Browsing by Author "Cheng, Ray-Guang"

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A Dynamic Load-Balancing Scheme for Heterogeneous Wireless Networks
(2014)
Tsao, Shiao-Li
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Wang, Chen-Wei
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Lin, Yun-Ciou
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Cheng, Ray-Guang
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資訊工程學系
Current heterogeneous wireless networks often overlap because of their complementary characteristics and the large deployment of various wireless access technologies. Mobile devices, which are equipped with multiple wireless interfaces, called multiple radio access technologies (multi-RATs) mobile stations (MSs), are also becoming increasingly popular. Therefore, common radio resource management (CRRM) has been proposed to coordinate heterogeneous radio resource allocations and improve the resource utilization of heterogeneous wireless networks. However, CRRM is an NP-hard problem, and low-complexity approaches for dynamic resource management are in high demand. In this paper, the resource request and allocation between multi-RAT MSs and heterogeneous wireless networks are modeled as a directed graph. Thus, the problem of searching for feasible radio resource allocations is simplified to finding trees in a directed graph. Based on the proposed model, a heuristic scheme can be used to find a feasible solution efficiently, and dynamically adjust the workload of heterogeneous BSs to accommodate new requests. Experimental results demonstrate that the heuristic scheme can reduce the request reject rate by 10%-55% compared with conventional approaches.
A Predictive Intelligent Traffic Controller for Broadband Multimedia IP Networks
(2008)
Lin, Li-Fong
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Chang, Chung-Ju
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Cheng, Ray-Guang
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電信工程研究所
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Institute of Communications Engineering
The paper proposes a predictive intelligent traffic controller for broadband multimedia IP networks with quality-of-service (QoS) provisioning. The predictive intelligent traffic controller considers a user's requested traffic characteristics, QoS requirements, and predicted system performance measures to determine its connection admission. A pipelined recurrent neural network with extended recursive least square learning algorithm (PRNN/ERLS) is employed to predict the system congestion status and the packet loss probability of the broadband multimedia systems. The PRNN/ERLS possesses an infinite memory of previous signals and appropriately weights them to precisely capture the correlation among signals of these performance measures; and thus the effect on the congestion status and packet loss probability can be well captured and even estimated in advance. Simulation results show that the proposed predictive intelligent traffic controller can achieve higher system utilization than the conventional non-predictive intelligent traffic controller by about 5.6% at light-to-heavy traffic transient periods.
Design and Implementation of a Skype Protocol Analyzer
(2013)
Cheng, Ray-Guang
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Tsai, Po-Yao
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Lin, Ping-Chen
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Lian, Chia-Liang
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Liu, Tse-Han
Proprietary protocols on the Internet often pose challenges for users and analysts to determine how secure the applications are or how easy private information can be accessed. This work presents a tool that processes packets generated by Skype and analyzes its proprietary implementation. The goal of the exercise is to determine how one may reverse engineer a proprietary protocol and obtain private information. The results demonstrate that a buddy-list of a target user can be obtained through the developed Skype Protocol Analyzer.
Iterative Contending-user Estimation Method for OFDMA Wireless Networks with Bursty Arrivals
(2013-01-01)
Cheng, Ray-Guang
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Wei, Chia-Hung
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Tsao, Shiao-Li
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資訊工程學系
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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.
Maximum freedom last scheduling algorithm for downlinks of DSRC networks
(2007-06-01)
Chang, Chung-Ju
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Cheng, Ray-Guang
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Shih, Hao-Tang
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Chen, Yih-Shen
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電信工程研究所
This paper proposes a maximum freedom last (MFL) scheduling algorithm for downlinks, from the roadside unit to the onboard unit (OBU), of dedicated short-range communication networks in intelligent transportation systems, to minimize the system handoff rate under the maximum tolerable delay constraint. The MFL scheduling algorithm schedules the service ordering of OBUs according to their degree of freedom, which is determined by factors such as remaining dwell time of service channel, remaining transmission time, queueing delay, and maximum tolerable delay. The algorithm gives the smallest chance of service to the OBU with the largest remaining dwell time, the smallest remaining transmission time, and the largest weighting factor, which is a function of the queueing delay and the maximum tolerable delay. Simulation results show that the MFL scheduling algorithm outperforms the traditional first-come-first-serve and earliest-deadline-first methods in terms of service failure and system handoff rates.
Method for power-efficient transmission supporting integrated services over wireless local area network
(2006-11-16)
Shih, Chih-Yung
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Cheng, Ray-Guang
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Chang, Chung-Ju
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Chen, Yih-Shen
This invention provides a method for power-efficient transmission supporting integrated service over WLAN. The said invention combines the polling-based and the contention-based mechanisms, named on-demand polling (ODP). In the ODP scheme, a voice station is in the polling list when it is in the active mode. During the idle mode, it is configured to operate in the sleep mode for saving power. Also, it adopts the contention-based mechanism to join the list again while returning from the idle mode. On the other hand, the data station adopts the contention-based mechanism to transmit its packets over WLAN. In addition, to achieve service differentiation, the said invention also employs a prioritized access probability for voice over data services. Simulation results show that the said invention can reduce the power consumption for voice stations and enhance the throughput for data stations.
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
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Tsao, Shiao-Li
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資訊工程學系
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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
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Cheng, Ray-Guang
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Tsao, Shiao-Li
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資訊工程學系
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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
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Wei, Chia-Hung
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Tsao, Shiao-Li
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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.
The SA-based Group Handoff Scheme for Heterogeneous Wireless Networks in M2M Communications
(2015)
Pul, Heng-Hao
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Chang, Chung-Ju
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Cheng, Ray-Guang
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電機學院
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College of Electrical and Computer Engineering
A group of multi-mode wearable devices or mobile terminals (MTs) may be carried by the same vehicle and then perform group handover during the movement within heterogeneous networks. However, it is a challenging work to determine a proper target network which is good for both MTs and the network provider. This paper presents a simulated-annealing-based group handover decision scheme to reduce the group handover blocking ratio, decrease the number of handover, balance the traffic load between networks, and ensure the target quality of service (QoS) requirements of MTs. Simulation results show that the proposed scheme can reduce the group handover blocking ratio efficiently and balance the load. Besides, when the number of group MTs is not quite large, the number of handover can be reduced and the QoS requirements can be fulfilled.