Browsing by Author "Chlamtac, I"

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An adaptive measured-based preassignment scheme with connection-level QoS support for mobile networks
(2002-07-01)
Luo, XY
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Li, B
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Thng, ILJ
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Lin, YB
;
Chlamtac, I
This paper presents a new adaptive bandwidth allocation scheme to prevent handoff failure in wireless cellular networks, known as the measurement-based preassignment (MPr) technique. This technique is particularly useful in micro/pico cellular networks which offers quality-of-service (QoS) guarantee against call dropping: The proposed MPr scheme distinguishes itself from the well-known guarded channel (GC) based schemes in that it allows the handoff calls to utilize a prereserved channel. pool before competing for the shared channels with new call arrivals. The key advantage of the proposed MPr scheme is that it enables easy derivation of the number of channels that needs to be reserved for handoff based on a predetermined handoff dropping probability, without the need for solving the often complex Markov chain required in GC schemes; thus, making the proposed MPr scheme-simple and efficient for implementation. This is essential in handling multiple traffic types with potentially different QoS requirements. In addition, the MPr scheme is adaptive in that it can dynamically adjust the number of reserved channels for the handoff according to the periodical measurement of the traffic status within a local cell; thus completely eliminating the signaling overhead for status information exchange among cells mandated in most existing channel allocation schemes. Numerical results and comparisons are given to illustrate the tradeoff.
An all-IP approach for UMTS third-generation mobile networks
(2002-09-01)
Lin, YB
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Pang, AC
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Haung, YR
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Chlamtac, I
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交大名義發表
This article describes the UMTS all-IP approach for third-generation mobile systems, with emphasis on the core network architecture. Followng the introduction of the core network nodes, we elaborate on application-level registration, circuit-switched call origination, packet-switched call origination, and packet-switched call termination.
Billing strategies and performance analysis for PCS networks
(1999-03-01)
Fang, YG
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Chlamtac, I
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Lin, YB
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資訊工程學系
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Department of Computer Science
It is predicted that by the year 2000, U.S, cellular carriers will invest billions of dollars for cellular billing and customer care. Two of the most desirable attributes of the cellular billing systems are the flexibility of upgrade and ability to inform the billing experts quickly about the status of the system to minimize any possible fraud and improve customer service. Although the second attribute can be realized by reporting the billing customer record in real time, this tends to congest the signaling channel, which is not desirable, In this paper, we propose several schemes for the provision of a quick billing status report which maintains low-signaling traffic. The performance of these schemes is derived analytically. We expect that these results may pro,ide a guideline for the future design of on-line billing systems in personal communication ser,ices (PCS's) networks.
Call performance for a PCS network
(1997-10-01)
Fang, YG
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Chlamtac, I
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Lin, YB
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資訊工程學系
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Department of Computer Science
It is well known that, due to the mobility of a portable and limited channel availability, calls of portables may not be completed due to being blocked or terminated during the call initiation or the handover process, The characteristics of the call-completion and call holding times for both a complete call and an incomplete call are of critical importance for establishing the actual billing process in the PCS network. In this paper, we derive the call-completion probability (hence, call-dropping probability) and the effective call-holding time distributions for complete/incomplete calls with a general cell-residence time and a general call-holding time are analyzed, and. general computable formulas are obtained, We show that when fall-holding times are Erlang distributed, easy-to-compute formulas for the probability of a call completion and the expected effective call-holding times for both a complete call and an incomplete call can be derived.
Call performance for a PCS network
(1997-10-01)
Fang, YG
;
Chlamtac, I
;
Lin, YB
;
資訊工程學系
;
Department of Computer Science
It is well known that, due to the mobility of a portable and limited channel availability, calls of portables may not be completed due to being blocked or terminated during the call initiation or the handover process, The characteristics of the call-completion and call holding times for both a complete call and an incomplete call are of critical importance for establishing the actual billing process in the PCS network. In this paper, we derive the call-completion probability (hence, call-dropping probability) and the effective call-holding time distributions for complete/incomplete calls with a general cell-residence time and a general call-holding time are analyzed, and. general computable formulas are obtained, We show that when fall-holding times are Erlang distributed, easy-to-compute formulas for the probability of a call completion and the expected effective call-holding times for both a complete call and an incomplete call can be derived.
