Browsing by Author "Hwang, HW"

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A batch-update strategy for the distributed HLRs architecture in PCS networks
(2003-05-01)
Hwang, HW
;
Tseng, CC
;
Chang, MF
;
資訊工程學系
;
Department of Computer Science
Owing to the increasing population of mobile subscribers, the rapidly expanding signaling traffic has become a challenge to the mobility management in PCS networks. Multiple database schemes to reduce signal traffic and to solve the bottleneck problem of the single home location register (HLR) architecture have been proposed by many researchers. However, in most of the multiple location databases or HLR systems, extra signaling is required for the multiple database updates. We propose a batch-update strategy, instead of the immediate update method, for the location-tracking schemes with replication to reduce the signaling overhead. In this paper, we first introduce a distributed HLRs architecture in which each HLR is associated with a localized set of VLRs and the location registrations and queries are processed locally. Then we propose our batch-update strategy and present two pointing schemes for inter-HLR call deliveries. The numerical result shows that our approach can effectively decrease the signaling cost of location registration and call delivery compared with the IS-41 standard. Copyright (C) 2002 John Wiley Sons, Ltd.
A direction-based location update scheme with a line-paging strategy for PCS networks
(2000-05-01)
Hwang, HW
;
Chang, MF
;
Tseng, CC
;
資訊工程學系
;
Department of Computer Science
On the problem of location update and terminal paging, many schemes using ring-paging strategies have been proposed, However, sequentially paging the rings surrounding the mobile user's last updated location may cause large paging cost. In this letter, we propose a direction-based location update (DBLU) scheme using a line-paging strategy to reduce the paging cost. A moving direction identification mechanism using only simple computations detects the change of moving direction and updates the mobile's location. The numerical results show that our DBLU scheme achieves good performance when the paging cost is high.
Analysis of the direction-based location update schemes for wireless cellular networks
(2002)
Hwang, HW
;
Tseng, CC
;
Chang, MF
;
資訊工程學系
;
Department of Computer Science
In the paper, we first compare the performance of the direction-based location update (DBLL) schemes with that of the distance-based location update scheme under various mobility behaviors of the mobile hosts (MTs). The comparison results show that under the random walk model, the base DBLU scheme outperforms the distance-based location update scheme when the mobility to caff ratios (MCRs) of the MTs are low. However, it has been shown that the MTs are likely to possess forward-prone movement characteristics in micro-cellular architectures. If the MTs am indeed prone to make forward movements, the base DBLU scheme will he better than the distance-based location update scheme in all the MCRs according to our analysis. Therefore we further propose two enhanced DBLU schemes, namely the forward direction-based location update (FDBLU) and the restricted forward direction-based location update (RFDBLU) schemes, for the location tracking of the MTs m micro-cellular architectures. Analytical results also show that both FDBLU and RFDBLU schemes outperform the base DBLU scheme, and RFDBLU scheme is the best among the direction-based location update schemes.