• Electronics and Telecommunications Trends
• /
• v.30 no.3
• /
• pp.84-94
• /
• 2015

5G와 IoT로 인한 무선 트래픽 급증에 대응하기 위해서는, 무선망 성능 및 주파수효율 향상, 신규주파수할당, 주파수 공동사용 기술 개발 등이 복합적으로 적용되어야 달성 가능하다. 그의 일환으로, LTE를 비면허 대역에 사용하려는 LTE-U(Long Term Evolution-Unlicensed)라는 새로운 패러다임의 수평적 주파수 공동사용 기술을, 이동통신에 적용하려는 시도가 진행되고 있다. LTE-A의 주파수 집성기술을 활용하여, 1차 캐리어를 면허 대역 LTE 기반으로 하고, 2차 캐리어를 비면허 대역 LTE로 묶어서 고속으로 데이터를 전송하는 기술이다. 우선적으로 5GHz 비면허 대역에 적용을 검토하고 있는데, 기존에 사용하던 Wi-Fi 및 기상레이다 등과의 공정한 공존(fair coexistence)이 가장 중요하다. 따라서 각국의 5GHz 주파수 대역 규제 현황, 공존을 위한 LBT(Listen-Before-Talk)통신 메커니즘, 표준화 현황을 살펴본다. 또한 이해 당사자인 Wi-Fi, LTE, 이용자, 기술기준의 입장을 살펴보고, 구현이슈, 지적소유권 동향 등을 검토하고, 기술적 및 정책적 대응전략을 살펴본다.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.23 no.5
• /
• pp.131-138
• /
• 2023

In this paper, a free space optical communication device that can be used in a mobile base station of several km or less was fabricated and its characteristics were investigated. To overcome the loss due to atmospheric transmission, an optical fiber amplifier (EDFA) with an output of 23 dBm or more was used. In order to increase the focusing speed and miniaturization of the laser beam, an optical lens was manufactured, and a transmission lens was designed to have beam divergence within the range of 1.5 to 1.8 [mrad]. A PT module that controls PAN/TILT was fabricated in order to reduce pointing errors and effective automatic alignment between transceiver devices. In this study, Reed-Solomon (RS) code was used to maintain the transmission quality above a certain level. It was manufactured to be able to communicate at a wireless distance of 300m in a weather situation with visibility of 300m. For performance measurement, it was measured using BERT and eye pattern analyzer, and it was confirmed that BER can be maintained at 2.5Gbps.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.10 no.5
• /
• pp.557-564
• /
• 2015

In this paper, the compact antenna for handsets is designed using FR-4 substrate for LTE(905-960 MHz), WCDMA(1922.8-2167.2 MHz), DCS(1710.2-1879.8 MHz), US-PCS(1850.2-1989.8 MHz), WLAN(2400-2483 MHz). The CPW line with many advantages and a spiral geometry for miniaturization is proposed. Widths of a spiral line are constant, and three stubs are added to broaden the bandwidth. Lengths and widths of three stubs are gradually changed. And proposed antenna is optimized for VSWR<3, designed, and fabricated. The dimension of this antenna is only $40{\times}30{\times}1mm3$ which is compact. It has been demonstrated by experiment that the compact planar antenna can be used as the mobile communication LTE antenna for 4G.

• Journal of Advanced Navigation Technology
• /
• v.26 no.2
• /
• pp.91-98
• /
• 2022

Unmanned aircraft system traffic management (UTM) service for the safe operation of unmanned aerial vehicles (UAV) such as drones using commercial communication networks such as long-term evolution (LTE) and 5G in low-altitude areas of 150m or less is being studied in several countries. In this paper, whether it is possible to secure three-dimensional (3D) coverage for UTM service using the existing LTE cellular network for terrestrial usersis analyzed through simulations. The practicality in the real environment is confirmed by performing performance analysis in the actual topographical environment and the LTE base station layouts in Korea. According to the analysis results, as the altitude increases, the number of line-of-sight (LOS) interference base stations increases, resulting in a worse signal to interference plus noise ratio (SINR), but coverage is secured except for the limited areas within 150m. was confirmed to be possible. In addition, it is confirmed that a significant proportion of outage areas could be reduced by placing a small number of additional base stations for the outage area.

• Journal of Digital Convergence
• /
• v.20 no.3
• /
• pp.63-68
• /
• 2022

This After the debut of 5G, our lives have changed a lot. In particular, the proliferation of wireless network services through smartphones and LTE has completely changed the existing mobile communication services that are limited to voice/text communication between individuals and individuals, and new innovative services have emerged in all aspects of personal and corporate activities. This study verified the relationship between the social characteristics of 5G services and users' willingness to use 5G services. It analyzed the influence relationship between independent variables (social reality, subjective norms), media variables (perceived usefulness) and dependent variables (use intention), set hypotheses, and identified the media effects of perceived usefulness. The measurement items of variables are defined, and the research model of 5G service usage intention is designed. A questionnaire survey was conducted on the measurement items for users who have experience in using 5G services. Based on this result, among the social factors of users of 5G services, social reality and subjective norms are suitable factors to improve users' intentions. And through this research we put forward the enlightenment, discussed the limitations of the research and future research directions.

