Browsing by Author "Lu, Yin-Chih"

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A concurrent transmission MAC protocol for enhancing throughout and avoiding spectrum sensing in cognitive radio
(2007)
Wang, Li-Chun
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Wang, Chung-Wei
;
Lu, Yin-Chih
;
Liu, Chuan-Ming
;
交大名義發表
For the cognitive radio (CR) network, a fundamental issue is how to identify the spectrum opportunities. First, each CR node determines whether there exists transmission opportunities on unlicensed bands. If not, this node will find other opportunity on licensed bands. Thus, increasing the opportunities of concurrent transmissions in unlicensed bands can reduce the overhead of wide-band sensing. In this paper, based on the carrier sensing multiple access protocol, we propose a novel concurrent transmissions MAC (CT-MAC) protocol to identify the possibility of establishing the second link in the presence of the first link in the unlicensed band. In addition to reducing the overhead of wide-band sensing, the proposed CT-MAC scheme can enhance overall throughput and is backward compatible with the IEEE 802.11 standard.
iTraffic: A Smartphone-based Traffic Information System
(2013)
Chuang, Yi-Ta
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Yi, Chih-Wei
;
Lu, Yin-Chih
;
Tsai, Pei-Chuan
;
資訊工程學系
We propose the i-Traffic system that utilizes crowdsourced data from smartphones for the traffic flow mining by shockwave techniques. Shockwave is the propagation phenomenon of vehicle accumulation or relief on roads between two traffic flows with different speeds. The movement data of vehicles in front of an intersection are collected via smartphones for the shockwave identification. To conquer the low penetration problem when the number of the movement data is low, a folding heuristic is proposed by using traffic light cycle information to virtually increase the penetration of movement data. We implement our system on a client-server architecture and perform a small scale field trial experiment to demonstrate the system capability. Our results showed that our system is able to compute traffic information, including red/green light transition information and vehicle arrival rate with mean absolute errors of 5.0/0.6 seconds and 2.43 vehicles per minute, respectively under a low penetration rate of 1.2%.
Latency analysis for dynamic spectrum access in cognitive radio: Dedicated or embedded control channel?
(2007)
Wang, Li-Chun
;
Lu, Yin-Chih
;
Wang, Chung-Wei
;
Wei, David S. L.
;
交大名義發表
Dynamic spectrum access (DSA) is the key feature of cognitive radio (CR) networks, but it also poses many new challenges on the medium access control (MAC) design. One of key challenges is the fact that the secondary CR users can only borrow the licensed spectrum from the primary users for a short period of time. Hence, unlike many available multi-channel MAC protocols for ad hoc networks where throughput is the main performance issue, the DSA protocols in CR networks shall place more emphases on the access latency. Hence, one fundamental issue arises: how can the spectrum be dimensioned for control channels in order to minimize the access delay of DSA protocol in CR networks? In this paper, we provide a comparative study in an analytical manner on the latency performance of two DSA protocols: 1) dedicated control channel, and 2) embedded dedicated control channel approaches. Our results show that an optimal ratio of the control channel bandwidth over the total channel bandwidth can be found to minimize the latency of DSA with dedicated control channels. However, the delay performance of DSA with dedicated control channels is more sensitive to the variations of the data lengths than that of DSA with embedded control channels. Hence, we conclude that the way of dimensioning the spectrum for control frames for DSA in CR networks should be adaptive to the variations of the traffic characteristics and the number of users.