• KIPS Transactions on Computer and Communication Systems
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• v.3 no.1
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• pp.7-14
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• 2014

The rapid increase of mobile devices such as smart phone and smart pad have raised the needs for seamless multimedia services during moving at anytime and anywhere. Current 4G mobile devices are equipped with both 4G (LTE) and WLAN (WiFi) interfaces, and mobile services operators provide wireless Internet services using 4G network with a wider coverage and WiFi zone. Generally users prefer to use the Internet services through WLAN rather than LTE in the coverage of WLAN. However, since WLAN has a long L2 handover latency, it is difficult to support seamless services during a handover. In this paper, we proposed an efficient handover scheme based on flow mobility for WLANs to support a seamless service during handovers by using the overlaid 4G network with a wider coverage. Also, we showed the outperformance of the proposed scheme on a testbed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.8
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• pp.965-973
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• 2016

As increase of IoT services in wireless communications, the performance evaluation is required to connects massive number of devices in LTE-A system. Existing performance analysis of 3GPP TR 37.868 is shown the limited results up to the number of devices only 30,000 in a cell. So, it is required the performance analysis according to various parameter values in the greater number of devices environment. In this paper, to evaluate the performance, we developed the new modules to simulate LTE-A random access procedures because of a limit that accommodate massive number of devices in existing LTE module. The simulator was developed by OPNET and it can support up to 100,000 devices per cell. This paper also represents the performance analysis results according to the number of preambles, the maximum number of preamble transmissions, backoff indicator and msg2 window size in the same environment with 3GPP TR 37.868. This results are expected to be utilized such as the transition to 5G network and standardization activities.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.10
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• pp.1879-1888
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• 2015

This paper evaluates the adjacent channel coexistence issues between LAA(License Assisted Access) system and other system (e.g. Wi-Fi) system in 5 GHz unlicensed spectrum. LAA is a technology to achieve enhanced data rate by aggregating licensed and unlicensed spectrum using CA(Carrier Aggregation). The coexistence study is essential before deploying LTE in unlicensed spectrum to verify the impact of LTE on the existing system such as Wi-Fi including system in throughput and regulatory aspects. This paper evaluates and analyzes the RF requirements of LTE system using interference analysis of coexistence study when operating at adjacent frequency channel of the Wi-Fi system in order to minimize the impact of LTE system into Wi-Fi system.

• Electronics and Telecommunications Trends
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• v.25 no.6
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• pp.144-156
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• 2010

기존 2G/3G 무선 네트워크에서 많은 네트워크 요소들과 관련된 파라미터들이 수동으로 설정되었다. 네트워크 구성 요소들과 이와 관련된 파라미터들의 설계, 설정, 통합 및 관리 기능은 효율적이고 신뢰성 있는 네트워크 운용을 위하여 매우 중요하다. 그러나, 이들 네트워크 파라미터 조정에는 전문적인 엔지니어의 수작업이 필요하다. 이러한 수작업 과정은 시간이 많이 걸리고 잠재적으로 수작업에 따른 오류 발생 가능성이 있다. 이동 통신 시스템에서 펨토셀 및 차세대 4G 도입이 가시화됨에 따라, 기지국의 설치 및 운용 과정에서 Self-Configuration, Self-Optimization 및 Self-Healing과 같은 자동화 기능을 포함하는 SON 기술에 대한 관심이 높아지고 있다. 본 고에서는 LTE에서의 SON 기술 관련 주요 기술적 내용을 정리하고, 표준화 동향 및 업체 기술 동향에 대하여 살펴보고자 한다.

• The Journal of Society for e-Business Studies
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• v.16 no.3
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• pp.145-158
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• 2011

Recently, the rapidly increased use of smartphone devices provides both opportunity and problems at the same time to the telecom companies in domestic and world wide. It provides a great opportunity to overcome the market stagnation of the existing voice- centric communications, and also problems of building a highly efficient new wireless access networks to accommodate huge volume of data traffic among smart devices. Facing with the age of keen competition, telecom companies have two kinds of strategies for network transition; a strategy of building uniform LTE -based 4G networks as fast as possible, and a hybrid network enhancement strategy compounding 3G and 4G networks using HSP A+, WiFi, cloud computing, etc. It is difficult to predict which strategy will have more successful outcome in the near future. This paper studies the trends and issues of network enhancement policies and transition strategies to the 4G network era, and tries to draw appropriate and efficient ways for network enhancement and operation.

