Browsing by Author "Chung, Wen-Ching"

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A Cognitive Priority-based Resource Management Scheme for Cognitive Femtocells in LTE Systems
(2013-01-01)
Chung, Wen-Ching
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Chang, Chung-Ju
;
Ye, Chang-Cing
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電機資訊學士班
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Undergraduate Honors Program of Electrical Engineering and Computer Science
In this paper, we propose a cognitive priority-based resource management (CPRM) scheme for cognitive femtocells in LTE systems with multimedia traffic. Assume that the femtocell adopts cognitive radio technology and serves both macro and femto users. The CPRM scheme dynamically adjusts the sensing duration of each subchannel to enhance the accuracy of channel sensing. According to sensing information, it chooses the unoccupied subchannels as data channels. In order to maximize system throughput and guarantee quality-of-service requirements, the CPRM scheme assigns a suitable priority value and the minimum number of transmission bits to each user based on its traffic type and urgency degree. Simulation results show that, the CPRM scheme can enhance the throughput of femto users by 10.2% and 22.4% as compared to the DBRM [7] and CRRM [8] schemes, respectively, without decreasing the throughput of macro users.
A feedback linearization design for the control of vehicle's lateral dynamics
(2006)
Liaw, Der-Cherng
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Chung, Wen-Ching
;
Song, Chau-Chung
;
Hsieh, Chien-Shu
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電控工程研究所
In this paper, the feedback linearization scheme is applied to the control of vehicle's lateral dynamics. Based on the assumption of constant driving speed, a second-order nonlinear lateral dynamical model is adopted for controller design. It was observed in Liaw and Chung (2006) that the saddle-node bifurcation would appear in vehicle dynamics with respect to the variation of the front wheel steering angle, which might result in spin and/or system instability. Feedback linearization control laws are proposed in this paper to stabilize the vehicle's dynamics at bifurcation points. Numerical simulations for an example model demonstrate the effectiveness of the analytical results.
A Green Radio Resource Allocation Scheme for LTE-A CoMP Systems with Multimedia Traffic
(2013)
Chung, Wen-Ching
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Chang, Chung-Ju
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Huang, Chin-Ya
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Teng, Hsin-Ying
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電機資訊學士班
In this paper, we propose a green radio resource allocation (GRRA) scheme for LTE-A downlink systems with coordinated multi-point (CoMP) transmission to support multimedia traffic. It is a crucial issue to find a balance between throughput maximization and transmission power minimization, especially when the QoS requirement guarantee for multimedia traffic is considered. The GRRA scheme defines a green radio utility function by considering required transmission power, assigned modulation order, and coordinated transmission nodes. Based on this utility function, it coordinates transmission nodes to deliver data on suitable subchannels with suitable transmission power. Simulation results show that, the GRRA scheme can save the transmission power by 33.9% and 40.1%, as compared to the adaptive radio resource allocation scheme [5] with CoMP and the utility-based radio resource allocation scheme [6] with CoMP, respectively. Besides, it enhances the system throughput by 5.5% and improves the Jain fairness index for best effort users by 155% over these two schemes.
A green radio resource allocation scheme for LTE-A downlink systems with CoMP transmission
(2014-08-01)
Chung, Wen-Ching
;
Chang, Chung-Ju
;
Teng, Hsin-Ying
;
電機工程學系
;
Department of Electrical and Computer Engineering
In this paper, we propose a green radio resource allocation (GRRA) scheme for LTE-advanced downlink systems with coordinated multi-point (CoMP) transmission to support multimedia traffic. The GRRA scheme defines a green radio utility function, which is composed of the required transmission power, assigned modulation order, and the number of coordinated transmission nodes. By maximizing this utility function, the GRRA scheme can effectively save transmission power, enhance spectrum efficiency, and guarantee quality-of-service requirements. The simulation results show that when the traffic load intensity is greater than 0.7, the GRRA scheme can save transmission power by more than 33.9 and 40.1 %, as compared with the conventional adaptive radio resource allocation (ARRA) scheme (Tsai et al. in IEEE Trans Wireless Commun 7(5):1734-1743, 2008) with CoMP and the utility-based radio resource allocation (URRA) scheme (Katoozian et al. in IEEE Trans Wireless Commun 8(1):66-71, 2009) with CoMP, respectively. Besides, it enhances the system throughput by approximately 5.5 % and improves Jain's fairness index for best effort users by more than 155 % over these two ARRA and URRA schemes.
