• Journal of Communications and Networks
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• 제11권2호
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• pp.175-186
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• 2009

A new medium access control (MAC) scheme embedding physical channels into multiband carrier sense multiple access/collision avoidance (CSMA/CA) networks is proposed to provide strict quality of service (QoS) guarantee to high priority users. In the proposed scheme, two priority classes of users, primary and secondary users, are supported. For primary users physical channels are provided to ensure strict QoS, whereas secondary users are provided with best-effort service using CSMA/CA modified for multiband operation. The performance of the proposed MAC scheme is investigated using a new multiband CSMA/CA Markov chain model capturing the primary user activity and the operation of secondary users in multiple bands. The throughput of secondary users is obtained as a function of the primary user activity and other CSMA/CA parameters. It is shown that the new MAC scheme yields larger throughput than the conventional single-band CSMA/CA when both schemes use the same bandwidth.

• Investigative Magnetic Resonance Imaging
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• 제20권1호
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• pp.27-35
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• 2016

Purpose: Among RF pulses, a sinc pulse is typically used for slice selection due to its frequency-selective feature. When a sinc pulse is implemented in practice, it needs to be apodized to avoid truncation artifacts at the expense of broadening the transition region of the excited-band profile. Here a sinc pulse tailored by a new apodization function is proposed that produces a sharper transition region with well suppression of truncation artifacts in comparison with conventional tailored sinc pulses. A multiband pulse designed using this newly apodized sinc pulse is also suggested inheriting the better performance of the newly apodized sinc pulse. Materials and Methods: A new apodization function is introduced to taper a sinc pulse, playing a role to slightly shift the first zero-crossing of a tailored sinc pulse from the peak of the main lobe and thereby producing a narrower bandwidth as well as a sharper pass-band in the excitation profile. The newly apodized sinc pulse was also utilized to design a multiband pulse which inherits the performance of its constituent. Performances of the proposed sinc pulse and the multiband pulse generated with it were demonstrated by Bloch simulation and phantom imaging. Results: In both simulations and experiments, the newly apodized sinc pulse yielded a narrower bandwidth and a sharper transition of the pass-band profile with a desirable degree of side-lobe suppression than the commonly used Hanning-windowed sinc pulse. The multiband pulse designed using the newly apodized sinc pulse also showed the better performance in multi-slice excitation than the one designed with the Hanning-windowed sinc pulse. Conclusion: The new tailored sinc pulse proposed here provides a better performance in slice (or slab) selection than conventional tailored sinc pulses. Thanks to the availability of analytical expression, it can also be utilized for multiband pulse design with great flexibility and readiness in implementation, transferring its better performance.

• ETRI Journal
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• 제36권5호
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• pp.835-840
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• 2014

New ways of achieving small, multiband, multifunctional, and standard solutions for mobile handset antennas are demanded in the current wireless market. A non-resonant element of $5mm{\times}5mm{\times}5mm$, a matching network, and a $100mm{\times}40mm$ slotted ground plane are proposed to satisfy mobile market demands that require multiband operation and small antenna solutions. The main advantage of the proposed design is that with only one non-resonant element of considerably small size ($0.015{\lambda}$, 900 MHz), the handset is capable of providing operation at mobile bands.

• Journal of information and communication convergence engineering
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• 제9권5호
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• pp.523-529
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• 2011

In this paper an inter-layer protocol, referred to as a Multi-Network Selector (MNS) is proposed for multiband maritime networks. A MNS is located between the data-link layer and the network layer and performs vertical handover when a ship moves another radio network. In order to provide seamless data transfer to different radio networks, the MNS uses received signal strength (RSS) and ship's location information as decision parameters for vertical handover, which can avoid ping-pong effect and reduces handover latency. In addition, we present related issues in order to implement the MNS for a multiband maritime network.

