• 한국멀티미디어학회논문지
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• 제11권12호
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• pp.1697-1705
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• 2008

Several studies made for wireless mesh networks aim to optimize the capacity for wireless networks. Aside from protocol improvements, researches were also done on the physical layer particularly on modulation techniques and antenna efficiency schemes. This paper is concerned with the capacity improvements derived from using spatial diversity with smart adaptive array antennas. The use of spatial diversity, which has been widely proposed for use in cellular networks in order to lessen frequency re-use, can be used in mesh networks both to minimize co-channel interference (CCI) and enable multiple transmissions. This paper aims to study the capacity region and bounds in using smart antennas for single-channel multi-radio systems in relation to the number of spatial diversity or sectors as defined by the beam angle $\beta$.

• 한국전자파학회논문지
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• 제25권8호
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• pp.808-820
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• 2014

본 논문에서는 10-dB 감쇠기 및 상용 패키지 된 MMIC 능동소자를 이용하여 구성된 증폭기, 2가지의 온-웨이퍼(on-wafer)형 DUT(Device-Under Test)를 구성하고, 이들의 잡음파라미터를 8-port 회로망을 이용하여 추출하는 방법을 제시하였다. 제작된 10-dB 감쇠기의 경우 수동소자이기 때문에, 이것의 S-파라미터를 측정하여 얻을 경우, 이것의 잡음파라미터를 알 수 있고, 또한 증폭기의 경우 이것의 잡음파라미터가 datasheet에 있다. 따라서 제안한 방법을 이용한 잡음파라미터 측정 결과에 대한 평가를 용이하게 할 수 있다. 기존 저자들에 의하여 발표된 6-포트회로망을 확장한 8-포트회로망을 이용한 잡음파라미터 측정은 사용된 8-포트회로망의 S-파라미터를 필요로 하는데, 동축형 DUT에 국한된다. 온-웨이퍼 프로브가 8-포트회로망에 삽입될 경우, 8-포트회로망의 S-파라미터 측정은 이종 형태의 커넥터를 갖는 8-포트회로망이 된다. 본 논문에서는 회로망 분석기(Network analyzer)의 Smart-cal 기능을 이용하여 8-포트회로망의 S-파라미터를 추출하였다. 측정된 잡음파라미터는 최소잡음지수, $NF_{min}$ 경우, 예상된 결과에 대하여 약 ${\pm}0.2dB$의 오차를 보인다. 다른 잡음파라미터는 주파수에 따라 예상된 결과와 근접하게 일치하는 결과를 보여주고 있다.

• 한국산학기술학회논문지
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• 제16권7호
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• pp.4842-4848
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• 2015

본 논문은 재구성 빔 스티어링 안테나와 전방향성(루프) 안테나 간 정지상태와 이동상태일 때 통신 성능 비교를 보여준다. 두 안테나는 동일한 직물(${\varepsilon}_r=1.35$, $tqn{\delta}=0.02$) 위에 제작되었으며 5 GHz 대역에서 동작한다. 재구성 안테나는 빔 방향을 조향할 수 있도록 설계되었다. 빔 스티어링 기능을 수행하기 위해 안테나는 두 개의 핀 다이오드를 사용한다. 측정된 최대 이득은 5.9-6.6 dBi 이고 반 전력 빔 폭(HPBW)는 $102^{\circ}$ 이다. 통신효율을 비교하기 위해 GNU Radio Companion 소프트웨어툴과 USRP(User Software Radio Peripheral) 장비를 이용하여 두 안테나의 BER(Bit Error Rate)과 SNR(Signal-to-Noise Ratio)를 측정하였다. 그리고 송, 수신 안테나 사이의 일정한 거리에서 수신 안테나가 고정된 상태와 이동중인 상태 두 가지 경우를 비교하였다. 본 측정은 이상적인 전파환경인 무손실 안테나 챔버와 전파간섭이 존재하는 실제적인 환경인 스마트홈에서 진행되었다. 본 측정의 결과로 빔 스티어링 안테나의 성능이 루프 안테나보다 우수함을 알 수 있다. 또한, 통신효율을 비교하면 측정환경 측면에서는 무손실 안테나 챔버가 스마트홈보다 우수하며, 안테나의 고정/이동 측면에서는 고정된 상태가 이동중인 상태보다 좋은 결과를 보임을 알 수 있다.

• 전기전자학회논문지
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• 제12권2호
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• pp.81-86
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• 2008

In wireless communication system using 2.4GHz radio link, data rate varies with time due to interferences, which causes the performance degradation. Therefore, effective transmission methods are required to obtain better performance according to varying data rate. This paper proposes a novel method that increases the data rate, as well as the influence of different loop-filter bandwidths on the performance of the PLL. Experimental results show that the proposed method is effective because it can achieve higher throughput in various data rate.

• International journal of advanced smart convergence
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• 제4권2호
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• pp.177-185
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• 2015

In this paper we introduce Kernel Fisher Discriminant Analysis (KFDA) to transform our database of received signal strength (RSS) measurements into a smaller dimension space to maximize the difference between reference points (RP) as possible. By KFDA, we can efficiently utilize RSS data than other method so that we can achieve a better performance.

