• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.4
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• pp.18-25
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• 2012

As the demand for smart phone user is rapidly increasing in recent years, the development of new mobile communication system which provides more improved quality compared to existing 3G standard is highly requested. In this point, the long-term evolution (LTE) system, which was being developed in mid of 2000's, has attracted a considerable attention. The LTE has been developed continuously to result a release 10 which is called as LTE-Advanced (LTE-A) in 2010. Among various features in LTE-A, the multiuser MIMO (MU-MIMO) design is expected to give better quality for throughput, spectral efficiency, and latency. In this paper, we first review the development process from LTE to LTE-A. We also provide the overview of design challenges and specific solutions for MU-MIMO systems developed in LTE-Advanced standard.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.4
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• pp.451-455
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• 2014

In LTE (Long Term Evolution)/LTE-A (Long Term Evolution-Advanced) networks, hierarchical macro/femto-cell structure is adopted to enhance system capacity. Such a femto-cell is deployed as a Closed Subscriber Group (CSG) eNB. However, the inbound handover to CSG cell experiences longer delay than normal handover because it spends more time detecting the associated CSG cells due to its sparse deployment. Most of all the legacy UEs (User Equipments) have been implemented without considering the inbound CSG handover. Accordingly, they may not meet the performance requirements on the cell discovery described in the LTE/LTE-A standards. Therefore, in this paper, the performance of the CSG femto-cell detection is evaluated using computer simulation. The evaluation results will provide a basis to tackle the latency problem of inbound CSG handover.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.8
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• pp.712-723
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• 2013

Recent exploration of smart-phone user is fueling the deployment of long term evolution (LTE) service that offers higher data rates service over 3G HSPA networks. In particular, Korea, mobile powerhouse, recently launched the service of LTE-Advanced (LTE-A) which is the latest release in LTE standard. Multiple-input-multiple-output (MIMO) technology is the one of key enablers for LTE and LTE-A for achieving high data rate. MIMO technology has received much attention since it is possible to achieve channel capacity in proportion to the number of antennas without increasing frequency and power. In this paper, we overview of the theoretical background of MIMO technology regarding from single-user MIMO, multiuser MIMO, and massive MIMO and design considerations to implement the communication system.

• Journal of the Korean Society for Railway
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• v.20 no.1
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• pp.20-30
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• 2017

Due to the evolution of wireless communications technology, Long Term Evolution (LTE), which is a $4^{th}$ generation mobile communications system, has been adopted as a railway communications system. This LTE Railway (LTE-R) system is composed of various elemental functions, which are largely categorized into public safety and wireless communications for train control. Research on the public safety functions of railway communications have their roots in TRS based national public safety communication systems, and research on wireless communications functions for train control have their roots GSM-R, which is utilized by the ETCS in Europe. Based on these circumstances, this paper first analyzes the requirements for developing public safety technology in LTE-R, and compares those requirements with the functions of public safety LTE (PS-LTE), which is being deployed for the first time in the world by the South Korean government. Based on an analysis of the common and specific functions of LTE-R and PS-LTE, we conclude that there is little problem in integrating LTE-R and PS-LTE from the perspective of functionality. Second, this paper provides a comparison of the LTE-R requirements for the Quality of Service (QoS) with those of GSM-R utilized by the ETCS. This offers a guideline to allow LTE-R to be applied to a 500km/h train control system.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.5
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• pp.45-55
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• 2010

While Long Term Evolution-Frequency Division Duplexing (LTE-FDD) is regarded as one of the strong candidates for "4G" wireless broadband access in FDD field, LTE-Time Division Duplexing (TDD) is emerging as one possible migration path for WiMAX-TDD in some cases as well as the migration path for Time Division-Synchronous Code Division Multiple Access (TD-SCDMA). In this paper, we analyze the feasibility of dual mode with LTE-TDD in two combinations: dual mode LTE-FDD/TDD and dual mode Worldwide Interoperability for Microwave Access (WiMAX)-TDD/LTE-TDD. Thanks to the commonality in numerology, terminology, and frame structure between LTE-FDD and LTE-TDD, dual mode LTE-FDD/TDD looks feasible in a cost-effective manner. Thanks to the commonality in scheduling algorithm, control mechanism, and supported spectrum bands, it is shown that dual mode WiMAX-TDD/LTE-TDD looks feasible as well. It should be also noted that the commonality in numerology and frame structure is critical for building a chip while the commonality in algorithms and control mechanisms is critical to make it work.

