• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권9호
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• pp.4123-4144
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• 2016

Vehicular Ad Hoc Networks (VANETs) utilize radio propagation models (RPMs) to predict path loss in vehicular environment. Modern urban vehicular environment contains road infrastructure units that include road tunnels, straight roads, curved roads flyovers and underpasses. Different RPMs were proposed in the past to predict path loss, but modern road infrastructure units especially flyovers and underpasses are neglected previously. Most of the existing RPMs are computationally complex and ignore some of the critical features such as impact of infrastructure units on the signal propagation and the effect of both static and moving radio obstacles on signal attenuation. Therefore, the existing RPMs are incapable of predicting path loss in flyovers and underpass accurately. This paper proposes an RPM to predict path loss for vehicular communication on flyovers and inside underpasses that considers both the static and moving radio obstacles while requiring only marginal overhead. The proposed RPM is validated based upon the field measurements in 5 GHz frequency band. A close agreement is found between the measured and predicted values of path loss.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권8호
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• pp.1933-1954
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• 2013

Multiple wireless devices are being widely deployed in Intelligent Transportation System (ITS) services on the road to establish end-to-end connection between vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) networks. Vehicular ad hoc networks (VANETs) play an important role in supporting V2V and V2I communications (also called V2X communications) in a variety of urban environments with distinct topological characteristics. In fact, obstacles such as big buildings, moving vehicles, trees, advertisement boards, traffic lights, etc. may block the radio signals in V2X communications. Their impact has been neglected in VANET research. In this paper, we present a realistic and efficient radio propagation model to handle different sizes of static and moving obstacles for V2X communications. In the proposed model, buildings and large moving vehicles are modeled as static and moving obstacles, and taken into account their impact on the packet reception rate, Line-of-sight (LOS) obstruction, and received signal power. We use unsymmetrical city map which has many dead-end roads and open faces. Each dead-end road and open faces are joined to the nearest edge making a polygon to model realistic obstacles. The simulation results of proposed model demonstrates better performance compared to some existing models, that shows proposed model can reflect more realistic simulation environments.

• 전자공학회논문지A
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• 제29A권4호
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• pp.7-13
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• 1992

Diffraction loss occurs when the propagation path is obstructed by mountains and hills between a base station antenna and a moving vehicle antenna in mobile-radio communication. In this paper an approximate mathematical model using Fresnel-Kirchhoff diffraction theory is considered to predict propogation attenuation by natural obstacles with lateral profiles having general shapes. Field tests are conducted using helical and crossed drooping dipole antenna at 820 MHz. The theoretical analysis used in estimating the effects of hills agrees reasonably with experimental data. The results seem to be useful for estimating the level of received power, the minimum allowable input power, the optimum site of base station and consequently, planning terrestrial microwave links.

• 한국통신학회논문지
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• 제37권4B호
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• pp.300-308
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• 2012

다양한 실내 위치 추적 기술들이 제안되고 있다. 일반적으로 TOA(Time of Arrival)신호를 활용한 실내 위치 추적 시에는 건물 내의 다양한 장애물들에 의해 전파의 굴절, 반사, 분산 등에 의해 위치 추적이 어렵다는 단점이 있다. 본 논문에서는 이러한 문제점을 해결하기 위해 NLOS(Non-Line-Of-Sight)환경에서 ETOA(Estimation-TOA) 알고리즘을 적용한다. ETOA알고리즘은 실내의 NLOS 환경이 발생한 해당 Beacon과의 TOA값을 추측항법을 통해 TOA값을 예측하는 알고리즘이다. 본 알고리즘을 이용하게 되면 삼각측량법을 사용하는 위치추적 시 3개의 노드 중 최대 2개의 노드가 NLOS가 발생하더라도 정확도 있는 위치 추적이 가능하다. 본 논문에서는 ETOA 알고리즘을 실내 이동로봇에 적용하고 로봇내의 관성센서와 칼만 필터를 이용함으로서 정확한 위치 추적을 할 수 있음을 확인하였다.