• Convergence Security Journal
• /
• v.19 no.1
• /
• pp.3-10
• /
• 2019

The 5G network is a next-generation converged network that combines various ICT technologies to realize the need for high speed, hyper connection and ultra low delay, and various efforts have been made to address the security vulnerabilities of the previous generation mobile networks. However, the standards released so far still have potential security vulnerabilities, such as USIM deception and replication attack, message re-transmission attack, and race-condition attack. In order to solve these security problems, this paper proposes a new 5G-AKA protocol with PUF technology, which is a physical unclonable function. The proposed PUF-based 5G-AKA improves the security vulnerabilities identified so far using the device-specific response for a specific challenge and hash function. This approach enables a strong white-list policy through the addition of inexpensive PUF circuits when utilizing 5G networks in areas where security is critical. In addition, since additional cryptographic algorithms are not applied to existing protocols, there is relatively little burden on increasing computational costs or increasing authentication parameter storage.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.14 no.5
• /
• pp.805-810
• /
• 2019

Recently, a majority of 4G mobile telecommunication manufacturers prefer repeaters with good adaptability. In this paper, we propose a new LMF(: Least Means Fourth) algorithm for LTE(: Long Term Evolution) RF(: Radio Frequency) Repeater. The proposed algorithm is a modification of the LMF, which appropriately adjusts the step size and improves performance according to the Sign function. The steady state MSE(: Mean Square Error) performance of the proposed LMF algorithm with step size of 0.009 is low level at about -25dB, and the proposed LMF algorithm requires 500 less iterations than the conventional algorithms at MSE of -25dB.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2019.10a
• /
• pp.201-203
• /
• 2019

5G 시스템은 혁신적인 발전을 거듭하며 강력해진 기술 표준을 근간으로 초광대역 이동형 데이터 서비스, 대규모 사물통신 서비스 등을 제공하고 있다. 본 논문에서는 SW를 기반으로 한 5G의 기술 개발 방법론을 제안한다. 또, 실제 환경에서 차세대 모바일 네트워크의 성능 분석이 가능한 SW 기반의 시스템 레벨 테스트베드 및 모니터링 프로그램을 OAI(Openairinterface) 5G 연구 단체의 오픈소스를 이용하여 구현한다. 기존 하드웨어 위주의 단일 칩 시스템(SoC)을 이용한 구현은 손상되기가 쉽고 유지보수가 힘들다는 단점이 있다. 하지만 기존 하드웨어 칩을 소프트웨어 기반인 소스코드로 구현하면 유지 보수가 용이하다는 장점뿐만 아니라 하드웨어가 변경되더라도 다른 하드웨어에 호환되는 이식성 때문에 생산성이 높아지며 비용 절감의 효과도 기대할 수 있다.

• Information and Communications Magazine
• /
• v.31 no.11
• /
• pp.73-78
• /
• 2014

본고에서는 현재 급증하고 있는 모바일 트래픽을 수용하기 위하여 제안된 LTE-U기술의 개념 및 특성, 요구사항 등을 살펴보고자 한다. 비면허 대역을 이용한 LTE-U 혹은 LTE-LAA 기술은 WiFi와 동일한 주파수 대역을 이용하기 때문에 두 방식간의 공존문제가 중요하게 다루어져야 한다. 또한 주파수 정책과 기술의 밀접한 관련성을 고려하여 다양한 LTE-U 기술 채용 시나리오와 후보 주파수 대역을 비교, 분석하여 5G 이동통신시스템 개발 및 연구에 있어서 비면허 대역을 이용한 기술 관련한 현황 및 시사점을 도출해보고자 한다.

• Proceedings of the KAIS Fall Conference
• /
• 2009.05a
• /
• pp.487-490
• /
• 2009

ELP 계열 음성부호화기는 4.8kbps 내외의 전송률에서 양호한 음질을 얻을수 있으며 ITU-T, TIA/EIA 등 여러 국제 표준화 기구를 통해 다양한 응용분야에서 표준화가 이루어졌다. 이중에서 G.723.1은 멀티미디어 통신 환경하의 음성 전송 표준 보코더로 개발되었으며 G.723.1은 5.3kbps/6.3kbps의 이중 전송률을 갖는 구조로 현재 별정 통신으로 상용화되는 인터넷폰과 그 외의 이동 통신용 보코더로 사용되고 있다. G.723.1에서 사용되는 LSP 파라미터는 일정한 스펙트럼 민감도와 낮은 스펙트럼 왜곡을 보인다. 본 논문에서 제안하는 알고리즘은 음성신호의 에너지가 대개 낮은 주파수에 분포한다는 특징을 이용하여 대역폭을 가변으로 조정하였다. 실험결과, 부호화기 전체 계산시간은 약 6%의 감소하였다.