Browsing by Author "Gan, Chai-Hien"

Now showing 1 - 18 of 18

A Handset-Based Solution for Reducing International Roaming Costs
(2011-05-01)
Lin, Yi-Bing
;
Liou, Ren-Huang
;
Chen, Yuan-Kai
;
Gan, Chai-Hien
;
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.
A Multi-link Mechanism for Heterogeneous Radio Networks
(2014-06-01)
Yang, Shun-Neng
;
Lin, Yung-Chun
;
Gan, Chai-Hien
;
Lin, Yi-Bing
;
Wu, Chien-Ting
Nowadays, smart mobile devices drive the mobile traffic growth rapidly. Most smart mobile devices are equipped with multiple radio network interfaces, such as High Speed Packet Access (HSPA), Long Term Evolution (LTE), and Wi-Fi. Therefore, integration of multiple networks is a viable solution to fulfill traffic offloading and the Quality-of-Service (QoS) requirement of data usage for mobile users. In this paper, we propose a multi-link mechanism to handle the radio network selection and switching between LTE and Wi-Fi networks. A Multi-Link Adaptor (MLA) and a Multi-Connection Manager (MCM) are proposed for the User Equipment (UE) and the core network, respectively, to handle the multi-link mechanism. The applications executed in the UEs do not need to be modified under the proposed approach. The MLA maintains a QoS class table and a routing table for the network selection procedure and uses the GPRS Tunneling Protocol-Control plane (GTP-C) control messages to execute network switching. In the future, we will measure the throughput of the multi-link network and the switch delay between the heterogeneous radio networks.
A multi-RAT bandwidth aggregation mechanism with software-defined networking
(2016-02)
Yang, Shun-Neng
;
Ho, Shu-Wei
;
Lin, Yi-Bing
;
Gan, Chai-Hien
;
資訊工程學系
The population of smart mobile devices drives the mobile traffic growth rapidly. To deal with the traffic explosion, heterogeneous radio network integration is considered as a cost-effective solution for mobile operators to reduce network congestion. With the coverage overlapping of various wireless networks (e.g., LTE and Wi-Fi), we can use multiple networks to transfer different services simultaneously. In this paper, we integrate the multiple radio access technology (multi-RAT) with software-defined networking (SDN) to make the multi-RAT network more programmable, dynamically manageable and adaptable. The analytic model and performance evaluation show that our mechanism can significantly reduce the response times when the multi-RAT network traffic is unbalanced, where the throughput degradation of adapting our mechanism is 4.15% on average. (C) 2015 Elsevier Ltd. All rights reserved.
A Seamless Multi-Link Switch Solution for LTE and Wi-Fi Integrated Networks
(2013)
Gan, Chai-Hien
;
Lin, Yung-Chun
;
Yang, Shun-Neng
;
Lin, Yi-Bing
;
資訊工程學系
Today, smart mobile devices drive the mobile traffic growth rapidly. The Integration of multiple radio access technologies is a viable solution for mobile operators to fulfill users\' data usage. In this paper, we consider the interwork issue for the LTE and Wi-Fi integration network. Based on the GPRS Tunneling Protocol (GTP), a multi-link switch approach is proposed to solve the seamless handover and cooperating issues between LTE and Wi-Fi networks. The performance results show that the average switch delay is slight, which is efficient to support most of real-time application services, such as VOIP service and interactive games.
An Effective Antenna Allocation for CoMP Transmission in Dense Small Cell Networks
(2016-01-01)
Tseng, Chun-Kai
;
Wu, Sau-Hsuan
;
Chao, Hsi-Lu
;
Liu, Chia-Lung
;
Gan, Chai-Hien
Despite that network capacity can increase with cell densification, interferences from adjacent cells may deteriorate the throughput of users close to cell edges. To alleviate this problem and to offer a service quality with no significant cell edge degradation, we propose a feasible coordinated multi-point (CoMP) transmission architecture from a new look on antenna allocation in dense small cell networks (DSN). The CoMP idea is based on a two-step mechanism; the first step partitions the entire service region into multiple areas, and the second step adjusts the number of active users for each area. We then develop an antenna allocation algorithm to enhance the cell-edge user throughput, making use of the spatial multiplexing (SM) gain, array gain and cooperative diversity gain. Simulation results show that applying SM to DSN plays a crucial role to enhance the user throughput. And one of our proposed cooperative schemes is shown to have a great potential to improve the throughput for a large portion of users or the cell service area.
