• Proceedings of the Korean Society of Computer Information Conference
• /
• 2015.07a
• /
• pp.275-276
• /
• 2015

네트워크 가상화를 위한 대표적인 개방적 아키텍처로 OpenFow를 들 수 있다. OpenfFow는 가상 네트워크(Software Defined Network) 개념을 실현하기 위한 랜 스위치 제어 프로토콜의 집합체로서 데이터 센터 등 주로 유선랜 환경을 목표로 설계되어 활용되고 있다. 이 논문에서는 OpenFlow를 무선랜의 AP(Access Point)에 적용하여 WiFi 디바이스들로 구성된 가상 무선 네트워크 관리 프레임을 구현한다. 구현된 관리 프레임은 WiFi 디바이스들의 토폴로지와 트래픽 상황을 중앙 관제 센터에서 모니터링할 수 있고, 플로우 경로를 설정함으로써 라우터를 경유하지 않고 AP 수준에서 스위칭(라우팅)이 가능하여 전체적인 트래픽 혼잡을 크게 줄일 수 있다.

• Electronics and Telecommunications Trends
• /
• v.37 no.3
• /
• pp.1-10
• /
• 2022

Traditional centralized radio access network architecture used for 4G is based on Option 8, a functional split between PHY and RF. This option is commonly used with a fronthaul interface based on common public radio interface (CPRI) specifications; however, the increased data rates in 5G make this option impractical because of the fronthaul interface's high bandwidth requirement. Since CPRI specifications have many vendor-specific options, achieving multi-vendor interoperability becomes challenging. Open RAN (O-RAN) Alliance is developing novel open fronthaul interface specifications based on the functional split Option 7-2x, one of the intra-PHY split options, to relax the bandwidth requirement of the fronthaul interface and achieve multi-vendor interoperability. This article provides a brief overview of the various functional split options for 5G fronthaul that have been reported so far and existing fronthaul technologies. Further, the technological trends in the 5G open fronthaul interface is discussed, focusing on the O-RAN Alliance specifications under standardization.

• Information and Communications Magazine
• /
• v.32 no.4
• /
• pp.3-9
• /
• 2015

무선 메쉬 네트워크는 자가 구성(Self-organizing), 자가 회복(Self-healing)등의 특징으로 인해 u-Office 환경을 구축함에 있어 핵심 기술로 여겨지고 있다. 본 논문에서는 무선 메쉬 네트워크의 기술 동향을 파악하고 또한 무선랜 라우터를 위한 비실시간 리눅스 기반의 오픈 소스 운영체제인 OpenWrt와 소프트웨어적으로 네트워크를 컨트롤하는 기술인 Openflow 를 기반으로 한 무선 메쉬 네트워크 테스트베드의 구축 사례와 실측 사례를 서술한다.

• Journal of Digital Contents Society
• /
• v.19 no.8
• /
• pp.1545-1554
• /
• 2018

In order to support the mobility of the wireless devices, at least two APs (Access Points) must be arranged in a single AP area to maintain communication area. In the WLAN (Wireless LAN) environment, seamless handover is one of the most important issues in terms of effective utilization of wireless networks and maximization of services for users. On the other hand, SDN (Software-Defined Networking), which is emerging rapidly in recent years, is revolutionizing network management in terms of flexibility, fine control, and convenience. SDN originally reduces latency time or increases network robustness by real-time flow table control reducing or bypassing paths between switches in LAN-based data centers. In this study, we apply OpenFlow, a SDN platform focused on wired LAN, to a dense WLAN environment using legacy APs to implement and evaluate seamless handover for streaming services of digital contents.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.22 no.11
• /
• pp.1101-1110
• /
• 2011

This paper presents a printed, wideband folded monopole antenna for laptop and tablet computer applications. The proposed antenna is designed to cover bandwidth(2.3~10.6 GHz) of Bluetooth, WiMAX, and UWB system by using the printed folded monopole antenna having asymmetrical line width coupling with a parasitic inverted- L element. Also, wireless LAN band(5.15~5.85 GHz) which interferes with UWB system is rejected by inserting half-wavelength open stub in the folded monopole antenna. -10 dB bandwidth of the fabricated wideband antenna is 2.27~10.6 GHz (4.7:1) and -10 dB band-rejected bandwidth is measured as 700 MHz(5.15~5.85 GHz, 12.72 %). The gain and efficiency of the antenna except for the rejected band are higher than 3.93 dBi and 91.89 % and are measured as -2 dBi and 14.65 % at 5.5 GHz which is band-rejected frequency. The size of the antenna is suitable to install for small space of tablet and laptop computers as 12.75(1 ${\lambda}$/10)${\times}$12(1 ${\lambda}$/11) $mm^2$(${\lambda}$ is free space wavelength at 2.3 GHz). Therefore, we verified that the designed antenna is appropriate for wideband antenna of tablet and laptop PC applications.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.46 no.9
• /
• pp.60-65
• /
• 2009

In this paper, we present a compact Ultra-Wideband band-pass later with notched band at fireless-LAN band using a band-pass and band-notch filter. The structure of our proposed band-pass filter is very simple, and the DGS(Defected Ground Structure) structure is used to get the low-pass filter characteristic, and an embedded open-stub structure is used to get the notched filter. Our proposed band-pass filter can be much smaller than a cascaded filter. As a result of measurement, the insertion loss is less than 0.7dB throughout the pass-band of $2.21GHz{\sim}10.92GHz$, the return loss is more than 17dB and the group delay maximum variation is 0.24ns and a notched band is at $5.3GHz{\sim}5.7GHz$.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.17 no.3
• /
• pp.336-342
• /
• 2007

Industrial HMI(Human Machine Interface) system is the main element among the factory automation processes and have been used to monitor and control operation and status of machine in factory with PLC. This HMI often brings heavy loads to the system development and difficult decreasing the system because it tends to use a specific system per each manufacturer. Therefore, in this thesis, we have developed an embedded linux-based embedded industrial HMI software modules which can be used for touch panel embedded system to solve these problem. In this module, we have used the Qt/Embedded software component because it can be used by all systems which support C++ compiler without modifying the existing codes. We can design more flexible system and network configuration because we have used the wireless communication module. In this thesis, we implement linux-based HMI software modules which are capable of wireless communication as well as bringing the mobility to the overall system and finally decreasing the system development loads by using the general purpose OS with competitive price.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.43 no.12 s.354
• /
• pp.55-64
• /
• 2006

This work proposes a calibration-free 14b 70MS/s 0.13um CMOS ADC for high-performance integrated systems such as WLAN and high-definition video systems simultaneously requiring high resolution, low power, and small size at high speed. The proposed ADC employs signal insensitive 3-D fully symmetric layout techniques in two MDACs for high matching accuracy without any calibration. A three-stage pipeline architecture minimizes power consumption and chip area at the target resolution and sampling rate. The input SHA with a controlled trans-conductance ratio of two amplifier stages simultaneously achieves high gain and high phase margin with gate-bootstrapped sampling switches for 14b input accuracy at the Nyquist frequency. A back-end sub-ranging flash ADC with open-loop offset cancellation and interpolation achieves 6b accuracy at 70MS/s. Low-noise current and voltage references are employed on chip with optional off-chip reference voltages. The prototype ADC implemented in a 0.13um CMOS is based on a 0.35um minimum channel length for 2.5V applications. The measured DNL and INL are within 0.65LSB and l.80LSB, respectively. The prototype ADC shows maximum SNDR and SFDR of 66dB and 81dB and a power consumption of 235mW at 70MS/s. The active die area is $3.3mm^2$.