Channel occupancy times and handoff rate for mobile computing and PCS networks
(1998-06-01)
Fang, YG
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Chlamtac, I
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Lin, YB
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資訊工程學系
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Department of Computer Science
This paper presents a study of channel occupancy times and handoff rate for mobile computing in MC (Mobile Computing) and PCS (Personal Communications Services) networks, using general operational assumptions. It is shown that, for exponentially distributed call holding times, a distribution more appropriate for conventional voice telephony, the channel occupancy times are exponentially distributed if and only if the cell residence times are exponentially distributed. It is further shown that the merged traffic from new calls and handoff calls is Poisson ii and only if the cell residence times are exponentially distributed, too. When cell residence times follow a general distribution, a more appropriate way to model mobile computing sessions, new formulae for channel occupancy time distributions are obtained. Moreover, when the call holding times and the cell residence times have general (nonlattice) distributions, general formulae for computing the handoff rate during a call connection and handoff call arrival rate to a cell are given. Our analysis illustrates why the exponential assumption for call holding time results in the underestimation of handoff rate, which then leads to the actual blocking probabilities being higher than the blocking probabilities for MC/PCS networks designed using the exponential distribution approximation for call holding time. The analytical results presented in this paper can be expected to play a significant role in teletraffic analysis and system design for MC/PCS networks.
Dynamic periodic location area update in mobile networks
(2002-11-01)
Lin, YB
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Lee, PC
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Chlamtac, I
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資訊工程學系
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Department of Computer Science
In mobile communications networks, periodic location area update (PLAU) is utilized to detect the presence of a mobile station (MS). In 3GPP Technical Specifications 23.012 and 24.008, a fixed PLAU scheme was proposed for the Universal Mobile Telecommunications System (UNITS), where the interval between two PLAUs is of fixed length. We observe that MS presence can also be detected through call activities and normal location area update (NLAU). Therefore, we propose a dynamic PLAU scheme where the PLAU interval is dynamically adjusted based on the call traffic and NLAU rate. An analytic model is developed to investigate the performance of dynamic and fixed PLAU schemes. This paper provides guidelines to select parameters for dynamic PLAU.
Effects of Erlang call holding times on PCS call completion
(1997)
Lin, YB
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Chlamtac, I
;
交大名義發表
;
資訊工程學系
;
National Chiao Tung University
Previous performance studies of PCS channel allocation assumed that call holding times have an exponential distribution. The exponential call holding time assumption is justified for existing cellular systems, where wireless calls are charged based on the length of the call holding time. Future PCS systems may exercise flat rate billing, and consequently a more general distribution is desirable to model the call holding times. This paper models the call holding times by the Erlang distribution (a generalization of the exponential distribution) to investigate the effect of the variance of the call holding times on the call completion probability. Our analysis indicates that the call completion probability decreases as the variance of the call holding times decreases. This effect becomes more pronounced as the variance of the cell residence times decreases.
Effects of Erlang call holding times on PCS call completion
(1999-05-01)
Lin, YB
;
Chlamtac, I
;
資訊工程學系
;
Department of Computer Science
This paper studies personal communications services (PCS's) channel allocation assuming the Erlang call holding time distribution (a generalization of the exponential distribution) to investigate the effect of the variance of the call holding times on the call completion probability. Our analysis indicates that the call completion probability decreases as the variance of the call holding times decreases, This effect becomes more pronounced as the variance of the cell residence times decreases.
Large effective call holding times for a PCS network
(1996)
Lin, YB
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Chlamtac, I
;
交大名義發表
;
資訊工程學系
;
National Chiao Tung University
This paper addresses two important PCS cost and performance issues: (I) Are blocking probabilities (for new call blocking, forced termination, or call completion) appropriate for PCS network performance measurement? (2) Should PCS service provider offer discount to phone calls that are forced terminated? In order to do that we derive the effective call holding time distributions for complete/incomplete calls by using an analytic model. We assume that the cell residence times have a general distribution so that the measured data from the field trials, after a second order approximation, can be used to drive our model. Our study on the effective call holding time distributions indicates that (1) blocking probabilities do not provide sufficient information to evaluate the performance of a PCS network, and that output measures, such as expected effective call holding times for complete/incomplete calls, are desirable; (2) for a PCS network with moderate user mobility, the service provider can offer substantial discounts to incomplete calls (to increase the user satisfaction) without significantly reducing the profit margin. A quantitative analysis is also provided that can be used to determine the discount factor.
Mobile computing: When mobility meets computation - Guest editor's introduction
(1997-03-01)
Chlamtac, I
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Lin, YB
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資訊工程學系
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Department of Computer Science
Mobile computing: When mobility meets computation - Guest editor's introduction
(1997-03-01)
Chlamtac, I
;
Lin, YB
;
資訊工程學系
;
Department of Computer Science
Mobile number portability
(2003-09-01)
Lin, YB
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Chlamtac, I
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Yu, HC
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科技管理研究所
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Institute of Management of Technology
Mobile number portability allows a mobile subscriber to switch operators without chaning his/her phone number. This article describes and analyzes mobile number portability routing mechanisms and their implementation costs. We first describe the Signaling Relay Function (SRF)-based solution for call related and non-call related routing. Then we describe the Intelligent Network (IN)-based solution for call related routing. Cost recovery issues for number portability are discussed in this article from a technical perspective. We note that rules for cost recovery also depend on business and regulatory factors that vary from country to country.