A green radio resource allocation scheme for LTE-A downlink systems with CoMP transmission
(2014-08-01)
Chung, Wen-Ching
;
Chang, Chung-Ju
;
Teng, Hsin-Ying
;
電機資訊學士班
;
Undergraduate Honors Program of Electrical Engineering and Computer Science
In this paper, we propose a green radio resource allocation (GRRA) scheme for LTE-advanced downlink systems with coordinated multi-point (CoMP) transmission to support multimedia traffic. The GRRA scheme defines a green radio utility function, which is composed of the required transmission power, assigned modulation order, and the number of coordinated transmission nodes. By maximizing this utility function, the GRRA scheme can effectively save transmission power, enhance spectrum efficiency, and guarantee quality-of-service requirements. The simulation results show that when the traffic load intensity is greater than 0.7, the GRRA scheme can save transmission power by more than 33.9 and 40.1 %, as compared with the conventional adaptive radio resource allocation (ARRA) scheme (Tsai et al. in IEEE Trans Wireless Commun 7(5):1734-1743, 2008) with CoMP and the utility-based radio resource allocation (URRA) scheme (Katoozian et al. in IEEE Trans Wireless Commun 8(1):66-71, 2009) with CoMP, respectively. Besides, it enhances the system throughput by approximately 5.5 % and improves Jain\'s fairness index for best effort users by more than 155 % over these two ARRA and URRA schemes.
A low-complexity beamforming-based scheduling to downlink OFDMA/SDMA systems with multimedia traffic
(2011-04-01)
Chung, Wen-Ching
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Wang, Li-Chun
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Chang, Chung-Ju
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電機工程學系
;
Department of Electrical and Computer Engineering
In this paper, we propose a low-complexity beamforming-based scheduling scheme utilizing a semi-orthogonal user selection (SUS) algorithm in downlink orthogonal frequency division multiple access (OFDMA)/space division multiple access (SDMA) systems to support multimedia traffic. One of the challenges in the multidimensional (space, time, and frequency) radio resource allocation problem for OFDMA/SDMA systems is its high complexity, especially to simultaneously satisfy the quality of services (QoS) requirements for various traffic classes. In the literature, the SUS algorithm is usually applied to the single-class traffic environment, but extending the SUS algorithm to the multimedia environment is not straightforward because of the need to prioritize the real-time (RT) users and the non-real-time (NRT) users. To solve this problem, we propose the concept of urgency value to guarantee the fairness of the NRT as well as the best effort (BE) users while satisfying the delay requirement for the RT users. Simulation results show that, when traffic load is greater than 0.5, the proposed scheduling algorithm can improve the fairness performance by more than 100% over the most recently proposed algorithms.
A Multi-Factors Cell Selection Scheme for Heterogeneous Networks with Multimedia Traffic
(2013)
Chung, Wen-Ching
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Chang, Chung-Ju
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Hsieh, Chih-Yuan
;
Chen, Yung-Han
;
電機資訊學士班
In this paper, we propose a multi-factors cell selection (MFCS) scheme for heterogeneous networks with multimedia traffic. In heterogeneous networks, it is an important issue to determine a suitable access network for call request to support seamless service and highspeed connectivity. The MFCS scheme first chooses candidate cells for call request to satisfy the received signal strength constraint, cell loading constraint, and dwell time constraint. It then determines a target cell from candidate cells based on the QoS factor, loading factor, and mobility factor. Simulation results show that, the MFCS scheme reduces the handoff occurring ratio by 25.5 % and improves the overall system throughput by 15.9 % as compared to the utility and game-theory based network selection (UGNS) scheme [6].
