Browsing by Author "Wei, Chia-Hung"

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Iterative Contending-user Estimation Method for OFDMA Wireless Networks with Bursty Arrivals
(2013-01-01)
Cheng, Ray-Guang
;
Wei, Chia-Hung
;
Tsao, Shiao-Li
;
資訊工程學系
;
Department of Computer Science
Random access channels (RACHs) in cellular networks are normally designed for Poisson-distributed arrivals with a constant rate. Unexpected bursty arrivals may result in severely collisions in RACHs and thus, degrade users\' service qualities. This paper presents an analytical model to investigate the transient behavior of the RACHs with bursty arrivals generated in a specific time interval in OFDMA wireless networks. The proposed model considers the effect of new arrivals and the real-world implementation constraints of the OFDMA random access procedure such as periodic access characteristic, uniform random backoff policy, and power-ramping effect. The average number of contending and success mobile stations (MSs) in each random-access slot are then derived using the proposed model. The accuracy of the proposed model was verified through computer simulations and the results show the accuracy of the analysis.
Modeling and Estimation of One-Shot Random Access for Finite-User Multichannel Slotted ALOHA Systems
(2012-08-01)
Wei, Chia-Hung
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Cheng, Ray-Guang
;
Tsao, Shiao-Li
;
資訊工程學系
;
Department of Computer Science
This paper presents a combinatorial model and approximation formulas to estimate the average number of successful and collided users for a one-shot random access in finite-user multichannel slotted ALOHA systems. The proposed model and approximation can be used to evaluate the performance of group paging for machine-type communication (MTC) in 3GPP LTE. Numerical results demonstrate the applicable range of the approximation formulas and the accuracy of the derived performance metrics.
Performance Analysis of Group Paging for Machine-Type Communications in LTE Networks
(2013-09-01)
Wei, Chia-Hung
;
Cheng, Ray-Guang
;
Tsao, Shiao-Li
;
資訊工程學系
;
Department of Computer Science
Machine-type communication (MTC) is a crucial service for next-generation cellular networks. Mass access to the network byMTC devices may result in the overload of radio access networks (RANs) and degrade the service quality of human-to-human communication. Group paging is one of the mechanisms proposed to alleviate the RAN-overload problem. This paper presents an analytical model based on a recursive contending-users estimation (RCE) method proposed in the literature to derive the performance metrics of collision probability, access success probability, average access delay, statistics of preamble transmissions, statistics of access delay, and utilization of random-access opportunities (RAOs) for group paging with various combinations of group sizes and reserved radio resources in a paging access interval. The optimal group size and required RAOs are subsequently derived based on the given target access success probability. Numerical results demonstrate that the proposed model can accurately estimate the performance of group paging.
RACH Collision Probability for Machine-type Communications
(2012)
Cheng, Ray-Guang
;
Wei, Chia-Hung
;
Tsao, Shiao-Li
;
Ren, Fang-Ching
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資訊工程學系
This paper summarizes the two definitions of the collision probability from the perspective of an MTC device and an RAO were presented in 3GPP TR 37.868. We use the results presented in TR 37.868 to show the inconsistency between the two definitions. It worth to note that the researcher needs to clearly specify the definition they used in presenting the results of their proposed radio access network overload control schemes. This paper further presents an analytical model to derive the collision probability, the success probability, and the idle probability based on the two definitions.