• Title, Summary, Keyword: LTE

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Dual Bias Modulator for Envelope Tracking and Average Power Tracking Modes for CMOS Power Amplifier

  • Ham, Junghyun;Jung, Haeryun;Bae, Jongsuk;Lim, Wonseob;Hwang, Keum Cheol;Lee, Kang-Yoon;Park, Cheon-Seok;Yang, Youngoo
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.14 no.6
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    • pp.802-809
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    • 2014
  • This paper presents a dual-mode bias modulator (BM) for complementary metal oxide semiconductor (CMOS) power amplifiers (PAs). The BM includes a hybrid buck converter and a normal buck converter for an envelope tracking (ET) mode for high output power and for an average power tracking (APT) mode for low output power, respectively. The dual-mode BM and CMOS PA are designed using a $0.18-{\mu}m$ CMOS process for the 1.75 GHz band. For the 16-QAM LTE signal with a peak-to-average power ratio of 7.3 dB and a bandwidth of 5 MHz, the PA with the ET mode exhibited a poweradded efficiency (PAE) of 39.2%, an EVM of 4.8%, a gain of 19.0 dB, and an adjacent channel leakage power ratio of -30 dBc at an average output power of 22 dBm, while the stand-alone PA has a PAE of 8% lower at the same condition. The PA with APT mode has a PAE of 21.3%, which is an improvement of 13.4% from that of the stand-alone PA at an output power of 13 dBm.

Radio Resource Management of CoMP System in HetNet under Power and Backhaul Constraints

  • Yu, Jia;Wu, Shaohua;Lin, Xiaodong;Zhang, Qinyu
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.8 no.11
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    • pp.3876-3895
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    • 2014
  • Recently, Heterogeneous Network (HetNet) with Coordinated Multi-Point (CoMP) scheme is introduced into Long Term Evolution-Advanced (LTE-A) systems to improve digital services for User Equipments (UEs), especially for cell-edge UEs. However, Radio Resource Management (RRM), including Resource Block (RB) scheduling and Power Allocation (PA), in this scenario becomes challenging, due to the intercell cooperation. In this paper, we investigate the RRM problem for downlink transmission of HetNet system with Joint Processing (JP) CoMP (both joint transmission and dynamic cell selection schemes), aiming at maximizing weighted sum data rate under the constraints of both transmission power and backhaul capacity. First, joint RB scheduling and PA problem is formulated as a constrained Mixed Integer Programming (MIP) which is NP-hard. To simplify the formulation problem, we decompose it into two problems of RB scheduling and PA. For RB scheduling, we propose an algorithm with less computational complexity to achieve a suboptimal solution. Then, according to the obtained scheduling results, we present an iterative Karush-Kuhn-Tucker (KKT) method to solve the PA problem. Extensive simulations are conducted to verify the effectiveness and efficiency of the proposed algorithms. Two kinds of JP CoMP schemes are compared with a non-CoMP greedy scheme (max capacity scheme). Simulation results prove that the CoMP schemes with the proposed RRM algorithms dramatically enhance data rate of cell-edge UEs, thereby improving UEs' fairness of data rate. Also, it is shown that the proposed PA algorithms can decrease power consumption of transmission antennas without loss of transmission performance.

Building More Secure Femtocell with Improved Proxy Signature (개선된 위임 서명 방식을 이용해서 더 안전한 펨토셀 환경 구축)

  • Choi, Hyoung-Kee;Han, Chan-Kyu;Kim, Seung-Ryong
    • Journal of the Korea Institute of Information Security & Cryptology
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    • v.24 no.1
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    • pp.75-86
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    • 2014
  • Demand for the femtocell is largely credited to the surge in a more always best connected communication conscious public. 3GPP defines new architecture and security requirement for Release 9 to deal with femtocell, Home eNode B referred as HeNB. In this paper, we analyze the HeNB security with respect to mutual authentication, access control, and secure key agreement. Our analysis pointed out that a number of security vulnerabilities have still not been addressed and solved by 3GPP technical specification. These include eavesdropping, man-in-the-middle attack, compromising subscriber access list, and masquerading as valid HeNB. To the best of our knowledge, any related research studying HeNB security was not published before. Towards this end, this paper proposes an improved authentication and key agreement mechanism for HeNB which adopts proxy-signature and proxy-signed proxy-signature. Through our elaborate analysis, we conclude that the proposed not only prevents the various security threats but also accomplishes minimum distance from use-tolerable authentication delay.

