Browsing by Author "Yang, SR"

Now showing 1 - 5 of 5

A mobility management strategy for GPRS
(2003-11-01)
Lin, YB
;
Yang, SR
;
資訊工程學系
;
Department of Computer Science
In general packet radio service (GPRS), a mobile station (MS) is tracked at the cell level during packet transmission, and is tracked at the routing-area (RA) level when no packet is delivered. A READY timer (RT) mechanism was proposed in 3GPP 23.060 to determine when to switch from cell tracking to RA tracking. In this mechanism, a threshold interval T is defined. If no packet is delivered within T, the MS is tracked at the RA level. When a packet arrives, the MS is tracked at the cell level again. However, the RT mechanism has a major fallacy in that the RTs in both the MS and the serving GPRS support node may lose synchronization. This paper considers another mechanism called READY counter (RC) to resolve this problem. In this approach, a threshold K is used. Like the RT approach, the MS is tracked at the cell level during packet transmission. If no packets are delivered after the MS has made K cell crossings, the MS is tracked at the RA level. We also devise an adaptive algorithm called dynamic RC (DRC). This algorithm dynamically adjusts the K value to reduce the location update and paging costs. We propose analytic and simulation models to investigate RC, RT, and DRC. Our study indicates that RC may outperform RT. We also show that DRC nicely captures the traffic-mobility patterns and always adjusts the K threshold close to the optimal values.
A mobility management strategy for UMTS
(2003)
Yang, SR
;
Lin, YB
;
資訊工程學系
;
Department of Computer Science
Universal Mobile Telecommunications System (UMTS) utilizes a three-level location management strategy to reduce the net costs of location update and paging in the packet-switched service domain. Within a communication session, a mobile station (MS) is tracked at the cell level during packet transmission. In the idle period of an ongoing session, the MS is tracked at the UTRAN registration area (URA) level to avoid frequent cell updates while still keeping the radio connection. If the MS is not in any communication session, the MS is tracked at the routing area (RA) level. The inactivity counter mechanism was proposed in 3GPP 25.331 to determine when to switch between the three location tracking modes. In this mechanism, two inactivity counters are used to count the numbers of cell updates and URA updates in an idle period between two packet transmissions. If the number of cell updates reaches a threshold K-1, the MS is switched from the cell tracking to the URA tracking. After that, if the number of URA updates reaches a threshold K-2, the MS is tracked at the RA level. This paper proposes simulation model to investigate the performance of the inactivity counter mechanism. Our study provides guidelines for K-1 and K-2 selection to achieve lower net costs of location update and paging.
Modeling UMTS discontinuous reception mechanism
(2005-01-01)
Yang, SR
;
Lin, YB
;
資訊工程學系
;
Department of Computer Science
This paper investigates the discontinuous reception (DRX) mechanism of universal mobile telecommunications system (UNITS). DRX is exercised between the network and a mobile station (MS) to save the power of the MS. The DRX mechanism is controlled by two parameters: the inactivity timer threshold and the DRX cycle. Analytic and simulation models are proposed to study the effects of these two parameters on output measures including the expected queue length, the expected packet waiting time, and the power saving factor. Our study quantitatively shows how to select appropriate inactivity timer and DRX cycle values for various traffic patterns.
Performance evaluation of location management in UMTS
(2003-11-01)
Yang, SR
;
Lin, YB
;
資訊工程學系
;
Department of Computer Science
The universal mobile telecommunications system utilizes a three-level location-management strategy to reduce the net costs of location update and paging in the packet-switched service domain. Within a communication session, a mobile station (MS) is tracked at the cell level during packet transmission. In the idle period of an ongoing, session, the MS is tracked at the UTRAN registration area (URA) level to avoid frequent cell updates while still keeping the radio connection. If the MS is not in any communication session, the MS is tracked at the routing-area (RA) level. The inactivity counter mechanism was proposed in 3GPP 25.331 to determine when to switch between the three location-tracking modes. In this mechanism, two inactivity counters are used to count the numbers of cell and URA updates in an idle period between two packet transmissions. If the number of cell updates reaches a threshold K-1, the MS is switched from cell tracking to URA tracking. After that, if the number of URA updates reaches a threshold K-2, the MS is tracked at the RA level. This paper proposes analytical and simulation models to investigate the performance of the inactivity counter mechanism. Our study provides guidelines for K-1 and K-2 selection to achieve lower net costs of location update and paging.
Resolving mobile database overflow with most idle replacement
(2001-10-01)
Hung, HN
;
Lin, YB
;
Peng, NF
;
Yang, SR
;
統計學研究所
In a personal communications service (PCS) network, mobility databases called visitor location registers (VLRs) are utilized to temporarily store the subscription data and the location information for the roaming users. Because of user mobility, it is possible that the VLR is full when a mobile user arrives. Under such a circumstance, the incoming user has no VLR record and thus cannot receive PCS services. This issue is called VLR overflow. To resolve the VLR overflow problem, a VLR record can be selected for replacement when the VLR is full and then the reclaimed storage is used to hold the record of the requesting user. This paper considers the most idle replacement policy to provide services to mobile users without VLR records. In this policy, the record with the longest idle time is selected for replacement. We propose an analytic model to investigate the performance of this replacement policy. The analytic results are validated against simulation experiments. The results indicate that our approach effectively resolves the VLR overflow problem.