• Journal of IKEEE
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• v.24 no.1
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• pp.90-96
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• 2020

As various communication services have emerged due to the development of mobile communication technology, there is a need for a wideband antenna supporting multiple communication services with one antenna. In this paper, we propose a planar slot wideband antenna that can support all the communication services of 3.1~4.99GHz, the low frequency band of 5G, in addition to the existing communication services such as WiFi, LTE 2300/2500, and WiMAX. Through the simulation, the optimized antenna design parameters were obtained, and the antenna was fabricated to implement an antenna with a frequency bandwidth of 1.96~6.01GHz (S11 <-10dB) and presented the radiation pattern and gain of the antenna. The proposed antenna is a multi-band antenna that can provide all the services of LTE, Wifi, WiMAX, and 5G low frequency bands. It can be used as a repeater antenna in radio shadow area such as buildings, dense areas, and ships.

• Information and Communications Magazine
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• v.24 no.3
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• pp.97-111
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• 2007

전 세계적으로 2세대 및 3세대 무선이동통신 서비스의 성공적인 상용화에 힘입어 현재 3.5세대 이동통신시스템의 상용화 단계까지 이르렀다. 한걸음 더 나아가 3GPP/3GPP2에서는 MT-2000 고도화시스템에 대한 표준화 작업이 활발히 진행되고 있다. 각 표준화 기구에서 제시한 향후 표준화 일정 및 현재의 기술개발 추세로 미루어 볼 때 수년 내에 무선통신시스템의 새로운 장이 펼쳐질 것으로 기대된다. 특히 3GPP에서는 기존 3G-WCDMA 무선접속기술 대신에 하향 OFDMA 및 상향 SC-FDMA 무선접속기술을 이용하는 E-UTRA/UTRAN 시스템의 표준화 작업을 진행하고 있다. 특히 이 표준화 작업에 전 세계 운영회사, 제조사, 표준화 기구 및 관련종사자들의 관심이 어느 때보다 높기 때문에 표준 기술의 논의 및 검증이 더 활발히 진행되고 있으며 이는 표준기술 완성도를 높여 향후 발간될 LTE 시스템의 경쟁력 제고에 크게 이바지 할 것으로 예상된다. 현재 LTE 표준화 작업은 3단계로 나누어 진행되어 왔으며 2006년 3월 현재 마지막 세 번째 단계를 막 시작하는 시기에 있다. 이에 즈음하여 본기고문에서는 LTE 표준기술의 이해를 돕고 및 향후 표준화에 대한 향방을 가늠하는데 일부 도움을 제공하기 위해 현재까지 진행된 물리계층 표준기술 및 향후 해결해야할 문제들에 대해서 개념위주로 기술하였다. 기고문은 LTE 시스템 요구사항 및 향후 일정을 서론부에 제시하고 이어 E-UTRAN 프로토콜 구조, 상 하향 무선접속 기술, 물리계층 기술표준 현황, 그리고 마지막으로 맺음말의 순으로 구성되어 있다.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.1
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• pp.49-54
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• 2010

3GPP(Third Generation Partnership Project) LTE system that is the next step forward in cellular 3G services address the issues related to power saving at LTE base station. This is because that most of the energy in a typical telecommunication network is consumed by the wireless network's base station site. Power saving at LTE base station fall in with low-carbon green technology. This thesis proposes a power saving MAC protocol for LTE base station which utilizes different graded DRX/DTX(Discontinuous. Reception/Transmission). Considering traffic type in UE, proposed MAC protocol controls adaptive DRX/DTX cycle. The proposed method is more improve power saving performance than another method which is unchanged DRX/DTX by conditions. In this thesis, I propose an power saving MAC protocol in an environment where LTE base station are communicated with UE and prove improvement in performance through simulations.

• Information and Communications Magazine
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• v.23 no.6
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• pp.29-38
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• 2006

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.6
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• pp.1-16
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• 2013

Smartphones and tablets including phone, calendar are the necessities of modern man. They are one of the MN(Mobile Node), each with wireless network capabilities. Necessities of modern human MNs are almost included cellular module available in LTE/3G and Wi-Fi module for high-speed Internet. Until now, MN mobility management is handled, but using network-based mobility management in this paper. Then, carriers can manage and maintain the network for low-cost. In addition, it was considered that use a lot of modern people with Wi-Fi and LTE/3G, and using Cross-Layer-Based handoff.