• Journal of Advanced Navigation Technology
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• v.24 no.2
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• pp.115-120
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• 2020

PS-LTE, which is mentioned as a next-generation disaster network technology, is a communication technology that supports communication between terminals and group communication necessary for public safety communication based on LTE technology. Currently, Korea is establishing a PS-LTE network construction plan and installing a PS-LTE system. The world is currently making a lot of efforts to build a disaster network system using PS-LTE. However, due to the characteristics of the closed network that only the related persons can access, it can not be operated like the existing commercial network, so it is necessary to build a new network. And it is expected that many periods and costs will be required. In order to establish a disaster safety communication network efficiently, it is necessary to consider the linkage of PS-LTE network, which is newly constructed by complementing the problems such as security and access priority to existing LTE network rather than unconditional new construction.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.11
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• pp.2405-2410
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• 2012

The 4th generation mobile communication system, LTE, does not support an additional core network to provide voice service, and it is merged into a packet network based on all IP. Although Voice service over LTE can be supported by VoIP, it will be provided by the existing 3G networks because of the discontinuity of LTE coverage. However, it is inevitable to adopt VoIP over LTE to provide high quality voice service. In this paper, we investigate the capacity of VoIP over LTE. Our results indicate that spectral efficiency can be significantly improved as channel bandwidth increases in terms of VoLTE capacity. In addition, we can achieve higher VoLTE capacity without decreasing control channel capacity.

• Journal of Digital Contents Society
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• v.14 no.3
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• pp.291-301
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• 2013

This study is to derive the factors that influence the acceptance of LTE smart phones. Using an extended technology acceptance model to look at the factors affecting the acceptance LTE smart phone. Variables and the LTE features on the personal characteristics variables were chosen based on the study. This study was done through a survey. Surveyed LTE smart phone's primary audience, taking into account the age of 20 were analyzed mainly. LTE smart phone's acceptance factors affecting individual innovation, speed, price factors. When formulating marketing strategies in the future, based on the results of this study, elements that can stimulate innovation and speed, not just an individual's stability, if we estimate that we can derive a more meaningful and effective marketing results.

• Journal of Satellite, Information and Communications
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• v.12 no.2
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• pp.15-20
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• 2017

A conventional TV relay broadcast is a method of transmitting a program by means of a microwave, a leased wire, or a satellite. With the latest advances in LTE network, a relay approach using LTE mobile communications network has become increasingly competing with the traditional TV relay broadcast method. Since 2012, TV Chosun has been using the LTE network for marathon production, and channel A has also broadcast a marathon production broadcast using the LTE network. Therefore in this paper, we investigated the marathon relay method using LTE mobile communications network and compared with the traditional TV marathon relay method, and then suggested the optimum method for the marathon relay.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.4
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• pp.9-16
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• 2013

Long term evolution (LTE) and LTE-Advanced (LTE-A) systems adopt closed-loop multiple-input multiple-output antenna techniques. Equal gain transmission which has equal gain property is the key factor in their codebook design. In this paper, a novel differential codebook structure which maintains the codebook design requirements of LTE or LTE-A systems. Especially, eight-phase shift keying (8-PSK) constellations are used as elements of codewords, which not only maintain equal gain property but also reduce the computation complexity of precoding and decoding function blocks. The equal gain property is very important to uplink because the performance of uplink is very sensitive to the peak-to-average power ratio (PAPR). Moreover, the operation of the proposed differential codebook is explained as a rotation-lock structure. As the results of computer simulations, the steady-state throughput performance of the proposed codebook shows at least 0.9dB of SNR better than those of the conventional LTE codebook with the same amount of feedback information.