• 한국음향학회지
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• 제40권4호
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• pp.370-381
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• 2021

본 논문에서는 수중 통신에서 은밀성과 성능 향상을 위해 직접 수열 확산 방식 기반 다중 밴드 기법을 사용한 부 대역 Frequency Shift Keying(FSK) 신호의 효율적인 송수신 구조를 제시하였다. 은밀성적인 측면에서는 Pseudo Noise(PN) 부호의 chip을 직접 곱하는 직접 수열 대역 확산 방식을 적용하였으며, 성능적인 측면에서는 다중 경로 특성, 도플러 확산 등으로 인한 성능 감쇠를 극복하기 위해 다중 밴드, 터보 등화, 각 밴드별 가중치 알고리즘을 적용하였다. 시뮬레이션 결과를 바탕으로, 송수신기 사이의 거리가 약 300 m ~ 500 m인 호수에서 기동 실험을 하여 대역확산 신호의 chip 수를 8개, 32개로, 다중 밴드 수는 4개 일 때의 성능을 분석하였으며, chip 수가 증가할수록, 터보 등화 기법 적용 시 반복횟수가 증가할수록 성능이 향상되었고, 다중 밴드에서 프리엠블 오류율을 분석하여 밴드 별 가중치를 적용 시 더 많은 패킷 전송 성공률을 나타냈다.

• 한국ITS학회:학술대회논문집
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• 한국ITS학회 2010년도 춘계학술대회
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• pp.168-170
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• 2010

• 한국ITS학회:학술대회논문집
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• 한국ITS학회 2006년도 제5회 추계학술대회 및 정기총회
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• pp.191-194
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• 2006

• 한국ITS학회 논문지
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• 제6권3호
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• pp.111-121
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• 2007

된 논문은 국내 UWB 스펙트럼 환경에 적합하도록 펄스 성형을 통해 TH-UWB 시스템의 개념을 확장한 TH-Multiband-UWB 시스템을 구현하는 것을 그 목표로 한다. 이러한 펄스 성형을 위하여 Multi-Carrrier 형태의 전송 펄스를 제안하며, 간섭 주파수 검출을 위해 무선 인지 기술(Cognitive Radio)을 사용했다. 무선 인지 기술의 핵심이 되는 Cognitive Engine의 연산 알고리즘으로는 유전 알고리즘을 이용했다. 또한 성형된 펄스와 무선 인지 기술을 적용한 TH-UWB시스템이 동일 UWB 시스템을 비롯한 타 통신 시스템과의 간섭 상황을 해결하는 방법을 제시하였다. 이를 통해 본 논문은 무선 인지 엔진이 간섭 주파수를 찾아내는 방법을 알아보았고, 펄스 성형을 적용한 TH-UWB 시스템이 문제가 되는 간섭 상황을 해결하는데 뛰어난 성능이 있음을 확인하였다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제15권3호
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• pp.381-389
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• 2015

A fully integrated multistandard multiband CMOS mobile TV tuner with small silicon area and low power consumption is proposed for receiving multiple mobile digital TV signals and FM signal. In order to reduce the silicon area of the multistandard multiband receiver, other RF front-end circuits except LNAs are shared and a local oscillator (LO) signal generation architecture with a single VCO for a frequency synthesizer is proposed. To reduce the low frequency noise and the power consumption, a vertical NPN BJT is used in an analog baseband circuits. The RF tuner IC is implemented in a $0.18-{\mu}m$ CMOS technology. The RF tuner IC satisfies all specifications for DVB-H/T, T-DMB, and ISDB-T with a sufficient margin and a successful demonstration has been carried out for DVB-H/T, T-DMB, and ISDB-T with a digital demodulator.

• 전기전자학회논문지
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• 제19권2호
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• pp.124-132
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• 2015

In this paper, we proposed a multiband internal antenna for LTE mobile handset that could be used for mobile devices. The proposed antenna has a volume of $50mm(W){\times}21mm(L){\times}5mm(H)$, ground plane size is $60mm(W){\times}100mm(L)$, and covers 9 service frequency bands including LTE(Long Term Evolution) band with VSWR(Vlotage Standing Wave Ratio) less than 3. With rapid change of technologies, people wants to include more function into one device. In addition, each country uses different frequency band for traffic service, it is necessary to design multiband antenna for mobile phone since traveling foreign country needs roaming. And if we can cover several services with one antenna, cost and volume needed for antennas are minimized. A HFSS (High Frequency Structure Simulator) of the Ansoft Corporation based on a finite element method is employed to analyze the proposed antenna in the design process and to compare the simulation and experimental results.