• 한국전자파학회논문지
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• 제21권4호
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• pp.381-391
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• 2010

본 논문에서는 상용 초고주파 MEMS 스위치를 이용하여 세 개의 주파수 대역에서 재구성 동작이 가능한 주파수 재구성 능동 배열 안테나 시스템(Reconfigurable Active Array Antenna System: RAA System)을 제안하였다. MEMS 스위치는 삽입 손실 및 선형성 특성이 우수하고 격리도가 높아 주파수 재구성 시스템 구현 시, 재구성을 위한 스위치로 인한 성능 열화가 거의 없다는 장점이 있다. 제안된 주파수 재구성 능동 배열 안테나 시스템은 간단한 구조의 임피던스 매칭 회로(Reconfigurable impedance Matching Circuit: RMC)를 갖는 주파수 재구성 증폭기(Reconfigurable Front-end Amplifier: RFA)가 집적화 되어 있으며, 안테나 방사체(Reconfigurable Antenna Element: RAE)와 재구성 제어 보드(Reconfiguration Control Board: RCB)로 구성되어 있다. 본 논문에서 제안한 RAA 시스템은 850 MHz, 1.9 GHz, 3.4 GHz의 세 개 주파수로 재구성되어 동작하며, 안테나 방사체는 $2{\times}2$ 배열을 가지고 각각의 방사체는 광대역 다이폴 형태를 갖는다. 제작된 RAA 시스템은 실험을 통하여 그 타당성을 확인하였다.

• 디지털산업정보학회논문지
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• 제14권4호
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• pp.87-92
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• 2018

One of the problems with the base station equipment is that there is a large difference between the replacement time of the hardware equipment such as the base station equipment and the radio access equipment, and the evolution period of the communication standard. Therefore, the base station communication platform must be flexible enough to handle the evolving communication standards after purchase. Recent research on reconfigurable communications platforms has focused on the efficient architecture of the communications platform to meet these requirements through software downloads while still using existing hardware. This paper presents a prototype of a base station communications platform based on the ETSI standard reconfigurable architecture. The communication platform presented in this paper is implemented as an ETSI standard reconfigurable architecture using a general-purpose DSP (Digital Signal Processor). In the implemented prototype, we verify the real-time feasibility of communication protocol updates through software reconfiguration.

• 디지털산업정보학회논문지
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• 제12권4호
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• pp.81-87
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• 2016

Recently, as the heterogeneous network (HetNet) has been deployed widely to support various kinds of Radio Access Networks(RANs) with a combination of Macro, Pico, and/or Femto cells, research and standardization efforts have been very active regarding the concept of Licensed Shared Access (LSA) for supporting spectrum sharing. In order for a mobile device to efficiently support the spectrum sharing, the mobile device shall be reconfigurable, meaning that its radio application code has to be adaptively changed in accordance with the hopping of desired spectral band. Especially, Working Group 2 (WG2) of Technical Committee (TC) Reconfigurable Radio System (RRS) of European Telecommunications Standards Institute (ETSI) has been a main driving force for developing standard architecture for Multi-mode Mobile Device (MD) that can be applied to the LSA system. In this paper, we introduce the Multi-mode MD architecture for supporting LSA-based spectrum sharing. An implementation of a test-bed of Multi-mode MD is presented in order to verify the feasibility of the standard MD architecture for the purpose of LSA-based spectrum sharing through various experimental tests.

• 인터넷정보학회논문지
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• 제7권2호
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• pp.121-136
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• 2006

재구성(reconfiguration) 기능을 갖춘 SDR(Software Defined Radio) 시스템이 가져야할 소프트웨어 아키텍처와 컴포넌트들 사이에 필요한 프로토콜에 대한 분석을 수행하고 기능 구현을 위한 시스템 설계 내용을 제시한다. 이를 위해 SDR의 기술동향을 분석하고, SDR 시스템을 구축하기 위한 모델을 임베디드 시스템 (Imbedded System)에 입각하여 설계하였다. SDR 시스템 아키텍처는 하드웨어, 운영체제, 미들웨어, 서비스 객체, 응용 계층으로 이루어지는 5계층 구조를 제시한다. SDR 시스템은 리눅스 운영체제 기반에서 구축하였으며, SDR의 주요 특징인 확장성 (scalability)과 재구성 기능이 상호보완적이 되도록 하였다. 5계층 구조에서 SDR의 핵심 기능인 소프트웨어 다운로드 (Software Download) 기능을 구현하기 위한 프로토콜 및 객체의 상태천이도를 수용하는 소프트웨어 설계 내용을 제시한다.

