Browsing by Author "Hou, Hsin-An"

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A Systematic Approach to Improve Fiber-Wireless Access Network in High Speed Railway Tunnels
(2015)
Hou, Hsin-An
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Wang, Li-Chun
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傳播研究所
;
Institute of Communication Studies
Wireless access networks over high speed railway (HSR) encounters many challenges, e.g., the fluctuations of wireless channels, frame synchronization, and geographical obstacles. Since increasing signal quality can bring benefit against channel impairments, the key to solve these challenges is to enhance radio signal strength over HSR. Combining radio over fiber with distributed antennas system (RoF-DAS) can improve radio link quality on a high speed train over HSR, especially in tunnels and underground. Compared to leaky cable, RoF-DAS is easier to be deployed and lower cost. However, the effects of multi path fading and Doppler shift can seriously degrade the performance of RoF-DAS. In this paper, we present a systematic methodology to determine the enhanced configuration for RoF-DAS, such as power attenuation values and propagation time. The proposed systematic methodology takes the joint effect of channel dispersion and Doppler effect, and different deployment scenarios into account to determine the RoF-DAS configuration. Our simulation results also show that performance of RoF-DAS with configuration by the proposed methodology are better than the other configurations.
An Antenna Control Mechanism for Distributed Antenna Systems Over High-Speed Railway Communications
(2013)
Wang, Hung-Hsiang
;
Hou, Hsin-An
;
Chen, Jyh-Cheng
;
傳播研究所
;
Institute of Communication Studies
Providing broadband wireless services over highspeed railways with Distributed Antenna Systems (DAS) has attracted much attention in recent years. In this paper, we analyze the issues of Time Division Duplex (TDD) DAS, including coverage of Remote Antenna Units (RAUs) and echo channel effect. Also, the timing drift problem while solving the effects of echo on the channel with moving cell in TDD-DAS is investigated. To overcome these problems, we propose techniques for antenna selection with timing compensation. Simulation results show that both the echo channel issue and dilemma between coverage and cost can be solved effectively. Finally, further research studies on enhancing DAS with more intelligence functions such as power saving and resource management are discussed.
Analysis on Time-Variant Air-to-Ground Radio Communication Channel for Rotary-Wing UAVs
(2019-01-01)
Hou, Hsin-An
;
Wang, Li-Chun
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電信工程研究所
;
Institute of Communications Engineering
With the inertial measurement unit (IMU) and motor technology improvement, the unmanned aerial vehicles (UAVs) become more accessible for different applications. Among the fixed-wing and the rotary-wing UAV, the former is advantageous in having no runway and small craft size which are more attractive to users. The rotary-wing UAVs is used to provide real-time monitor and control on interest targets for ground users. However, the effects of propellers are not addressed in existing rotary-wing UAV channel models. In this paper, we propose a simple air-to-ground radio communication channel for rotary-wing UAVs considering the propellers. Analysis and results are presented based on the model. The results show the maximum of Doppler shifts for all simulated frequencies exceed 300Hz, the requirement of the LTE, and there is potential risks adapt the current communication system directly for serious time-variant multipath and Doppler frequency shift channel issues.
Area Spectral Efficiency for Cellular Networks with Small Reuse Distance: An Algebraic Approach
(2017-01-01)
Hou, Hsin-An
;
Wang, Li-Chun
;
電信工程研究所
;
Institute of Communications Engineering
In this paper we present an algebraic analytical approach to estimate area spectrum efficiency (ASE) of interference-limited cellular mobile systems with small reuse distance ratio. In an ultra-dense network (UDN), the co-channel inter-site distance is very small (e.g. 2 times of cell radius). However, to the best of our knowledge, an accurate performance framework for cellular mobile network with small number of co-channel inter-site distance ratio is rarely seen in the literature. To improve the accuracy of expression, we take interference signals from the all interfering BSs on two-dimension and area spectral efficiency (ASE) into account, and derive the close-form expression for the downlink signal-to-interference plus noise ratio (SINR) by Newton's generalized binomial equation and triangle identities of a base station (BS) geometry model. Based on the SINR expression, we further derive tight approximation formulas of downlink spectral efficiency (SE)s and ASE. Moreover, the SINR close-form expression and the tight approximation for SE and ASE with small reuse distance ratio are also presented and validated.
Design and Analysis of an Antenna Control Mechanism for Time Division Duplexing Distributed Antenna Systems Over High-Speed Rail Communications
(2016-10-12)
Wang, Hung-Hsiang
;
Hou, Hsin-An
;
Chen, Jyh-Cheng
;
資訊工程學系
;
電信工程研究所
Distributed antenna system (DAS) has been introduced to overcome high mobility issues and to extend signals into coverage-hole areas in high-speed rail communications system. In this paper, we discuss echo channel effect and define the corresponding criteria in a time division duplexing (TDD) DAS railway communications system. Furthermore, timing drift problem while applying moving antenna selection technique to solve the echo channel effect is illustrated. Compensation algorithms then are proposed. Simulation results show that the proposed techniques can not only solve the interference problem in TDD-DAS but also provide better scalability in system deployment.