Proposal Scheme of a D2D Communication in Smart Shipyard (스마트 조선소내 D2D 통신 기술 적용 방안 제안)

  • Kim, Su-Hyun;Lee, Seong Ro;Min, Sang-Won
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.39C no.12
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    • pp.1261-1266
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    • 2014
  • Smart shipyard, all of the business of shipyard by using a mobile application, and the rapid spread of smart equipment, the overload of infrastructure due to a variety of mobile services is expected. Because macrocell and femtecell to reduce the overloading of existing infrastructure, additional core network devices have a problem, in this paper, the efficiency of resources than the communication over the existing infrastructure smart shipyard network to improve, to apply the D2D communication technology that can reduce the load on the infrastructure. The proposed routing path plan in accordance with the transfer method and the traffic type of network configuration and D2D equipment navigation and data for applying a smart shipyard. Whether to execute the function to overload traffic in the core network can send to the optimized path was confirmed by using the state transition diagram. Smart shipyard, by applying D2D communication allow efficient traffic handling than conventional communication method.

A study on the characteristics of multi load transfer ground anchor system (다중정착 지반앵커의 하중전달 특성에 관한 연구)

  • Kim, Ji-Ho;Jeong, Hyeon-Sic;Kwon, Oh-Yeob;Shin, Jong-Ho
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.16 no.1
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    • pp.25-50
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    • 2014
  • In order to identify a load transfer mechanism of ground anchors, the behavior of multi load transfer ground anchor systems was investigated and compared with those of compression type anchors and tension type anchors. Large scale model tests were performed and stress-strain relationships were obtained. The load transfer mechanism of ground anchors was also investigated in the field tests. Finally, numerical analyses to predict the load-displacement relationships of anchors were conducted. It is concluded that the load transfer characteristics of MLT anchors are mechanically much more superior in the pull-out resistance effect than those of existing compression and tension type anchors. From the results of research work, we could suggest that the max pull-out capacity of anchor capacity to each the soil condition. Also, the MLT anchors can be used to achieve both structural enhancement and economic construction in earth retaining or supporting structures.

Ultra Wide Area Wireless Backhaul Network System Based on Large Scale Array Antenna (대형 어레이 안테나 기반 초광역 무선 백홀망 시스템)

  • Go, SeongWon;Kim, Hyoji;Lee, Ju Yong;Cho, Dong-Ho
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.40 no.7
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    • pp.1354-1362
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    • 2015
  • Heterogeneous network technology is expected to be a core technology for 5G mobile communications. 5G mobile network would be composed of many base stations even have mobility, then the operator should connect base stations through the wireless backhaul technology. This paper presents Ultra Wide Area Wireless Backhaul Network System with massive array antenna. We conducted link budget analysis for Ultra Wide Area Wireless Backhaul Network and performance analysis of massive array antenna system through the transmission simulator based on beamforming technology. In wide area ($10km^2$) wireless backhaul system composed of massive antenna, we achieved 5 bps/Hz average spectral efficiency with 1 W transmission power per beam.

Toward Mobile Cloud Computing-Cloudlet for implementing Mobile APP based android platform (안드로이드 기반의 모바일 APP 개발을 위한 모바일 클라우드 컴퓨팅)

  • Nkenyereye, Lionel;Jang, Jong-Wook
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.19 no.6
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    • pp.1449-1454
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    • 2015
  • Virtualization lacks capabilities for enabling the application to scale efficiently because of new applications components which are raised to be configured on demand. In this paper, we propose an architecture that affords mobile app based on nomadic smartphone using not only mobile cloud computing-cloudlet architecture but also a dedicated platform that relies on using virtual private mobile networks to provide reliable connectivity through LTE(Long Term Evolution) wireless communication. The design architecture lies with how the cloudlet host discovers service and sends out the cloudlet IP and port while locating the user mobile device. We demonstrate the effectiveness of the proposed architecture by implementing an android application responsible of real time analysis by using a vehicle to applications smartphone interface approach that considers the smartphone to act as a remote users which passes driver inputs and delivers outputs from external applications.