A Wavelength Assignment and Traffic Control Scheme in Reservation Slotted OBS Rings
(2011)
Tang, Wen-Shiang
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Hsieh, Yao-Ting
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Chang, Chung-Ju
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Chung, Wen-Ching
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電子工程學系及電子研究所
In this paper, we design a slotted OBS ring with a proposed reservation signaling protocol. Also, the slotted OBS ring is designed with a wavelength assignment and traffic control (WATOR) scheme to achieve high bandwidth utilization, fairness, and stability. The WATOR scheme adopts a reservation mechanism to avoid burst collisions in the slotted OBS ring system which employs no transit buffers in each node for the reason of bypassing the traffic directly. It is sophisticatedly composed of a wavelength assigner to effectively allocate the ingress data bursts (DBs) with a wavelength and a traffic controller to determine a proper advertised fair rate. The TC further contains a local fair rate generator (LFRG) and an advertised fair rate generator (AFRG). The former generates a local fair rate not only to satisfy the ring ingress aggregated with spatial reuse (RIAS) fairness but also to diminish the effect of the propagation delay; and the latter decides the advertised fair rate referring to the local fair rate generated by the former. Simulation results show that the WA achieves system utilization higher than a group scheduling (GS) scheme [11] by about 5%, and the TC can stabilize all flows much better than but DBA [12].
An Intelligent HARQ Scheme for HSDPA
(2011-05-01)
Huang, Chiao-Yin
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Chung, Wen-Ching
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Chang, Chung-Ju
;
Ren, Fang-Ching
;
電機工程學系
In this paper, we propose an intelligent hybrid automatic repeat request (iHARQ) scheme for high-speed downlink packet access (HSDPA) systems. The challenge in the hybrid automatic repeat request (HARQ) control problem of HSDPA is how to choose an appropriate modulation and coding scheme (MCS) for initial transmission in the situation wherein the channel quality indication (CQI) has report delay. The iHARQ scheme will determine the suitable MCS to maximize the system throughput and guarantee the block error rate requirement in such an uncertain environment. By modeling the HARQ behavior as a Markov decision process, we adopt fuzzy logics to determine an appropriate MCS for each initial packet transmission. In addition, a Q-learning algorithm is utilized to update the fuzzy rule base, according to well-designed reinforcement signals fed back from the HSDPA system, such that the iHARQ scheme can adapt to the delayed CQI. Simulation results show that, compared with a conventional adaptive threshold selection method, the proposed iHARQ scheme increases the system throughput by up to 75.2%.
An Intelligent Priority Resource Allocation Scheme for LTE-A Downlink Systems
(2012-06)
Chung, Wen-Ching
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Chang, Chung-Ju
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Wang, Li-Chun
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電機學院
;
College of Electrical and Computer Engineering
In this paper, we propose an intelligent priority resource allocation (iPRA) scheme for long term evolution-advanced (LTE-A) downlink systems with multimedia traffic. The iPRA scheme intelligently computes priorities for users by using fuzzy inference system so as to enhance system throughput and attain high Jain fairness index while guarantee QoS requirements. Simulation results show that the iPRA scheme can achieve higher system throughput and better QoS requirement guarantee than conventional radio resource allocation schemes in high traffic load, while attains a rather large Jain fairness index.
An MIMO Configuration Mode and MCS Level Selection Scheme by Fuzzy Q-Learning for HSPA(+) Systems
(2012-07-01)
Chung, Wen-Ching
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Chang, Chung-Ju
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Feng, Kai-Ten
;
Chen, Ying-Yu
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電機工程學系
In this paper, we propose a fuzzy Q-learning-based MIMO configuration mode and MCS level (FQL-MOMS) selection scheme for high speed packet access evolution (HSPA(+)) systems. The FQL-MOMS selection scheme intends to enhance the system throughput under the block error rate (BLER) requirement guarantee. It will determine an appropriate MIMO configuration mode and MCS (modulation and coding scheme) level for packet data transmission in HSPA(+) systems, under the situations that the channel status is varying and the channel quality indication (CQI) has report delay. The FQL-MOMS scheme considers not only the reported CQI and the last transmission result but also the BLER performance metric and the transmission efficiency. Moreover, it is effectively configured, where the fuzzy rules and the reinforcement signals for the Q-learning algorithm are sophisticatedly designed. Simulation results show that the proposed FQL-MOMS scheme increases the system throughput by up to 49.3 and 35.9 percent, compared to the conventional adaptive threshold selection (ATS) scheme [12] and the Q-HARQ scheme [14], respectively, under the BLER requirement fulfillment.
