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收集所有交通大學研究人員與學生個人或團體所發表之各項學術著作，涵蓋期刊論文、教師專書、學位論文等項。;;Collections of Publications of NCTU Researchers and Students Like Journal Papers and Thesis.

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Now showing 1 - 8 of 8
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    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.
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    Reducing location update cost in a PCS network
    (1997-02-01)
    Lin, YB
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    資訊工程學系
    ;
    Department of Computer Science
    Location tracking operations in a personal communications services (PCS's) network are expensive. Several strategies have been proposed to reduce the location update cost, This paper studies a special case of a location tracking algorithm called the alternative location algorithm, This special case is referred to as the two location algorithm (TLA), An analytical model is proposed to compare the performance of TLA and the IS-41 protocol. Our study indicates that the performance of TLA is significantly affected by the user moving patterns and the call traffic. If the user mobility is higher than the call frequency or the user tends to move back to the previously visited registration areas, then TLA may significantly outperform IS-41, We also observe that the variance of the portable residence times in registration areas has impact on the performance of TLA (i.e., better performance is expected for larger variance).
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    Adaptive algorithms for reducing PCS network authentication traffic
    (1997-08-01)
    Lin, YB
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    Mohan, S
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    Sollenberger, N
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    Sherry, H
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    資訊工程學系
    Two authentication schemes (AS's) ha ce been proposed in the Electronic Industry Association/Telecommunications Industry Association's (EIA/TIA) Telecommunications Systems Bulletins (TSB's) 51 for incorporation in the cellular industry Interim Standard IS 41 Revision C. In the first scheme, which we refer to as the RS scheme, a unique secret key [also known as shared secret data (SSD)] is Shared only between the authentication center (AC) and handset. In the second scheme, referred to as the S scheme, the SSD is also shared with the visited system. The performance of the two schemes can be compared by using the expected number of call originations/terminations between two consecutive registrations or call-to-mobility ratio (CMR). Based on the message flow (accesses to databases), it is apparent that the S scheme outperforms the WS schemes if the CMR ratio is large. The CMR's of users will likely span a wide range and, even for the same user, will perhaps vary from time to time. It is therefore desirable to switch between the AS's based on the users' CMR to reduce the signaling network traffic. We propose two adaptive algorithms to determine how and when to switch between the AS's for a given user. Our performance study indicates that as the CMR of a user changes, the adaptive algorithms automatically select the best AS in real time.
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    Mobility Management for Low-Latency Handover in SDN-Based Enterprise Networks
    (2016)
    Chen, Ce
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    Lin, Yu-Ting
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    Yen, Li-Hsing
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    Chan, Min-Cheng
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    Tseng, Chien-Chao
    Low-latency handover is crucial to real-time traffic in wireless networks. This paper considers an enterprise network managed by emerging Software Defined Network (SDN) technology. For this networking environment, we propose a mobility management scheme named Mobility SDN (M-SDN) that reduces the traffic pause time caused by a host-initiated layer-2 handover. M-SDN performs handover preparation in parallel with the layer-2 handover that involves N-casting of active flows to every potential handover target. Handover preparation is enabled by efficient address resolution and location tracking. We have implemented a prototype of M-SDN and conducted several experiments to evaluate the performance of M-SDN. Experimental results show that M-SDN effectively reduces the impact of layer-2 handovers without any modification on mobile devices.
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    Resetting forwarding pointers with delay propagation schemes in a distributed HLR environment
    (2001-04-01)
    Lee, GC
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    Wang, TP
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    Tseng, CC
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    資訊工程學系
    ;
    Department of Computer Science
    In this paper, we propose a new location tracking method for pointer forwarding with distributed HLRs schemes to decrease the location tracking cost. Similar to the distributed HLR schemes, the location information is replicated on all HLRs in our scheme. However, unlike the traditional distributed HLR schemes, we propagate the most recent location changes from an HLR to reset the forwarding pointers in other HLRs, and thus reduce the cost of location tracking for call deliveries. The signaling cost of location propagation may be too costly to be practical. Therefore, we allow some inconsistency to exist among the location data of HLRs and defer the propagation of location changes to reduce the propagation cost. Three delay propagation policies are also proposed and analyzed using simulation. The performance result shows that the delay propagation policies reduce the propagation cost and the propagation resetting process degrades the location tracking cost. Our method preserves a low total cost for call deliveries, registrations and propagations in distributed HLRs.
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    Diminishing capacity requirement for mobility database in wireless ATM
    (2004-04-01)
    Sue, KL
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    Lo, CC
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    資訊管理與財務金融系 註：原資管所+財金所
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    Department of Information Management and Finance
    In wireless ATM, Visitor Location Register (VLR) is the database that supports mobility management. In case the number of roaming users exceeds the VLR supports, the arriving users cannot receive any service. To solve the problem, the Random Replacement (RR) policy randomly selects a victim record in VLR to be replaced with the record of the arriving user. The quality of services for the victim user will certainly drop. Therefore, the proportion of affected users is not allowed to exceed a tolerable threshold. Apparently, VLR size is the key factor of the threshold. The cost for maintaining a VLR increases significantly as its size grows. So, how to utilize the capacity efficiently is an important issue in VLR planning. We propose a Second Chance Replacement (SCR.) policy to reduce the requirements for VLR capacity. As compared with the RR policy, the discrete-event simulation results show that the SCR policy can save 2.5% to 28% VLR size under various QoS thresholds.
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    N-class replacement policy for resolving mobility database overflow
    (2003)
    Sue, KL
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    Lo, CC
    ;
    交大名義發表
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    National Chiao Tung University
    Visitor Location Register (VLR) may overflow due to the limited capacity. By replacing an existing record, the overflow users can still receive services. The most-idle replacement (MR) policy was proposed to improve the performance or the random replacement (RR) policy. The MR policy seems to he optimum and outperforms the RR policy significantly. However, the MR policy has potential limitations. Accordingly, we propose the N-class replacement (NR) policy to overcome the drawbacks. Moreover, the simulation results show that the NR policy outperforms the MR policy in most scenarios investigated in our study. As N increases, the improvement becomes more considerable.
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    Improving channel scanning procedures for WLAN handoffs
    (2007)
    Tsao, Shiao-Li
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    Cheng, Ya-Lien
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    資訊工程學系
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    Department of Computer Science
    WLAN has been widely deployed over public and private areas and has become one of popular access technologies for mobile Internet services in recent several years. Handoff between WLAN access points (APs) that introduce packet loss and delay is one of the critical issues for mobile Internet applications, especially for real-time communications. Previous studies indicated that channel scanning time contributes a significant portion of handoff latency and introduces packet loss and delay. Therefore, solutions based on active scan were proposed to reduce total scanning time of channels so that the service disruption of a communication can be minimized. The other solutions based on passive scan scattering scans between packets did not optimize the total scanning time but avoid packet loss and delay. However, solutions for channel scanning procedures which combine active and passive scan strategies and take total scan latency, packet loss, and delay together into consideration have not yet been investigated. In this paper, a generic channel scanning model is proposed and solutions to improve scanning procedures for WLAN handoff are presented. Simulation results demonstrate that the proposed approaches achieve faster scan time than the existing solutions without violating packet delay and loss requirements specified by the applications during WLAN handoff. Moreover, the implementation of the proposed mechanisms on a WLAN SoC (System-on-Chip) is also discussed in this paper.