Browsing by Author "Lu, Fang-Sun"

Now showing 1 - 2 of 2

A callback mechanism for Private Telecommunications Networks
(2010-03-15)
Chang, Ming-Feng
;
Lu, Fang-Sun
;
Chia, Chung-Yung
;
資訊工程學系
;
Department of Computer Science
Private Telecommunications Networks (PTNs), such as enterprise telephony and Voice over IP (VoIP), have been widely deployed. A common limitation of PTNs is that PTN users are usually not assigned with Public Switched Telephone Network (PSTN) EA 64 numbers. A PTN user is usually identified by an extension number or a URI (universal resource identifier). When a PTN user initiates a call to a PSTN user, it is not possible to use the PTN calling party's identifier as the caller ID; instead, an E.164 number of the PBX or VoIP gateway is used. As a result, the PSTN called party cannot use the caller ID received to call back to the PTN calling party later, if the PTN user's extension number or URI is unknown. This paper proposes a callback table approach to solve this problem. We describe how the call-out information is stored into and retrieved from a callback table maintained in the PBXs; or VoIP gateways to provide callback service. Numeric analysis has been performed to evaluate the performance of this callback solution. The numeric results indicate that the callback method provides a satisfactory solution when there is sufficient voice traffic served by a VoIP gateway. (C) 2009 Elsevier B.V. All rights reserved.
Performance modeling of integrated mobile prepaid services
(2007-03-01)
Yang, Wei-Zu
;
Lu, Fang-Sun
;
Chang, Ming-Feng
;
資訊工程學系
;
Department of Computer Science
Prepaid personal communication service users have outnumbered postpaid users. This paper studies the charging issues of an integrated Global System for Mobile Communications (GSM) and General Packet Radio Service (GPRS) prepaid service, where a single prepaid account provides a user both voice and data services. The call setup and charging procedures for GSM and GPRS are presented using the Customized Applications for Mobile network Enhanced Logic network architecture. To reduce the probability of terminating both ongoing voice and data calls, we suggest that no new call be admitted when the user credit is below a threshold. An analytic model has been developed to evaluate the performance of the approach. Computer simulations have also been used to verify the results. The numeric results indicate that the force-termination probability can be significantly reduced by choosing an appropriate threshold of the user credit.