An Effective Power Conservation Scheme for IEEE 802.11 Wireless Networks
(2009-05-01)
Gan, Chai-Hien
;
Lin, Yi-Bing
;
資訊工程學系
;
Department of Computer Science
In IEEE 802.11 wireless networks, a mobile station (MS) can power down the transceiver to save energy. To achieve power conservation, an access point (AP) periodically broadcasts beacons to notify the associated MSs about their traffic indications, and the MSs periodically wake up to listen to the beacons. The MS awake time scheduling is an important issue, which affects the number of simultaneously awake MSs to compete for access. We propose a power conservation scheme to optimally schedule the awake times among the MSs, such that the number of MSs awaking at the same time is minimal. Our study indicates that the proposed scheme demonstrates good performance in terms of frame loss and delay time.
Charge scheduling of electric vehicles in highways
(2013-06-01)
Yang, Shun-Neng
;
Cheng, Wei-Sheng
;
Hsu, Yu-Ching
;
Gan, Chai-Hien
;
Lin, Yi-Bing
Today, charging stations (CSs) for electric vehicles (EVs) are much less popular than gas stations. Therefore, searching and selecting CSs is an important issue for the drivers of EVs. This paper investigates the EV charging problem. We propose two types of CS-selection algorithms. The first type only utilizes local information of an EV. The second type utilizes the global information obtained through interactions between the EVs and a Global CS-selection (GCS) server through the mobile telecommunications network. Our study indicates that by using the global information (specifically the workload status of each CS), the EVs can be effectively charged with short waiting times at the CSs. (C) 2011 Elsevier Ltd. All rights reserved.
Charge Scheduling of Electric Vehicles in Highways through Mobile Computing
(2011)
Yang, Shun-Neng
;
Cheng, Wei-Sheng
;
Hsu, Yu-Ching
;
Gan, Chai-Hien
;
Lin, Yi-Bing
Today, charging stations (CSs) for electric vehicles (EVs) are much less popular than gas stations. Therefore, searching and selecting CSs is an important issue for the drivers of EVs. This paper investigates the EV charging problem. We propose two types of CS-selection algorithms. The first type only utilizes local information of an EV. The second type utilizes the global information obtained from mobile computing. Specifically, the EVs interact with a Global CS-selection (GCS) server through the mobile telecommunications network. Our study indicates that by using the global information (specifically the workload status of each CS), the EVs can be effectively charged with short waiting times at the CSs.
Design and implementation of UMTS session management in the user equipment
(2007-08-01)
Gan, Chai-Hien
;
Lin, Yi-Bing
;
Chen, Shi-Hi
;
資訊工程學系
;
Department of Computer Science
In universal mobile telecommunications system (UNITS), session management (SM) maintains a communication session between a user equipment (UE) and the core network. 3GPP TS 24.008 specifies the SM functions and the communication protocols between the UE and the core network. However, the interaction between the SM and other entities in the UE are not specified in detail. This paper designs and implements the SM software. We use a finite state machine (FSM) to model the SM functions. Based on the FSM and the primitives, we describe how to set up the development steps to implement the SM at the UE. Copyright (c) 2006 John Wiley & Sons, Ltd.
Effective Service Architecture and Antenna Allocation Mechanism for CoMP Transmissions in Ultra Dense Networks
(2019-09-01)
Tseng, Chun-Kai
;
Wu, Sau-Hsuan
;
Chao, Hsi-Lu
;
Quek, Tony Q. S.
;
Gan, Chai-Hien
A practical and effective service deployment method is proposed for coordinated multi-point (CoMP) transmissions in ultra-dense networks (UDN). Despite the potential of UDN for throughput enhancement, the throughput of edge users is still considerably deteriorated by interferences from adjacent cells. Applying the CoMP transmissions among cells appears to be a feasible solution to resolve this issue. However, the nature of the almost randomly deployed locations of small cell base stations (BSs) and their limited numbers of antennas make it difficult to design an effective resource coordination mechanism for the CoMP services in UDN. Reconsidering this problem from an antenna allocation viewpoint, we present a simple yet effective approach to improve the cell-edge throughput under a centralized radio access network architecture. The first step is to partition the entire service area into multiple subareas, and the second step is to allocate the antenna degrees of freedom to each subarea. To improve the scalability of this service method, a two-tier service deployment method is further introduced based on the BS clustering and service area partitioning of the entire network. The simulation results show that the proposed service architecture can provide a significant improvement on the cell-edge throughput while still maintaining a good average throughput in the UDN.
