogeneous networks, and thus the vertical handovers across the wireless networks increases, which will become a big problem in the network resource management. This problem can be efficiently solved by common radio resource management (CRRM). In this paper, we propose two operation algorithms based on network selection jointly with vertical handover as the key CRRM strategies. When a new user tries to get services, the CRRM can choose the best target network according to the proposed Integrated Network Selection Algorithm. When the network cannot satisfy the request from the new users, the proposed Integrated Vertical Handover Algorithm moves existing users to neighborhood networks to accommodate new users. The performance of the proposed algorithms has been validated through extensive simulations.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.1
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• pp.60-66
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• 2009

A service network in the future ubiquitous environment can consist of a variety of elements, which include different protocols of the network transport. Interwoking different transport protocols can alleviate such problems occurred in accessing network as poverty of facilities, faults, and contention in a path of particular protocol communication. This paper schemes to improve performance of the network constituted of different protocols for the network transport. Interposing an interwork element, like SDR (Software Defined Radio), in the network can raise availability of transport paths, and then improve transport performance of the overall network Simulation analysis justifies such a scheme and this paper presents simulation results.

• The Bulletin of The Korean Astronomical Society
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• v.34 no.2
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• pp.37.1-37.1
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• 2009