Browsing by Author "Chia, Chung-Yung"

Now showing 1 - 6 of 6

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.
Channel allocation for priority packets in the GPRS network
(2006-08-01)
Chia, Chung-Yung
;
Chang, Ming-Feng
;
資訊工程學系
;
Department of Computer Science
As the General Packet Radio Service (GPRS) network begins to provide such as "push-to-talk" (PTT) service, delay-sensitive packets should be given higher priority in transmission. In this paper, we study two channel allocation schemes that implement priority queues for priority packets in the GPRS network: Bitmap Channel Allocation (BCA) and Uplink State Flag Channel Allocation (USFCA). Our study shows that the transmission delay of priority packets in the GPRS network can be better guaranteed using USFCA.
DEPLOYMENT OF THE FIRST COMMERCIAL LWA SERVICE
(2017-12-01)
Tu, Yuan-Kuang
;
Lee, Cheng-Hua
;
Liu, Chia-Horng
;
Chia, Chung-Yung
;
Chen, Yuan-Kai
This column reports the deployment of the first commercial LWA service. The deployed LWA network reuses and is merged with the existing individual LTE and WLAN networks. Our experience indicates that this approach allows quick establishment of LWA service, which nicely resolves the coexistence problems arising from deploying the LTE system in unlicensed spectrums. Specifically, in the initial stage, selected LWA hotspots with the required service were built in two months. Through this deployment, we show how Chunghwa Telecom utilizes unlicensed spectrum to open up additional capacity to support LTE service. Specifically, the throughput of an LWA site can be more than twice of that for an LTE eNB. Also, through an LWA eNB, an LWA-capable user equipment can indirectly perform seamless handover between a Wi-Fi AP without mobility capability and a standard eNB. This indirect handover time is less than 400 ms plus the standard EAP-SIM authentication time for Wi-Fi.
Flat-Rate Packet Scheduling for the WCDMA Systems with HSDPA
(2010)
Chia, Chung-Yung
;
Chang, Ming-Feng
;
資訊工程學系
;
Department of Computer Science
To attract more users to use mobile packet services, mobile operators have begun to provide flat-rate packet services in the WCDMA system with High Speed Downlink Packet Access (HSDPA). Since usage does not incur extra cost, flat-rate users may always stay on line and occupy most of the radio channel resources. In this paper, we consider a HSDPA network serving two types of user packets: charged packets (CPs) and flat-rate packets (FRPs). We consider the balance between serving the FRPs and CPs. Four downlink packet scheduling methods were studied in this paper. Our study using Markov process shows that Dynamic Discard Timer for FRPs and Dynamic Guard Slots for CPs methods are more effective in transmitting downlink CPs especially when the downlink FRP traffic is high. Therefore, they are better in guaranteeing the system throughput for CPs, and thus the operator revenue can be better protected.
The frequency of CFVD speed report for highway traffic
(2015-04-10)
Chang, Ming-Feng
;
Chen, Chi-Hua
;
Lin, Yi-Bing
;
Chia, Chung-Yung
;
資訊工程學系
The control signals of cellular networks have been used to infer the traffic conditions of the road network. In particular, consecutive handover events are being used to estimate the traffic speed. During traffic congestion, consecutive handover events may be rare because vehicles move slowly, and thus very few or no speed reports would be generated from the congested area.However, the traffic speed report rate during traffic congestion has not been investigated in the literature. In this paper, we present an analytic model to estimate the speed report rate from cellular network signaling in steady traffic conditions, that is, the traffic speed and flow are assumed constant. Real field trial data were used to validate our analytic model. In addition, computer simulations were conducted to study how speed reports are generated in dynamic traffic conditions when traffic speed and flow change rapidly. Our study indicates that in a typical cell of length 1.5km with a typical expected call holding time of 1min, no speed report was generated from a congested three-lane highway. Our study demonstrates that the lack of speed reports from consecutive handover events during rush hours indicates severe traffic congestion, and new methods that can estimate traffic speed from cellular network data during severe traffic congestion need to be developed. Copyright (c) 2013 John Wiley & Sons, Ltd.
Uplink Connection Scheduling for Flat-Rate Data Services in the UMTS Network
(2009-06-01)
Chia, Chung-Yung
;
Chang, Ming-Feng
;
資訊工程學系
;
Department of Computer Science
To attract more users to mobile packet services, universal mobile telecommunication system (UMTS) operators have been prompting flat-rate packet services. Since usage does not incur cost, flat-rate users tend to stay online longer and occupy most of the radio channel resources. We consider a UNITS network serving two types of user connections: normal user connections (NUCs) and flat-rate user connections (FRUCs). Our goal is to maximize the revenue of the operator by giving a priority to NUCs over FRUCs without discontenting the flat-rate users, in order not to lose the flat-rate users to other operators. Uplink FRUCs may be asked to subrate or suspend transmission when the radio network is fully utilized. Four combinations of scheduling techniques, including queueing, guard channels (GCs), preemption, and rate adaptation, have been studied, and analytic models using Markov processes were used to evaluate their performances. We proposed a cost function representing the revenue loss due to both blocked NUCs and lost flat-rate users. The system parameters used in our analysis are based on realistic operation data. Our analytic results indicate that the revenue loss can be minimized by using waiting queues (WQs) and preemption. Rate adaptation is ineffective in minimizing the revenue loss because subrated connections are less efficient in using the radio spectrum. GCs for NUCs are unnecessary when a WQ or preemption is used. This paper may be valuable for UMTS operators in serving flat-rate users.