EFFICIENT ROUTING FOR INTERNATIONAL MOBILE CALL SETUP
(2010-08-01)
Gan, Chai-Hien
;
Tsai, Meng-Hsun
;
Lin, Yi-Bing
;
交大名義發表
;
National Chiao Tung University
Mobile telecommunications operators offer telephone services when the subscribers roam to other countries. However, a call setup to a roaming mobile subscriber may result in two expensive international trunk connections. In this article we propose a plug-in solution to avoid the international trunk connections. By adding public switched telephone network gateways, our solution does not need to modify the existing mobile telecommunications systems. In this solution a timer is defined to reduce the call drop probability. A prediction method is proposed to determine the timeout period such that the call drop probability is limited within an acceptable range. Numerical experiments are conducted to indicate the performance of the prediction method. Finally, a prototype implemented at National Chiao Tung University is described.
Mobile charging information management for smart grid networks
(2013-04-01)
Yang, Shun-Neng
;
Wang, Hsiao-Wei
;
Gan, Chai-Hien
;
Lin, Yi-Bing
;
資訊工程學系
With today's electric charging technology, charging time of an electric vehicle (EV) is much longer than that for a gasoline vehicle, and therefore the queueing effect at an EV charging station (CS) may be serious. That is, when an EV arrives at an overloaded CS, it is likely that the EV will wait for a long time before it is charged. This paper investigates the waiting problem for EV charging. We propose a Mobile CS (MCS) management system to dynamically distribute charging pole support that reduces the waiting times of EVs incurred in a fixed CS. A Mobile Charging Information Management System (MC-IMS) is presented to describe the execution flow of the MCS service. Simulation experiments are conducted to investigate the waiting time performance for the proposed mechanism. Our study indicates that the MCS-based MC-IMS provides effective EV charging with short waiting times. (C) 2012 Elsevier Ltd. All rights reserved.
Mobility management through access network discovery and selection function for load balancing and power saving in software-defined networking environment
(2016-09-02)
Yang, Shun-Neng
;
Ke, Cheng-Hsu
;
Lin, Yi-Bing
;
Gan, Chai-Hien
;
資訊工程學系
The mobile traffic has grown rapidly with the popularity of smart mobile devices. To accommodate increasing traffic, heterogeneous network integration is considered as a viable solution. By overlapping the coverage of heterogeneous networks (e.g., the long-term evolution (LTE) and Wi-Fi integrated network), the mobile operators can use the offloading service (e.g., Wi-Fi offloading) to reduce network congestion. In this approach, a proper network coordination mechanism is required for load balancing of the LTE and Wi-Fi integrated network. In this paper, we use access network discovery and selection function (ANDSF) to suggest selection of proper base stations (e.g., LTE evolved Node Bs or Wi-Fi access points) to user equipment (UE) for load balancing. We integrate the ANDSF with software-defined networking (SDN) to make the ANDSF-aided network more programmable, flexible, and dynamically manageable. Moreover, we propose a power-saving ANDSF (PSA) algorithm to appropriately assign network resource to UEs and reduce the power consumption of Wi-Fi access points (APs). We have implemented the SDN-based PSA and measured the delay times. We also conduct simulation experiments to show that the successful probability of UEs\' resource requests to PSA is almost the same as the proposed schemes of the previous studies when the network traffic is unbalanced. Our study indicates that for unbalanced traffic, PSA can reduce 15.63 % more power consumption of Wi-Fi AP than the previous approaches.