Ant Colony-based Radio Resource Allocation for LTE-A Systems with MIMO and CoMP Transmission
(2013)
Chung, Wen-Ching
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Chen, Chien-Yuan
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Huang, Chin-Ya
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Chang, Chung-Ju
;
Ren, Frank
In this paper, we propose an ant colony-based radio resource allocation (ACRA) scheme for LTE-A downlink systems to support multi-input-multi-output (MIMO) and coordinated multi-point (CoMP) transmission. One of the challenges in the radio resource allocation problem for LTE-A systems with MIMO and CoMP transmission is its high complexity. The ACRA scheme first assigns users to direct transmission bandwidth (DTB) zone or CoMP transmission bandwidth (CTB) zone. In the DTB zone, the data is delivered by only one transmission node; while in the CTB zone, the transmission is carried out among multiple transmission nodes. By using ant colony optimization, the ACRA scheme determines one best allocation solution from multiple possible solutions. Simulation results show that, the ACRA scheme enhances the system throughput by 8.8 % as compared to the dynamic interference avoidance scheme [10].
Channel Prediction at the Destination for Relay Training Overhead Reduction in Cooperative Wireless Networks
(2012)
Chung, Wen-Ching
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Wu, Jwo-Yuh
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Gau, Rung-Hung
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Chang, Chung-Ju
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電機工程學系
Signaling overhead reduction has been a key approach to realizing energy-efficient wireless cooperative communication systems. Motivated by the fact that consecutive temporal samples of real-world wireless channels are typically correlated, this paper proposes to exploit such time-domain correlation for relay training overhead reduction in cooperative networks. Specifically, we consider a cooperative transmit beamforming system, in which relay terminals employing the decode-and-forward protocol collaboratively transmit the source message according to the pre maximal-ratio-combining (pre-MRC) principle. During the training phase, the relays send training signals to aid channel estimation at the destination. Based on the acquired record of the channel state information (CSI), the destination then employs a linear minimum-mean-square-errors (LMMSE) channel predictor to update the CSI; in this way, training overhead dedicated by relays can then be reduced. We derive a closed-form expression for the receive SNR at the destination when the pre-MRC beamforming factors are computed in accordance with the predicted CSI. Our analytic results can be used for characterizing the performance degradation of channel prediction as the duration of the prediction phase is enlarged. The proposed analytic studies are corroborated by numerical simulations.
Control design for longitudinal flight dynamics
(2006)
Liaw, Der-Cherng
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Chung, Wen-Ching
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Hsieh, Chien-Shu
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電控工程研究所
;
Institute of Electrical and Control Engineering
In this paper, the control issues of longitudinal flight dynamics is presented. System controllability with respect to the variation of the elevator deflection angle is first discussed Stabilization controllers using washout filter-aided feedback control law is then proposed Case study for F-8 aircraft is explicitly derived for constructing a feasible set of controllers. Numerical simulations for bifurcation scenarios are also given to compare the performance of the designs.
Fuzzy Q-Learning-based Hybrid ARQ for High Speed Downlink Packet Access
(2009)
Huang, Chiao-Yin
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Chung, Wen-Ching
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Chang, Chung-Ju
;
Ren, Fang-Ching
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電信工程研究所
In this paper, a fuzzy Q-learning-based hybrid automatic repeat request (FQL-HARQ) scheme is proposed to enhance the system performance of high speed downlink packet access (HSDPA) in universal mobile telecommunications system (UMTS). In the HSDPA system, it is an important issue to choose modulation and coding scheme (MCS) for new data packet when channel quality indicator (CQI) is inaccurate. Hence, the purpose of the FQL-HARQ scheme is to determine a suitable MCS for new data packet so as to maximize the system throughput while guarantee the block error rate (BLER) requirement. In the FQL-HARQ scheme, the fuzzy logic is used to choose a suitable MCS for each new data packet. According to the feedback information from the HSDPA system, the Q-learning algorithm is adopted to update fuzzy rule base. This makes the FQL-HARQ scheme can adapt to the variation of environment. Simulation results show that the proposed scheme can increase the system throughput of up to 70 % compared to the conventional adaptive method in the case with CQI report delay.
