Browsing by Author "Tseng, CC"

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A batch-update strategy for the distributed HLRs architecture in PCS networks
(2003-05-01)
Hwang, HW
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Tseng, CC
;
Chang, MF
;
資訊工程學系
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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 causal multicast protocol for mobile distributed systems
(2000-12-01)
Chi, KH
;
Yen, LH
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Tseng, CC
;
Huang, TL
;
資訊工程學系
Causal message ordering in the context of group communication ensures that ail the message receivers observe consistent ordering of events affecting a group as a whole. This paper presents a scalable causal multicast protocol for mobile distributed computing systems. In our protocol, only a Dart of the mobility agents in the system is involved in group computations and the resulting size of control information in messages can be kept small. Our protocol can outperform qualitatively the counterparts in terms of communication overhead and hand-off complexity An analytical model is also developed to evaluate our proposal. The performance results show that the proposed protocol is promising.
A direction-based location update scheme with a line-paging strategy for PCS networks
(2000-05-01)
Hwang, HW
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Chang, MF
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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.
A fair protocol for fast resource assignment in wireless PCS networks
(1999)
Wang, TP
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Tseng, CC
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Hwang, SY
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資訊工程學系
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Department of Computer Science
Efficient sharing of communication resources is essential to PCS networks since the wireless bandwidth is limited. The Resource Auction Multiple Access (RAMA) protocol was recently proposed for fast resource assignment and handover in wireless PCS networks. The RAMA protocol assigns available communication resources (e.g., TDMA time slots or frequency channels) to subscribers one at a time using a collision resolution protocol based on subscriber ID's. However, the RAMA protocol encounters an unfairness problem; furthermore, performance results also indicate that it is inefficient at transmitting fixed-length subscriber ID's. Moreover, the emerging services such as teleconferencing have been presenting new challenges to dynamic-priority resource assignment. Tn this paper, we propose a modification to the RAMA protocol to improve its performance and resolve the unfairness problem. The proposed protocol also adopts dynamic priority assignment to improve the QOS for subscribers in overload environments.
A framework for mobile multicast using dynamic route reconstructions
(1999)
Chi, KH
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Tseng, CC
;
Huang, TL
;
交大名義發表
;
資訊工程學系
A mobile computing environment allows hosts to roam while retaining access to the Internet, Multicasting is one of the most important facilities for constructing reliable distributed systems and cooperative applications. Host mobility, however, challenges multicasting in this environment: the established multicast delivery paths may frequently restructure along with host migrations, incurring expensive overheads, This paper presents a framework for network-layer multicasting while keeping a low overhead in adapting multicast routes to mobile host locations. This is achieved by partitioning the mobile environment into non-overlapping regions, so that changes in the multicast routes due to host intra-region movements are hidden from other regions, An analytical model was developed for performance evaluation. It shows that, compared with the best known proposal, our scheme reduces the average multicast latency by more than 66%, while causing less than 7% overhead.
A hierarchical proxy architecture with load-based scheduling scheme to support network mobility
(2003)
Hsu, YY
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Tseng, CC
;
資訊工程學系
;
Department of Computer Science
A mobile router and all its attached nodes constitute a mobile network A mobile network may be deployed in a mass transportation to enable people to access the Internet when traveling. However, people in the mobile network have to share scarce wireless bandwidth, and thus tolerate unreasonable long delay if their requests were not scheduled appropriately, In this paper, we present a hierarchical-proxy architecture and a load-based scheduling scheme to enhance the performance of the mobile networks with two-tier wireless interfaces. The load-based scheduling scheme classifies Internet services into lightweight and heavyweight services according to their response data sizes and allows heavyweight services to be transferred only in the low-tier network With the load-based scheduling scheme, we can prevent heavyweight services from occupying the scarce high-tier bandwidth and hampering the transmission of other lightweight services. Simulation results show that the proposed architecture and scheduling scheme can significantly increase the completion rate and decrease the average waiting time of both lightweight and heavyweight services, and thus can serve more concurrent requests of multi-services in the mobile network.
A new locality-based IP multicasting scheme for mobile hosts
(2001-03-15)
Tseng, CC
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Chi, KH
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Huang, TL
;
資訊工程學系
;
Department of Computer Science
Internet protocol multicasting is a mechanism widely used in the Internet to disseminate information. Multicast delivery paths may need to be frequently restructured along with host migrations, at the expense of nontrivial overhead or multicast latency. This paper presents a scheme with short multicast latency, while retaining acceptable overhead in adapting the delivery paths to mobile host locations. We exploit the locality in host movements and keep active the networks that mobile hosts have most recently visited. As long as hosts migrate within these active networks, multicast delivery paths can remain unchanged upon host movements. Performance results show that, compared with the best known proposal, our scheme is promising. (C) 2001 Elsevier Science B.V. All rights reserved.
