• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.6A
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• pp.458-467
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• 2009

Long Tenn Evolution (LTE) is the next generation mobile phone technology which has being standardized by the Third Generation Partnership Project (3GPP). In the existing mobile communication networks, voice traffic is delivered through circuit switched networks. In LTE, however, all kinds of traffic are transferred through IP based packet switched networks which has best-effort characteristic. Therefore, providing QoS in LTE system is difficult. In order to provide QoS in LTE, RRM is very important. Especially, in part of RRM, call admission control (CAC) performs an important function to reduce network congestion and guarantee a certain level of QoS for on-going calls. In this paper, we propose a CAC algorithm in order to provide QoS for various kinds of services in LTE system. The performance of the proposed algorithm is evaluated with various simulation environments. The results show that the proposed algorithm provides QoS through rejections of requested calls. Especially, the proposed CAC algorithm can be satisfied with packet delay requirement defined in LTE specification.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.2
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• pp.127-134
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• 2017

In this paper, we try to solve the frequency shortage due to the increase of LTE terminals and the traffic jam caused by the inefficient WiFi connection method. The proposed LTE-WIFI Vertical Handover method uses a pre-authentication method of the AP through LTE and a method of controlling the access AP of the terminal using the RADIUS server. Through the simulation, the proposed method shows that the access speed of the AP is improved by about 95% compared to the conventional connection method, and the connection speed is improved by about 18% compared to the conventional method. Providing seamless AP through pre-authentication system and improving wireless network speed through AP access distribution can solve LTE frequency shortage problem and improve wireless network usage satisfaction.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.827-829
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• 2015

This paper presents process of the UE obtains the cell system information in order to achieve communication with the LTE network on the LTE. This paper deals with the process of extracting MIB(Master Information Block) cell system information in LTE. To study the 3GPP LTE standard spec series 36.200 and 36.300, the simulation is implemented to extract the MIB in MATLAB program. The simulation process is divided into three parts. It consisted of a part that extracts the PSS, SSS and MIB. Called a cell search process for detecting the PSS and SSS, the process is to be done in order to extract only the cell system information. The simulation program is verified based on the signal captured from the real Air.

• Journal of Navigation and Port Research
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• v.46 no.6
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• pp.576-584
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• 2022

AIS is widely utilized in vessel traffic services for marine traffic safety. In 2021, Korea deployed the high-speed maritime wireless communication system (LTE-Maritime) on the sea following IMO's proposal for the introduction of e-Navigation. In this paper, vessel trajectory data from AIS and LTE-Maritime were used for vessel trajectory prediction to compare and analyze the two systems. The results show that the trajectory prediction error of LTE-Maritime was smaller than that of AIS due to the granular and uniform data provided by LTE-Maritime. Additionally, it was revealed that time interval is the most important factor influencing the errors in trajectory prediction, with the prediction error of LTE-Maritime growing at a slower rate of 17% than AIS. This research contributes to the literature by quantitatively comparing AIS and LTE-Maritime systems for the first time.

• Information and Communications Magazine
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• v.33 no.4
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• pp.86-91
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• 2016

커버리지를 확대하고 다이버시티 이득의 극대화를 통해 전송 신뢰도를 높이는데 효과적인 무선 중계기술은 많은 연구자의 높은 관심을 받아왔으며 그동안의 주요 연구결과를 바탕으로 3GPP Release 10에 LTE/LTE-A를 위한 중계기술로 표준화되기에 이르렀다. 본고에서는 LTE/LTE-A를 위한 중계기술이 표준기술로 포함된 Release 10을 중심으로 중계 시스템의 전반적인 구조를 소개하고 중계 절차 및 주요 네트워크 프로토콜을 살펴본다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.4
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• pp.805-814
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• 2013

According to the shut-down of Analog TV service on 30th. December, 2012, UHF Digital Dividend Band (698~806MHz) could be used for Mobile service such as LTE(Long Term Evolution). In the condition that this band is allocated for LTE service, Interference evaluation between LTE and adjacent DTV service was carried out, using LTE-A system-level simulator which was developed for simulation of IMT-Advanced technology. If LTE service be commercialized in this band, this study proposes the coexistence condition through the interference evaluation such as the effects not only to DTV receiver from LTE terminal but also to LTE base station from DTV transmitter. It is expected that the coexistence condition by these studies will be applied to network algorism for IMT-Advanced system in this band.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.1
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• pp.24-31
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• 2015

A differential codebook using M-ary phase shift keying (M-PSK) constellation as its codeword elements, is proposed for Long term evolution (LTE), LTE-Advanced (LTE-A), and/or WiMAX systems. Due to the temporal correlation of the adjacent channel, the consecutive precoding matrices are likely to be similar. This approach quantize only the differential information of the channel instead of the whole channel subspace, which virtually increase the codebook size to realize more accurate quantization of the channel. Especially, the proposed codebook has the same properties of LTE release-8 codebook that is, constant modulus, complexity reduction, and nested property. The mobile station can be designed by using a less expensive non-linear amplifier utilizing the constant modulus property. Computer simulations show that the capacity of the proposed codebook performs better than LTE release-8 codebook with the same amount of feedback information.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.12
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• pp.1365-1372
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• 2014

In recent, the LTE(Long-Term Evolution) mobile communication system has been commercialized and a variety of service is being provided. Comparing to the old wireless access systems such as 3G mobile communications, in particular, the LTE system supports a service requiring a high transmission rate by providing broadband wireless access. In order to understand the possibility of successful support of a multimedia service such as IPTV(Internet Protocol Television) through the LTE system, it is necessary to understand the mechanism that decides the transmission rate supported by the LTE system. This paper, therefore, discusses on the relationship between a number of metrics such as CQI and BLER that affects the transmission rate with the measurement results from the field tests.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.12
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• pp.1045-1053
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• 2013

In this paper, we propose a new power-saving mechanism (PSM) for Long-Term Evolution (LTE) systems by considering a round-trip delay between a user equipment (UE) and its correspondence node. The proposed PSM changes the order of the operational procedures of the legacy LTE PSM by taking the traffic arrival pattern suffering the round-trip delay into account. After modeling the round-trip delay, we numerically analyze the proposed PSM with respect to energy consumption and buffering delay. Then, we characterize these performances by employing a simple energy-delay tradeoff (EDT) curve according to the operational parameters. The resulting EDT curve clearly shows that the proposed PSM outperforms the legacy LTE PSM in terms of both the energy consumption and buffering delay.

• Journal of Advanced Navigation Technology
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• v.16 no.2
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• pp.219-226
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• 2012

Since OFDM(Orthogonal Frequency Division Multiplexing) technology is applied into LTE(Long Term Evolution)/LTE-Advanced system, it is important to estimate the spectrum sharing and to analyze interference in LTE system based on the characteristics of frequency assignment. Therefore, in this paper, a study on the adjacent channel interference between two operators/systems to provide LTE services. For co-existence of LTE systems, the relative capacity loss and the relative throughput loss in uplink and downlink have been simulated to evaluated ACIR(Adjacent Channel Interference Ratio) values with 5% loss rate. Some parameters such as the location of user, aggressor bandwidth, and the separation offset affect the required ACIR value for spectrum sharing, and these results and interference analysis schemes in this article can provide reliable reference for LTE RF standardization and efficient frequency utilization in future.