HARQ Control Scheme by Fuzzy Q-Learning for HSPA(+)
(2011)
Chung, Wen-Ching
;
Chen, Ying-Yu
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Chang, Chung-Ju
;
電機工程學系
;
Department of Electrical and Computer Engineering
In this paper, we propose a hybrid automatic repeat request (HARQ) control scheme by using fuzzy Q-learning algorithm for high speed packet access evolution (HSPA(+)) systems. The challenge of the HARQ control in HSPA(+) systems is the selection of MIMO (multiple-input multiple-output) configuration mode and MCS (modulation and coding scheme) level for new data transmission of HARQ, under the situation that the channel quality indication has report delay. The fuzzy Q-learning-based HARQ (FQL-HARQ) scheme can determine an appropriate MIMO configuration mode and MCS level for new data transmission so as to maximize the system throughput under the guaranteed block error rate (BLER) requirement. Simulation results show that, the proposed FQL-HARQ scheme increases the system throughput by up to 70.09% as compared to the conventional adaptive threshold method [4].
LINEAR STATE FEEDBACK DESIGN FOR SURGE CONTROL OF AXIAL FLOW COMPRESSOR DYNAMICS
(2014-06-01)
Liaw, Der-Cherng
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Huang, Yun-Hua
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Chung, Wen-Ching
;
交大名義發表
;
電控工程研究所
Based on Moore and Greitzer\'s model [15], the surge behavior of axial flow compression system was found to be attributed to the appearance of Andronov-Hopf bifurcationin [12]. In this paper, we focus on the design of control law to prevent and/or delay the occurrence of the bifurcations, which will then suppress the surge behavior. Both types of linear dynamic state feedback and linear washout filter controllers are proposed. The proposed washout design does not require the explicit knowledge of the operating point and keep the original equilibrium characteristic while the dynamic feedback design will change the equilibrium operating points for pre-surge and post-surge regime. In addition, the washout type control scheme can relax the implementation of the control law in the practical applications. Numerical results demonstrate the effectiveness of the proposed designs and the superiority of the washout filter scheme.
NACK-based Retransmission Schemes for MBMS over Single Frequency Network in LTE
(2011)
Lu, Cheng-Chung
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Chung, Wen-Ching
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Chang, Chung-Ju
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Ren, Fang-Ching
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電機工程學系
In this paper, we propose NACK-based retransmission schemes for multimedia broadcast and multicast service over single frequency network (MBSFN) in LTE systems to enhance goodput and reduce retransmission rate. It is known that more retransmissions in MBSFN will reduce the spectrum efficiency. Hence, to provide a reliable broadcast/multicast service in LTE systems is an important issue. We first group mobile users into three sets according to their SNRs. Each set can report NACK messages on dedicated or shared feedback channel. The retransmission is triggered by pre-defined probability or pre-defined threshold. By applying different retransmission trigger schemes on different feedback channels, we have four kinds of NACK-based retransmission schemes. Simulation results show that, the proposed retransmission schemes can enhance the goodput by up to 28.3% and reduce the retransmission rate by up to 37.8% compared to the conditional HARQ scheme [12].
The Steering Control of Vehicle Dynamics via a Lyapunov Redesign Approach
(2009)
Chung, Wen-Ching
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Liaw, Der-Cherng
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Chang, Shih-Tse
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電控工程研究所
;
Institute of Electrical and Control Engineering
In this paper, Lyapunov redesign method is proposed to control the steering of vehicle. It was observed in Liaw and Chung (2006) that the vehicle dynamics would exhibit the saddle-node bifurcation phenomenon at some front wheel steering angle. This might result in spin and/or instability for vehicle system. Based on the assumption of constant driving velocity, a Lyapunov redesign control law was proposed to stabilize the system dynamics at the bifurcation point for guaranteeing system stability after the appearance of stall. Simulation results for an example model of vehicle dynamics were presented to illustrate the success of the proposed design.