Performance Analysis of a Dense Device to Device Network

  • Kim, Seung-Yeon;Lim, Chi-Hun;Cho, Choong-Ho
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.8 no.9
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    • pp.2967-2981
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    • 2014
  • Device-to-Device (D2D) communication is a technology component for long-term evolution-advanced (LTE-A). In D2D communication, users in close proximity to each other can communicate directly without going through a base station; such direct communication can improve spectral efficiency. Although D2D communication brings improvement in spectral efficiency, it also causes interference to the cellular network as a result of spectrum sharing. In particularly, D2D communication can generate interference for each D2D pair when the common wireless medium in a co-located limited area is accessed. Even though the interference management for between the D2D pair and cellular networks has been proposed, the interference reducing methods have still not been fully studied for the D2D pairs. In this paper, we investigate the problem of D2D pair coexistence in which interference is considered between D2D pairs. Using a signal to interference model for a target D2D pair, we provide an analysis of the aggregated throughput of a dense D2D network. For a target D2D pair, we assume that the desired signal and interference signals obey multipath fading and shadow fading. Through analysis, we demonstrate the effect of cluster size such as the number of D2D pairs and the size of the considered area on the network performance. The analytical results are compared with computer simulations. Our work can be used for a rough guideline for controlling the system throughput in a dense D2D network environment.

Limit Analysis of the Distance between DU and RU in 4G FDD Mobile Communication Systems (FDD 방식의 4G 이동통신 기지국에서 DU와 RU간 한계거리 분석)

  • Kim, Sung-Man
    • The Journal of the Korea institute of electronic communication sciences
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    • v.7 no.1
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    • pp.135-139
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    • 2012
  • A majority of 4G Mobile communication manufacturers have launched separated-type base stations composed of DU (digital unit) and RU (ratio unit). DUs are usually installed in the central office, while RUs with antennas are installed on the top of building or pole. Therefore, the allowable distance between DU and RU is very important for cell planning. In this paper, we analyze the allowable distance between DU and RU induced by closed-loop MIMO (mulitple input multiple output) technology in 4G FDD (frequency division duplexing) mobile communication systems. In conclusion, the distance limit between DU and RU is dependent on the frequency of the wireless communication, and the allowable distance is about 11 km when assuming the operating frequency is 2 GHz.

Estimation of GPS Holdover Performance with Ladder Algorithm Used for an UFIR Filter (UFIR 필터 Ladder 알고리즘 이용 GPS Holdover 성능 추정)

  • Lee, Young-kyu;Yang, Sung-hoon;Lee, Chang-bok;Heo, Moon-beom
    • Journal of Institute of Control, Robotics and Systems
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    • v.21 no.7
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    • pp.669-676
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    • 2015
  • In this paper, we described the simulation results of the phase offset performance of a clock in holdover mode which was normally operated in GPS Disciplined Oscillator (GPSDO). In the TIE model, we included the time error term caused by environmental temperature variation because one of the most important parameters of clock phase error is the frequency offset and drift caused by the variation of temperature. For the simulation, we employed Maximum Time Interval Error (MTIE) for the performance evaluation when the frequency offset and drift are estimated by using an Unbiased Finite Impulse Response (UFIR) filter with ladder algorithm. We assumed that the noise in the GPS measurement is white Gaussian with zero mean and 1 ns standard deviation, and temperature linearly varies with a slope of $1{^{\circ}C}$ per hour. From the simulation results, the followings were observed. First, with the estimation error of temperature of less than 3 % and the temperature compensation period of less than 900 seconds, the requirement of CDMA2000 phase synchronization under 10 us could be achieved for more than 40,000 seconds holdover time if we employ an OCXO (Oven Controlled Crystal Oscillator) clock. Second, in order to achieve the requirement of LTE-TDD under 1.5 us for more than 10,000 seconds holdover time, below 3 % estimation error and 500 seconds should be retained if a Rubidium clock is adopted.