• Journal of Communications and Networks
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• 제18권2호
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• pp.135-149
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• 2016

Cloud radio access network (C-RAN) refers to the virtualization of base station functionalities by means of cloud computing. This results in a novel cellular architecture in which low-cost wireless access points, known as radio units or remote radio heads, are centrally managed by a reconfigurable centralized "cloud", or central, unit. C-RAN allows operators to reduce the capital and operating expenses needed to deploy and maintain dense heterogeneous networks. This critical advantage, along with spectral efficiency, statistical multiplexing and load balancing gains, make C-RAN well positioned to be one of the key technologies in the development of 5G systems. In this paper, a succinct overview is presented regarding the state of the art on the research on C-RAN with emphasis on fronthaul compression, baseband processing, medium access control, resource allocation, system-level considerations and standardization efforts.

• ETRI Journal
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• 제33권5호
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• pp.802-805
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• 2011

This letter presents a K-band polarization reconfigurable antenna integrated with a silicon radio frequency MEMS switch into the form of a compact package. The proposed antenna can change its state from linear polarization (LP) to circular polarization (CP) by actuating the MEMS switch, which controls the configuration of the coupling ring slot. Low-loss quartz is used for a radiating patch substrate and at the same time for a packaging lid by stacking it onto the MEMS substrate, which can increase the system integrity. The fabricated antenna shows broadband impedance matching and exhibits high axial ratios better than 15 dB in the LP and small axial ratios in the CP, with a minimum value of 0.002 dB at 20.8 GHz in the K-band.

• Journal of Positioning, Navigation, and Timing
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• 제10권2호
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• pp.91-102
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• 2021

In this paper, a fully reconfigurable Software Defined Radio (SDR) for multi-constellation and multi-frequency Global Navigation Satellite System (GNSS) receivers is presented. The reconfigurability with respect to the data structure, variability of signal and receiver parameters, and receiver's internal functionality is presented. The configuration file, that is modified to lead to an entirely different operation of the SDR in response to specific target signal scenarios, directly determines the operating characteristics of the SDR. In this manner, receiver designers can effectively reduce the effort to develop many different combinations of multi-constellation and/or multi-frequency GNSS receivers. Finally, the implementation of the presented fully reconfigurable SDR is included with the experimental processing results such as acquisition, tracking, navigation for the received signals in the realistic fields.

• 전자통신동향분석
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• 제36권3호
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• pp.119-132
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• 2021

To accommodate various mobile communication frequency bands, the study of metamaterial antennas have begun since the mid-2000s to solve the Trilemma problem between antenna gain-occupied bandwidth-size. As an adaptive reconfiguration function is required in a multi-array antenna system since 4G, the metamaterial array antenna using low-power variable elements has been used to change the basic structure of the antenna. Recently, reconfigurable intelligent surface (RIS), which is made of metasurface with reconfigurability, has been studied to effectively cope with the randomly varying radio channels and be used for various purposes such as reflection/transmission/modulation. As a result of RIS-related patent information analysis in this study, it was confirmed that most of the patents are metamaterial antennas and metamaterial array antennas, but the metasurface antenna technology was in the early stages. Particularly, as the intelligent metasurface antenna is in a more initial stage, the investment to R&D of RIS is urgent to secure patent competitiveness in B5G and 6G.

• ETRI Journal
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• 제33권3호
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• pp.326-334
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• 2011

This paper outlines the time jitter effect of a sampling clock on a software-defined radio technology-based digital intermediate frequency (IF) transceiver for a mobile communication base station. The implemented digital IF transceiver is reconfigurable to high-speed data packet access (HSDPA) and three bandwidth profiles: 1.75 MHz, 3.5 MHz, and 7 MHz, each incorporating the IEEE 802.16d worldwide interoperability for microwave access (WiMAX) standard. This paper examines the relationship between the signal-to-noise ratio (SNR) characteristics of a digital IF transceiver with an under-sampling scheme and the sampling jitter effect on a multichannel orthogonal frequency-division multiplexing (OFDM) signal. The simulation and experimental results show that the SNR of the OFDM system with narrower band profiles is more susceptible to sampling clock jitter than systems with relatively wider band profiles. Further, for systems with a comparable bandwidth, HSDPA outperforms WiMAX, for example, a 5 dB error vector magnitude improvement at 15 picoseconds time jitter for a bandwidth of WiMAX 3.5 MHz profile.

• Journal of Ubiquitous Convergence Technology
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• 제2권2호
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• pp.59-66
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• 2008

In this study, Software Defined Radio (SDR) technology-based digital filterbank architecture applicable to a multiple-channel processing system such as a wireless mobile communication system using Code Division Multiple Access (CDMA) technology is proposed. The technique includes a micro-processor to redesign Finite Impulse Response (FIR) filter coefficients according to specific system information and to download the filter coefficients to one digital Band Pass Filter (BPF) to reconfigure another system. The feasibility of the algorithm is verified by computer simulation and by implementing a multiple-channel signal generator that is reconfigurable to other system profiles, including those of a Wideband Code Division Multiple Access (WCDMA) system and a CDMA system.