Browsing by Author "Chen, Yuan-Kai"

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A Handset-Based Solution for Reducing International Roaming Costs
(2011-05-01)
Lin, Yi-Bing
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Liou, Ren-Huang
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Chen, Yuan-Kai
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Gan, Chai-Hien
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資訊工程學系
Today's mobile service providers allow their users to receive telecom services when they roam to other countries. However, international roaming is very expensive. In the standard mobile call setup procedure, a call from the visited country to a roaming user in that country results in two international calls. This phenomenon is referred to as the tromboning effect. Several third-party solutions have been proposed to resolve the tromboning problem by replacing two international calls with two local calls. These solutions require one or more gateways for call re-routing. This paper proposes a handset-based solution that does not need to add/modify network nodes in the existing mobile telecom systems. Analytic modeling and simulation experiments indicate that our solution is effective in international trunk elimination and call setup signaling.
Automatic event-triggered call-forwarding mechanism for mobile phones
(2013-08-25)
Lin, Yi-Bing
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Liou, Ren-Huang
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Chen, Yuan-Kai
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Wu, Zheng-Han
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資訊工程學系
Call forwarding is a traditional telecom service that allows a user to forward incoming calls to another telephone number. call-forwarding algorithm (CFA) for mobile phones. By installing a software in a smartphone, call forwarding is automatically triggered (e.g., when the phone is plugged in a charger or is turned off) or disabled (e.g., when the phone is unplugged from the charger or is turned on). We investigate the performance of the CFA through analytic analysis, simulation, and measurement. Our study indicates that CFA is very feasible for commercial usage. Copyright (c) 2011 John Wiley & Sons, Ltd.
Bearer Reservation with Preemption for Voice Call Continuity
(2009-05-01)
Lin, Yi-Bing
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Tsai, Meng-Hsun
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Dai, Hui-Wen
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Chen, Yuan-Kai
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資訊工程學系
In Universal Mobile Telecommunications System (UNITS), the core network consists of two service domains: the circuit-switched (CS) and the packet-switched (PS) domains. A UNITS handset can initiate or receive a call in either the CS or the PS domain. During the call, the user may switch from one domain to another. The switching overhead is an important concern of domain transfer. In this paper, we propose the Bearer Reservation with Preemption (BRP) scheme to support fast domain transfer, and present both analytic model and simulation experiments to investigate the BRP performance. Our study indicates that when user behavior is irregular (i.e., either the variance of the domain residence times or the variance of the call holding times is large), the advantage of the BRP scheme becomes significant.
DEPLOYING THE FIRST PSTN-BASED IOT MECHANISM
(2018-12-01)
Lin, Yi-Bing
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Lin, Rong-Syh
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Chen, Yuan-Kai
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Twu, Chin-Ywu
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Yang, Shun-Ren
Existing IoT services are based on data communications technologies that do not involve the public switched telephone network (PSTN). Since the telephone numbers have been assigned to machine-type devices, PSTN switches can play a role in IoT service routing. In this article we deploy a PSTN-based IoT mechanism where the interaction between the users and the IoT devices is achieved through PSTN switches. To our knowledge, this is the first PSTN-based IoT solution in the world. With this mechanism, all PSTN customer premises equipment (CPE; fixed-line and mobile phones) can access IoT services without installing any software (mobile apps). By reusing the existing PSTN infrastructure, PSTN-based IoT offers telecom-grade service, security, and network management for IoT, which are very expensive to build in non-PSTN-based IoT. Our approach conveniently enables the existing CPE to access IoT applications, which will significantly promote the IoT service industry.
DEPLOYMENT OF THE FIRST COMMERCIAL LWA SERVICE
(2017-12-01)
Tu, Yuan-Kuang
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Lee, Cheng-Hua
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Liu, Chia-Horng
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Chia, Chung-Yung
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Chen, Yuan-Kai
This column reports the deployment of the first commercial LWA service. The deployed LWA network reuses and is merged with the existing individual LTE and WLAN networks. Our experience indicates that this approach allows quick establishment of LWA service, which nicely resolves the coexistence problems arising from deploying the LTE system in unlicensed spectrums. Specifically, in the initial stage, selected LWA hotspots with the required service were built in two months. Through this deployment, we show how Chunghwa Telecom utilizes unlicensed spectrum to open up additional capacity to support LTE service. Specifically, the throughput of an LWA site can be more than twice of that for an LTE eNB. Also, through an LWA eNB, an LWA-capable user equipment can indirectly perform seamless handover between a Wi-Fi AP without mobility capability and a standard eNB. This indirect handover time is less than 400 ms plus the standard EAP-SIM authentication time for Wi-Fi.
PERFORMANCE MEASUREMENTS OF TD-LTE, WIMAX AND 3G SYSTEMS
(2013-06-01)
Lin, Yi-Bing
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Lin, Pin-Jen
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Sung, Yingrong Coral
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Chen, Yuan-Kai
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Chen, Whai-En
Long Term Evolution (LTE) and Worldwide Interoperability for Microwave Access (WiMAX) are two major technologies toward next-generation mobile broadband standards, which are both expected to provide higher throughput and lower transmission latency for mobile users. This article measures and compares the latency and the throughput of Time Division - Long Term Evolution (TD-LTE), WiMAX, and third-generation (3G) systems based on several technical trials. Our quantitative measures and comparisons provide guidelines for the operators to deploy their future networks.
Reducing International Call Costs for Roamer to Roamer Calls
(2010-10-01)
Chen, Yuan-Kai
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Lin, Yi-Bing
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Liou, Ren-Huang
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資訊工程學系
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Department of Computer Science
Existing mobile telecom operators allow subscribers to receive mobile phone services when they roam in other countries. However, call setup to an international roaming subscriber is indirectly routed through the home network of the subscriber, which results in the usage of two expensive international telephone trunks. In this paper, we propose a plug-in roaming gateway to avoid the international trunk connections. Our solution is especially attractive when both call parties are roamers.
Reducing International Call Costs for Roamer to Roamer Calls
(2010-10-01)
Chen, Yuan-Kai
;
Lin, Yi-Bing
;
Liou, Ren-Huang
;
資訊工程學系
;
Department of Computer Science
Existing mobile telecom operators allow subscribers to receive mobile phone services when they roam in other countries. However, call setup to an international roaming subscriber is indirectly routed through the home network of the subscriber, which results in the usage of two expensive international telephone trunks. In this paper, we propose a plug-in roaming gateway to avoid the international trunk connections. Our solution is especially attractive when both call parties are roamers.