Modeling frame synchronization for UMTS high-speed downlink packet access
(2003-01-01)
Lin, P
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Lin, YB
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Chlamtac, I
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資訊工程學系
;
Department of Computer Science
Third Generation Partnership Project (3GPP) specification TR 25.950 proposed High-Speed Downlink Packet Access for the Universal Mobile Telecommunication System (UNITS). In this mechanism, an active set of cells is defined for every User Equipment (UE) communication session. The cell with the best wireless link quality (called the serving cell) in the active set is selected for communication with the UE. When the wireless link quality of the old serving cell degrades below some threshold, a new serving cell in the active set is selected to continue the communication session. Our previous work proposed a High-Speed Downlink Packet Access (HSDPA) overflow control scheme with four frame synchronization algorithms to switch the serving cell, and formally proved the correctness of the scheme. In this paper, we propose an analytic model to investigate the performance of these frame synchronization algorithms, and show how the user movement patterns affect the control message delivery costs of these algorithms.
Modeling PCS networks under general call holding time and cell residence time distributions
(1997-12-01)
Fang, YG
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Chlamtac, I
;
Lin, YB
;
資訊工程學系
;
Department of Computer Science
In a personal communication service (PCS) network, the call completion probability and the effective call holding times for both complete and incomplete calls are central parameters in the network cost/performance evaluation, These quantities will depend on the distributions of call holding times and cell residence times, The classical assumptions made in the past that call holding times and cell residence times are exponentially distributed are not appropriate for the emerging PCS networks, This paper presents some systematic results on the probability of call completion and the effective call holding time distributions for complete and incomplete calls with general cell residence times and call holding times distributed with various distributions such as Gamma, Erlang, hyperexponential, hyper-Erlaug, and other staged distributions, These results provide a set of alternatives for PCS network modeling, which can be chosen to accommodate the measured data from PCS field trials, The application of these results in billing rate planning is also discussed.
Module count-based overflow-control scheme for UMTS high-speed downlink packet access
(2004-03-01)
Lin, P
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Lin, YB
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Chlamtac, I
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資訊工程學系
;
Department of Computer Science
In the universal mobile telecommunication system, the user equipment (UE) communicates with all cells in the active set through the air interface; Multiple radio links between the UE and the cells may reduce the transmission speed due to interference. In high-speed downlink packet access (HSDPA), only one serving cell is selected in the active set for high-speed downlink transmission. When the radio link quality between the serving cell and the UE degrades below some threshold, the best cell (in terms of the radio characteristics) in the active set is selected as the new serving cell and the UE switches from the old serving cell to the new serving cell. This action is referred to as frame synchronization. The frame-synchronization information may be delivered through more than one wireless transmission, which introduces long delay for the frame-synchronization process. In this paper, we propose an overflow-control scheme with module count for HSDPA, which guarantees that the frame-synchronization information is delivered through one wireless transmission and that when the UE switches wireless link to the new serving cell, no packet frames are lost.
Overflow control for UMTS high-speed downlink packet access
(2004-03-01)
Lin, PN
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Lin, YB
;
Chlamtac, I
;
資訊工程學系
;
Department of Computer Science
This paper proposes overflow control schemes to support high-speed downlink packet access (HSDPA) mechanism in the universal mobile telecommunication system (UNITS). To access the UNITS services, a user equipment (UE) communicates with all cells. (base stations) in an active set. However, multiple links between the UE and the cells in the active set may reduce the transmission speed due to interference. Third-Generation Partnership Project specification TR 25.950 proposes HSDPA. In this mechanism, the UE only selects one cell (referred to as the serving cell) in the active set for high-speed downlink transmission. In HSDPA, the radio network controller sends the packet frames to the cells in the active set. For the serving cell, the packet frames are forwarded to the UE. On the other hand, every nonserving cell in the active set queues the packet frames in a buffer. If the link quality between the serving cell and the UE degrades below some threshold, the UE selects the best cell in the active set as the new serving cell. Since the nonserving cells do not send packet frames to the UE, their buffers may overflow. In this paper, we propose schemes to address the buffer overflow issue. Our schemes guarantee that when the buffer of a nonserving cell is full, the previously received packet frames in the buffer can be safely dropped, and after the UE has switched wireless link to the new serving cell, no packet frames are lost.
Portable movement modeling for PCS networks
(2000-07-01)
Fang, YG
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Chlamtac, I
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Lin, YB
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資訊工程學系
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Department of Computer Science
In this paper, we propose a nem model for the portable movement in personal communications services (PCSs) networks. Based on this model with general interservice time and registration area residence time distributions, analytic expression for the probability that a portable mores across K registration areas (RAs) is obtained. Busy-line effect on this quantity is also studied and analytic expression is presented, The result given in this paper is very useful for the cost analysis for location updating and paging.