An approach to smooth foreign agent handoff
(2002-05-01)
Tseng, CC
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Chi, KH
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Tsai, CH
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資訊工程學系
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Department of Computer Science
For ubiquitous computing and communication, a mobile node needs to change upon movements its network- and link-layer points of attachment to the Internet. Conventionally. the network-layer protocol is unaware of the link-layer changes, so IP datagrams to and from a moving node could be lost. Considerable system performance degradation might therefore result. This paper presents a scheme to integrate the handoff procedures of the two layers in the context of Mobile IP with route optimization. Experiment results show that our scheme is promising and can reduce packet loss due to host migrations substantially.
An intelligent agent-based mobile resource reservation scheme
(2005)
Wang, JT
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Yang, JS
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Tseng, CC
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資訊工程學系
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Department of Computer Science
This paper presents an Intelligent Agent-based Resource reservation aPproach (IARSVP) to support Quality of Service (QoS) aware packet transmissions for mobile networks. Mobile Intelligent Agents (MIAs) are characterized by their ability to move across wide-area networks, operate autonomously on foreign hosts, and perform tasks on behalf of the originating hosts. With MIAs, IARSVP can pre-allocate resources in advance for anticipated location an MN may visit next. Because MIAs carries the MN's W requirement and administration specification, and mobility association together with the necessary executable codes, they can adjust themselves in accordance with the network topology and current resource usage in locating forwarding points for the anticipated locations the MNs may visit next. Therefore, IARSVP can support route optimization and regional registration naturally, avoid redundant resource reservations made in common routes, and discover alternative route dynamically. Furthermore, MIAs can also perform location updates on behalf of MNs. Simulation results show that IARSVP outperforms Mobile RSVP and Hierarchical Mobile RSVP in terms of forced termination, reservation blocking, and session completion probabilirties.
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.
Burst synchronization of slotted random access with preamble power ramping in the reverse link of CDMA systems
(2003-09-01)
Sheen, WH
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Tseng, CC
;
Ho, JS
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電信工程研究所
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Institute of Communications Engineering
Efficient random access is one of the key designs in code-division multiple-access (CDMA) cellular systems. Random access is used by user equipment for initial access, requesting dedicated channels and transmitting short packet data to a base station. In random access, a preamble part is usually devised for fast and reliable burst synchronization, which is essential in order to avoid excessive access delay and/or repeated transmissions that may reduce the overall system capacity. This paper investigates the issue of burst synchronization for the slotted random access with preamble power ramping in the reverse link of CDMA systems. A flexible burst synchronizer based on a parallel-serial code-phase detector is proposed, which can be easily configured to achieve different complexity/performance tradeoffs. A general analysis is also presented with important design parameters being taken into account, including the number of correlators, power control error, power ramping step, diversity order, frequency offset, multipath combining, and others. The analysis is verified by computer simulations.
Design and implementation of an OA&M system for WLL network
(2000-09-01)
Huang, JY
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Tsai, HM
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Lin, YB
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Tseng, CC
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資訊工程學系
This paper describes the design and implementation of an OA&M system for DECT-based WLL network. This system follows the client-server architecture that enables remote management through the Internet, Object-oriented design is used to yield quality software, where the entire WLL network is treated as a hierarchical collection of objects. The "plug-in" mechanism provides the capabilities of replacing and extending OA&M functionalities in run-time, Design patterns are applied to improve the reusability of software components. Two types of user interfaces are implemented in different platforms to provide access to the OA&M system, Although our design is tailored for the WLL network, it is also appropriate to serve as the OA&M system for other small-scale telecommunication systems.
Design and implementation of two-tier Mobile Ad Hoc Networks with seamless roaming and load-balancing routing capability
(2004)
Hsu, YY
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Tseng, YC
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Tseng, CC
;
Huang, CF
;
Fan, JH
Due to its flexibility, Mobile Ad Hoc Network (MANET) has attracted a lot of attention recently. Most existing works, however, limit a MANET as a stand-alone network. In this paper, we propose a two-tier MANET by extending the connectivity of the MANET to the Internet. Some hosts in the MANET are equipped with cellular interfaces and are called gateways, which can provide Internet connections. Such extension would greatly improve the connectivity of MANET To maintain seamless connectivity, we modify the Mobile IP to make traversing private networks (i.e., NAT) of cellular networks possible. We also propose a load-balancing routing protocol to utilize the cellular interfaces of gateways, which are likely to be bottlenecks to the Internet. A prototype is implemented and performance results obtained from the testbed is reported.