• 한국융합학회논문지
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• 제2권4호
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• pp.1-7
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• 2011

IT의 발전으로 기기 간 통신을 이용하는 M2M 시장이 급성장하고 있으며, 많은 기업들이 M2M 사업에 참여하고 있다. 본 논문에서는 텔레매틱스의 개념 및 차량 네트워크 보안의 취약성을 알아보았다. 차량 및 IT 기술의 융합과 이동통신망 기술의 발전은 사용자에게 제공되는 서비스의 질은 향상 시켰지만, 이로 인한 보안 위협은 다양해졌다. 텔레매틱스 사업에서 이동통신사업자의 참여로 생성될 수 있는 새로운 비즈니스 모델을 제시하였으며, 이러한 환경에서 발생 될 수 있는 차량 이동통신망 보안 취약성을 분석하였다. 이 중 발생할 수 있는 취약성을 해결하기 위한 방법으로 M2M 기기와 스마트폰 및 차량 상호 인증 기법을 제시하였다.

• 정보통신설비학회논문지
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• 제5권1호
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• pp.43-59
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• 2006

A compact and broadband $4\times1$ array antenna was developed for 3G smart antenna system testbed. The $4\times1$ uniform linear away antenna was designed to operate at 1.885 to 2.2GHz with a total bandwidth of 315MHz. The array elements were based on the novel broadband L-probe fed inverted hybrid E-H (LIEH) shaped microstrip patch, which offers 22% size reduction to the conventional rectangular microstrip patch antenna. For steering the antenna beam, a commercial variable attenuator (KAT1D04SA002), a variable phase shifter (KPH350SC00) with four units each, and the corporate 4-ways Wilkinson power divider which was fabricated in-house were integrated to form the beamforming feed network. The developed antenna has an impedance bandwidth of 17.32% $(VSWR\leq1.5)$, 21.78% $(VSWR\leq2)$ with respect to center frequency 2.02GHz and with an achievable gain of 11.9dBi. The design antenna offer a broadband, compact and mobile solution for a 3G smart antenna testbed to fully characterized the IMT-2000 radio specifications and system performances.

• 정보통신설비학회논문지
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• 제7권1호
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• pp.41-58
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• 2007

A compact and broadband $4{\times}1$ array antenna was developed for 3G smart antenna system testbed. The $4{\times}1$ uniform linear array antenna was designed to operate at 1.885 to 2.2GHz with a total bandwidth of 315MHz. The array elements were based on the novel broadband L-probe fed inverted hybrid E-H (LIEH) shaped microstrip patch, which offers 22% size reduction to the conventional rectangular microstrip patch antenna. For steering the antenna beam, a commercial variable attenuator (KAT1D04SA002), a variable phase shifter (KPH350SC00) with four units each, and the corporate 4-ways Wilkinson power divider which was fabricated in-house were integrated to form the beamforming feed network. The developed antenna has an impedance bandwidth of 17.32% ($VSWR{\leq}1.5$), 21.78% ($VSWR{\leq}2$) with respect to center frequency 2.02GHz and with an achievable gain of 11.9dBi. The design antenna offer a broadband, compact and mobile solution for a 3G smart antenna testbed to fully characterized the IMT-2000 radio specifications and system performances.

• International journal of advanced smart convergence
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• 제1권2호
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• pp.59-63
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• 2012

The mVoIP service is the technology which focuses on the wireless data service as the IP network having the transmission rate of 100 Mbps classes on the high-speed middle of movement through the WiFi, WiBro and 3G mobile radio communication network, and etc. and is developed. Since 2010, the mVoIP (mobile VoIP) service shows the rapid growth due to 4G-LTE service seriously disclosed from July with the Smart phone and 2,011 it begins to be rapidly popularized. In this research, additionally the mVoIP service industry activation plan is presented with the trends of technology development including the chip-set/module/terminal, etc. based upon local and foreign market trend searchlight through the market demand analysis. The mVoIP service downloads App to the mobile apparatus and or can provide the service as the software through the WiFi network. Therefore, the change which is large in the products development aspect is to be have no. Expected to is being provided as the added service in the case of 4G-LTE as a matter of course, the service deployment where it is based on the market principle and demand needs is needed.

• 한국멀티미디어학회논문지
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• 제16권5호
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• pp.566-576
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• 2013

In Home Area Network (HAN) of the smart grid, Power Line Communication (PLC) technology and ZigBee communication technology can be used in the communication among the Advanced Metering Infrastructure (AMI) devices. However, according to performance evaluation results of the PLC technology, we find that using the PLC technology is unsuitable for the remote meter reading service. It is worth noting that some parts of the PLC are converted to the ZigBee communication technology in Jeju, Korea. Compared with PLC, ZigBee has no restriction of the place, where the equipments can be freely set up, due to the advantage of radio communication. However, number of usable devices will impact the network performance which is depended on the address assignment. In addition, due to the restriction of transmission range among devices, it is difficult to apply the ZigBee address assignment method to the practical circumstance. In this paper, we examine the previous ZigBee address assignment schemes and the corresponding routing algorithms, and propose a novel address assignment scheme compared with the existing methods, the performance of the proposed one is improved. In particular, evaluation results show that the proposed scheme reduces the average number of hop count, the transfer time and the processing time.