Network Performance Analysis and Improvement:

• Performance Modeling of Mobile Telecommunications Networks with Overlapping Location Area Configuration
• In this work, we have described four LA selection policies and proposed an analytic model to study the performance of these LA selection policies. Our study provides guidelines to determine appropriate degree of overlapping among the LAs.


• 主要成就與成果之績效評述
• 學術或技術成就之評述
• Previous work assumed that at each movement, the MS moves to any of its neighboring cells with the same probability. Moreover, previous studies mainly investigated central LA selection algorithm. Our work described four LA selection policies and proposed an analytic model to study the performance of these LA selection policies.

• Modeling UMTS Power Saving based on M/G/1 Queue with Vacations
• We investigated the power saving mechanism of UMTS. UMTS 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 tI and the DRX cycle tD. Queueing analytic and simulation models were proposed to study the effects of tI and tD on output measures including the expected queue length, the expected packet waiting time, and the power saving factor.


• 主要成就與成果之績效評述
• 學術或技術成就之評述
• To the best of our knowledge, our work is the first one to model UMTS power saving mechanism by using M/G/1 queue with vacations.

• Selecting the Optimal UMTS Power Saving Parameters
• Based on our queueing model, we proposed analytic analysis and simulation model to study the optimal tI and tD selections that maximize the MS power saving under the given mean packet waiting time constraint. We also devised an adaptive algorithm called dynamic DRX (DDRX). This algorithm dynamically adjusts the tI and tD values to enhance the performance of UMTS DRX.


• 主要成就與成果之績效評述
• 學術或技術成就之評述
• Our study quantitatively showed how to select the best inactivity timer and DRX cycle values for various traffic patterns. We also showed that DDRX nicely captures the user traffic patterns, and always adjusts the tI and tD close to the optimal values.

• Modeling UMTS Power Saving with Bursty Packet Data Traffic
• In this work, we proposed a novel semi-Markov process to model the UMTS DRX with bursty packet data traffic. The analytic results were validated against simulation experiments. We investigated the effects of the two DRX parameters on output measures including the power saving factor Ps and the mean packet waiting time E[tw].


• 主要成就與成果之績效評述
• 學術或技術成就之評述
• In the literature, analytic and simulation models have been developed to study the UMTS power saving performance mainly for Poisson traffic. To accommodate bursty packet data traffic, our work proposes a novel semi-Markov process to model the UMTS power saving with WWW-like traffic source.

• Modeling Power Saving for WLAN and UMTS Interworking
• 3GPP 43.318 specifies the GAN for interworking between WLAN and UMTS core network. A dual-mode MS is equipped with two communication modules to support both WLAN and UMTS radio technologies, which shortens the battery lifetime of the MS. We have proposed an analytical model and conducted simulation experiments to study the power consumption of WLAN-UMTS dual-mode MSs.


• 主要成就與成果之績效評述
• 學術或技術成就之評述
• Previous works considered the power saving mechanisms for WLAN and UMTS separately. Our work proposes an analytic model and conducts simulation experiments to study the power consumption of WLAN-UMTS dual-mode MSs.