Browsing by Author "Sue, KL"

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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.
N-class replacement policy for resolving mobility database overflow
(2003)
Sue, KL
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Lo, CC
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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.
One-step pointer forwarding strategy for location tracking in distributed HLR environment
(1997-10-01)
Sue, KL
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Tseng, CC
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資訊工程學系
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Department of Computer Science
One of the main challenges in personal communication service (PCS) is to locate many mobiles that may move frequently from place to place. Such a system operation is called location tracking, Many network signals flow, and database queries are required to achieve such a task. In addition to the two-level hierarchical strategy in IS-41 and GSM, several strategies have been proposed to improve the efficiency of location tracking, Pointer forwarding was used to reduce the expensive home location register (HLR) accesses, Previously, the distributed HLR scheme was proposed to prevent HLR from becoming a bottleneck in the signaling network, However, the length of a forwarding pointer chain may be lengthened in a distributed HLR environment, In this paper, we propose a more efficient strategy to overcome this potential problem, This strategy attempts to migrate the locating chains in a distributed HLR system when a mobile issues a registration operation, As a consequence, the length of any forwarding pointer chain does not exceed one in our strategy, Simulation results indicate that our strategy significantly decreases the locating cost, In fact, this strategy provides an upper bound of location tracking time owing to the fact that the length of any locating path does not exceed one. Furthermore, obsolete entries in local databases visiter location registers can be reclaimed in this strategy.
Overflow control in mobile communication using N-class replacement
(2003-01-23)
Sue, KL
;
Lo, CC
;
資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
A strategy called N-class replacement (NR) policy is proposed to overcome visitor location register (VLR) overflow in a mobile communication system. The NR policy requires only few bits in the VLR record. It is feasible for separated VLR databases in real mobile networks. For the rate of excellent replacement, the simulation results show that the NR policy outperforms currently proposed policies.
Second chance replacement policy for mobile database overflow
(2002)
Lo, CC
;
Sue, KL
;
資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
The visitor location register (VLR) is used to store temporary records for roaming users. Due to the limited capacity, the VLR may be full. This phenomenon is called VLR overflow. By replacing an existing record, the incoming user can still receive services. The most-idle replacement (MR) policy was proposed to improve the random replacement (RR) policy. The MR policy is almost the optimum method and outperforms RR policy significantly. However, the MR policy requires global information to find the most-idle user. It needs considerable extra cost and is unfeasible due to the separated VLR databases in the real mobile network. Therefore, we propose the second chance replacement (SCR) policy to overcome these drawbacks. The SCR policy needs only an additional bit in the record. Partial information is sufficient for our method, so it is feasible in the real mobile network. Moreover, the simulation results show that the SCR policy outperforms the MR policy in most scenarios investigated in our study.