PERFORMANCE MEASUREMENTS OF TD-LTE, WIMAX AND 3G SYSTEMS
(2013-06-01)
Lin, Yi-Bing
;
Lin, Pin-Jen
;
Sung, Yingrong Coral
;
Chen, Yuan-Kai
;
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 Call Routing Cost for Femtocells
(2010-07-01)
Lin, Yi-Bing
;
Gan, Chai-Hien
;
Liang, Ching-Feng
;
資訊工程學系
;
交大工研院聯合研發中心
Femtocell is an effective solution to improve indoor coverage for cellular networks, where short-range and low-power Base Stations (BSs) called Femto BSs are deployed in small areas (e. g., buildings). We propose the Femto Private Branch Exchange (FPBX) to concentrate the traffic of the Femto BSs in a specific area, such as a campus or an enterprise with central or distributed locations. Through the FPBX, a normal cellular call between two Femto users can be replaced by a low-cost extension call. Therefore, the call routing cost can be significantly reduced. In this approach, the existing mobile network nodes are not modified. We analytically analyze the call routing performance for the FPBX approach, and develop simulation experiments to validate against the analytic model. Our study indicates that the FPBX approach can effectively reduces the call setup costs and the voice trunk costs among Femto users by slightly increasing the normal cellular call setup costs.
Resource Allocation with CoMP Transmission in Ultra Dense Cloud-Based LTE Small Cell Networks
(2017-01-01)
Chen, Yu-Han
;
Chao, Hsi-Lu
;
Wu, Sau-Hsuan
;
Gan, Chai-Hien
;
資訊工程學系
Coordinated multipoint (CoMP) transmission has been considered an important technology to manage the serious inter-cell interference in ultra-dense small cell networks (UDN). In this paper, a scheduling framework and a two-tier spectrum resource allocation method for CoMP transmissions in UDNs are proposed. For a number of clusters, the tier-one allocation divides the resource blocks (RBs) into two sets: one is for center users and the other is for edge users. Tier-two resource allocation is performed at a central scheduler to allocate spectrum resources to edge users on a cluster basis. Applying the two-tier scheduling method to a simulated UDN on OpenStack and OpenAirInterface (OAI) software platforms, the UE throughput performances are presented and discussed. We further analyze the computational complexity of each step for performing 1-slot CoMP transmission. The numerical simulation results showed that, upon deploying the small cells in a Poisson Point Process (PPP) with mean density 0.0003/km(2), and the ratio of eNBs to UEs is (3: 1), more than 50% UEs have 15Mbps throughput performance.
Throughput Analysis of LTE and WiFi Heterogeneous Dense Small Cell Networks
(2019-01-01)
Kao, Yi-Hung
;
Chiu, Hsin-Li
;
Wu, Sau-Hsuan
;
Chao, Hsi-Lu
;
Gan, Chai-Hien
The throughput performance of a heterogeneous dense small cell network (HetNet) with collocated WiFi and LTE interfaces is studied herein. From a geometrical statistical viewpoint, the average throughput for LTE with the function of further enhanced inter-cell interference coordination (FeICIC) is investigated in an attempt to find a proper operation setting for FeICIC to benefit users on cell edges. Furthermore, the optimal setting for WiFi offloading is also studied to maximize the worse user experience in such a HetNet. The proposed analysis method allows us to further study a proper strategy that provides fair services to users under the severe interferences in HetNet.
Time-division-based cyclic scheduling for UMTS high-speed downlink shared-channels
(2007-07-01)
Gan, Chai-Hien
;
Perng, Nei-Chiung
;
Lin, Phone
;
Kuo, Tei-Wei
;
資訊工程學系
Third Generation Partnership Project working group proposes the high-speed downlink packet access to speed up downlink transmission for the universal mobile telecommunication system, where the time-division-based high-speed downlink shared-channel (HS-DSCH) approach is adopted. Our previous work proposed the shared-channel assignment and scheduling (SCAS) scheme to efficiently schedule the DSCH to serve different connections, which guarantees the requested transmission rate for each connection. However, limitations exist in the SCAS scheme: 1) the requested transmission rates of connections must be two's power numbers of the basic transmission rate and 2) all served connections should be rescheduled while a new request is. granted, which introduces extra rescheduling overhead to the system. This paper proposes the elastic shared-channel assignment and scheduling (eSCAS) scheme to overcome these limitations. We formally prove the correctness of the eSCAS scheme. An analytical model and simulation experiments are conducted to compare the performance for eSCAS and SCAS. Our study shows that eSCAS can significantly improve the acceptance rate for new connections without increasing the rescheduling overhead.