• Journal of IKEEE
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• v.27 no.4
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• pp.579-586
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• 2023

Device-to-Device communication is a very important essential feature in PPDR(Public Protection Disaster Relief) communication, but it has not yet been implemented in LTE-based PPDR communication. In this study, we propose a solution to implement the LTE-based domestic PPDR communication network by evolving the terminals into D2D in-band terminals and effectively operating the current PS-LTE terminals and digital radios in the transitional period.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.3
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• pp.602-612
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• 2015

Current IEEE 802.11p which is suggested for vehicle to vehicle communication supports one hop communication. Thus, it has a limitation to carry out efficient data dissemination. In this thesis, we suggest LTE-D2D based vehicle network to provide efficient data dissemination in the vehicle environment. In this network architecture, we use name based message with IP packet options and we put the intermediate vehicle node called 'super vehicle node' and each normal vehicle node in the cell requests data to the super vehicle node. The super vehicle node responses data to the normal vehicle node. Performance analysis is based mathematical modeling. We compare LTE cellular network to LTE-D2D based vehicle network about throughput according to packet delivery time.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.19 no.2
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• pp.110-121
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• 2020

Since the number of user equipments has also increased rapidly, the problem of network load due to frequent handover of user equipments has occurred. As a solution to this we expect to be able to reduce network overload problems and the delay caused by handover using LTE-based D2D communication. In this paper, we proposed a proposal to support handover via a preceding user equipment using LTE-based D2D communication by handover method of existing LTE network. We proposed a method that can efficiently solve the handover situation of the user equipment via the preceding user equipment in order to reduce the overlapping signal used at the time of handover between the base station and the user equipment. The handover delay accompanying the change in the number of user equipments was able to confirm the result that the suggested scheme was reduced as compared with the existing LTE handover.

• KIPS Transactions on Computer and Communication Systems
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• v.4 no.1
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• pp.5-10
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• 2015

D2D (Device-to-Device) communication underlaying LTE-advanced networks is a promising technology to improve the system capacity and spectral efficiency. By sharing the same radio resources with cellular user equipments, D2D communications can significantly enhance the overall spectral efficiency. However, it may cause interference between D2D link and cellular link. Careful resource allocation and interference coordination between cellular and D2D communications are very important and need to be properly handled. This paper proposes a radio resource allocation scheme based on FFFR (Flexible Fractional Frequency Reuse) for D2D communication underlaying cellular networks. The base station selects randomly resource blocks assigned to cellular users, and reuses them for a D2D pair. Through simulations, we have confirmed that the proposed scheme improves the system throughput, reduces the computational complexity, and mitigates the interference of D2D link and cellular link.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.4 no.1
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• pp.46-52
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• 2011

In the paper, MIMO antenna for LTE 13 band, LTE 7 band wireless communication service is proposed. The proposed antenna is designed where on the top of FR-4(${\epsilon}_r=4.4$, thickness=-.8mm). In proposed structure, two Planar Inverted F Antennas (PIFAs) using meander and folded structure are symmetrically designed for the miniaturization. The isolation between two antennas was also improved by using two slits on the ground plane. The isolation values of the fabricated antenna exhibits -18 dB, -13dB at LTE 13 and LTE 7 band, respectively. The average gain and efficiency are - 4.1 dBi, 41% on LTE 13 band, -1 dBi, 81% on LTE 7 band, respectively. Thus the proposed antenna can be applied to the LTE system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.1
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• pp.19-24
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• 2014

In this paper, a multiband LTE antenna satisfying LTE octa-band is proposed. The proposed antenna consists of a modified PIFA structure and a folded monopole which has the height of 4 mm. Each parts operates at lower and upper LTE band. Measured bandwidth(6 dB return loss) was 118 MHz(870~988 MHz) at the lower band and 1,107 MHz(1,650~2,757 MHz) at the upper band. The proposed antenna has a omni-directional radiation pattern and measured peak gains were 3.21 dBi at the lower band and 4.19 dBi at the upper band, respectively. The proposed antenna is expected to be utilized for future LTE-advanced system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.3
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• pp.577-584
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• 2017

Long Term Evolution device-to-device (LTE D2D) is a key technology to mitigate data traffic load in a cellular system. It facilitates direct data exchange between neighboring users, which is preceded by D2D discovery. Each device advertises its presence to neighboring devices by broadcasting its discovery message. In this paper, we develop a mathematical analysis to assess the probability that discovery messages are successfully transmitted at the D2D discovery stage. We make use of stochastic geometry for modeling spatial statistics of nodes in a two dimensional space. It reflects signal to noise plus interference ratio (SINR) degradation due to resource collision and in-band emission, which leads to the discovery message reception probability being modeled as a function of the distance between the transmitter and the receiver. Numerical results verify that the newly developed analysis accurately estimates discovery message reception probabilities of nodes at the D2D discovery stage.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.4
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• pp.374-383
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• 2013

This paper presents a design for improvement of isolation characteristics by the inserted stub structure on ground plane of a handy terminal which is composed of a main antenna and a sub antenna covered LTE bandwidth. In order to compensate for a resonance length of proposed antenna and to realize a high isolation characteristic, a pair of stub was inserted and located on ground plane that currents from two antennas were converged. A simulated isolation characteristic of antenna without stub at the LTE class 13 band was about -5 dB, but its characteristics of proposed antenna with two stubs at uplink(777~787 MHz) and downlink(746~756 MHz) of the LTE class 13 band were about -12 dB and -15 dB, respectively. An average gain of a fabricated antenna with two stubs was observed about -2 dBi above and it showed good results with comparison of business condition that the average gain of commercial handy terminal has to appear -4 dBi above. The measured S-parameter characteristics and radiation patterns showed a reasonable agreement with the simulation results.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.517-521
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• 2018

In this paper, we designed a microstrip antenna for LTE / WLAN for wireless mobile communication high - speed communication network. The substrate of the proposed antenna is FR-4 (er = 4.3), the size is $20[mm]{\times}40[mm]$ and can be used in the frequency band of 2.77 [GHz] and 5 [GHz] Respectively. The simulation was performed using CST Microwave Studio 2014. The simulation result shows that the gain is 2.034 [dBi] at 2.77 [GHz] and 4.95 [dBi] at 5 [GHz]. The S-parameter was also found to be less than -10 [dB] (WSWR 2: 1) in the desired frequency band. The frequency bands of LTE and WLAN are widely used around the world, and the usage of the frequency is also increasing. For this reason, the dual-band antenna of LTE / WLAN is designed to help many users in a good way to use both technologies.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.1
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• pp.32-42
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• 2015

In this paper, we considered the scenario that one cellular link and muti-D2D links share the same frequency resource which can improve the spectrum efficiency during uplink communication in LTE (Long Term Evolution)-Advanced network. In order to reduce the interference caused to the D2D users, we set DME (Discovery and Management Entity) which can send the area information to eNB(evolved Node B). We proposed a resource allocation scheme by using these assistant devices to reduce the interference that CUE (Cellular User Equipment) causes to DUE Rx (D2D UE Receiver). Basing on the area information, in order to mitigate the interference among the D2D pairs which share the same frequency resource, a power control scheme has been proposed. The simulation results prove that by using the DMEs, the proposed schemes improve the stability of D2D communication and bring the highest performance of the communication system when comparing to the other different schemes.