Dynamic scheduling framework on an RLC/MAC layer for, general packet radio service
(2003-09-01)
Yang, JS
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Tseng, CC
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Cheng, RG
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資訊工程學系
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Department of Computer Science
In this paper, we present a traffic-scheduling framework that can dynamically allocate radio resources to a general packet radio service (GPRS) mobile station (MS) based on the interference levels of the radio links and the quality of service (QoS) specification of the MS. The underlying,idea of this scheduling scheme is to preserve more bandwidth for use by those MSs that are within a low interference region so that the limited radio resources can be used more effectively. In this scheme, an MS uses a low transmission rate for data transfer when the MS is within a high interference region to avoid wasting bandwidth by transmitting data in a condition with high interference. In order to compensate for the service loss of the MS, we will allocate more bandwidth to the MS when it is within a low interference region. In addition, we also propose an analytical model that can be used to derive the transmission rate for an MS in a low interference region based on the delay-bound requirement of the MS. The performance results show that our dynamic scheme can utilize the bandwidth more effectively to satisfy various QoS requirements of the MSs in the GPRS system without changing the convolution-coding rate.
Dynamic scheduling framework on RLC/MAC layer for general packet radio service
(2001)
Yang, JS
;
Tseng, CC
;
Cheng, RG
;
資訊工程學系
;
Department of Computer Science
In this paper, we present a traffic-scheduling framework which can dynamically allocate radio resource to GPRS handsets based on the interference levels of the radio links. Essentially, when a mobile station (MS) is within a high interference region, the proposed scheme uses a low transmission rate to reduce bandwidth wastage due to re-transmissions. On the other hand, when the MS is within a low interference region, a high transmission rare is used, in order to fulfill its quality of service (QoS) requirements. One of our contributions is to derive a rate decision analytical model to determine the high and low transmission rates based on the interference conditions and the delay-bound requirement. The performance results show that our dynamic scheme can effectively utilize the bandwidth to satisfy various QoS requirements in the GPRS system without changing the convolution-coding rate.
HLR replication protocols for global mobility management in PCS networks
(2003-01-01)
Lee, GC
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Wang, TP
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Tseng, CC
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資訊工程學系
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Department of Computer Science
The new trend for PCS networks is to provide mobile users with large-scale mobile capability across many service areas. In this scenario, global database management for PCS networks has become an increasingly important research issue. In this paper, we examined two replicated database strategies, single-replica (SR) and multiple-replica (MR), for large-scale mobility of per-user data management in personal communication networks. The SR strategy uses a single replica approach of HLR. The MR strategy replicates the per-user data of HLR in many regions. The two strategies are based a partial replication scheme, and a primary copy method is used to maintain replicas' consistency. Our numerical results show that the MR strategy outperforms the SR strategy in most situations; however, it may be worse when the probability of a mobile user visiting a foreign region is high and the query rates from other foreign regions are low. Additionally, the number of replicas should be compact in the MR strategy in order to achieve a reasonable query response time. Therefore, we propose an adaptive multiple replication protocol to choose a suitable replication strategy and to decide the optimized number of replicas.
HMRSVP: A hierarchical mobile RSVP protocol
(2003)
Tseng, CC
;
Lee, GC
;
Liu, RS
;
Wang, TP
;
資訊工程學系
In this paper, we propose a hierarchical Mobile RSVP (HMRSVP) that can achieve mobility independent QoS-guaranteed services in mobile computing environments. The HMRSVP integrates RSVP with Mobile IP regional registration and makes advance resource reservations only when an inter-region movement may possibly occur. We first show that, by NS simulator, our HMRSVP can achieve the same QoS guarantees as MRSVP does with fewer resource reservations. Then, we show that HMRSVP outperforms MRSVP in terms of reservation blocking, forced termination and session completion probabilities.
HMRSVP: A hierarchical Mobile RSVP Protocol
(2001-01-01)
Tseng, CC
;
Lee, GC
;
Liu, RS
;
資訊工程學系
;
Department of Computer Science
In this paper we propose a hierarchical Mobile RSVP (HMRSVP) that can achieve mobility, independent QoS guaranteed services in mobile computing environments. The HMRSVP integrates RSVP with Mobile IP regional registration and makes advance resource reservations only when an inter-region movement may possibly happen. We first show that, by NS simulation, our HMRSVP can achieve the same QoS guarantees as MRSVP with fewer resource reservations. Then, we show that HMRSVP outperforms MRSVP in terms of reservation blocking, forced termination and session completion probabilities.
HMRSVP: A hierarchical Mobile RSVP Protocol
(2001-01-01)
Tseng, CC
;
Lee, GC
;
Liu, RS
In this paper we propose a hierarchical Mobile RSVP (HMRSVP) that can achieve mobility, independent QoS guaranteed services in mobile computing environments. The HMRSVP integrates RSVP with Mobile IP regional registration and makes advance resource reservations only when an inter-region movement may possibly happen. We first show that, by NS simulation, our HMRSVP can achieve the same QoS guarantees as MRSVP with fewer resource reservations. Then, we show that HMRSVP outperforms MRSVP in terms of reservation blocking, forced termination and session completion probabilities.
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.