Browsing by Author "Chang, Chung-Ju"

Now showing 1 - 20 of 84

A Balanced Resource Scheduling Scheme With Adaptive Priority Thresholds for OFDMA Downlink Systems
(2012-03-01)
Chung, Yao-Hsing
;
Chang, Chung-Ju
;
交大名義發表
;
電機工程學系
;
National Chiao Tung University
This paper proposes a new balanced resource scheduling (BRS) scheme with adaptive priority thresholds for orthogonal frequency-division multiple-access (OFDMA) downlink systems. The BRS scheme achieves an excellent balance between quality-of-service (QoS) requirement guarantee and system throughput enhancement, whereas conventional schemes cannot explicitly and accurately control this tradeoff. Based on the adaptive priority threshold of each user, the BRS scheme first performs a priority-based resource allocation (RA) algorithm for users whose priority value is larger than its priority threshold to fulfill the QoS requirement. The BRS scheme then performs a channel-state-information (CSI)-based RA algorithm for the remaining users to enhance system throughput. To achieve balance between QoS guarantee and throughput enhancement, a fuzzy inference priority threshold generator adaptively and intelligently adjusts the priority threshold of each user. Simulation results show that the proposed BRS scheme with adaptive priority threshold enhances the system throughput by 16%, 8.5%, 8.2%, and 46.8% at traffic load of 0.93, compared with conventional adaptive radio RA (RRA), utility-based RRA, utility-based throughput maximization and complexity reduction scheduling, and fairness and QoS guarantee scheduling with fuzzy controls schemes, respectively, under a QoS requirement guarantee. This approach also outperforms the BRS scheme with fixed priority thresholds in both throughput enhancement and QoS guarantee.
A Bargaining Game Based Access Network Selection Scheme for HetNet
(2014-01-01)
Liou, Yi-Shing
;
Gau, Rung-Hung
;
Chang, Chung-Ju
;
電機資訊學士班
;
Undergraduate Honors Program of Electrical Engineering and Computer Science
We propose a novel bargaining-game-based access network selection scheme for call requests in heterogeneous networks (HetNet). The bargaining game takes into consideration a number of factors including the mobility pattern of the mobile device, the load of the candidate access network, and the preference of the candidate access network to the call request. The studied bargaining game has a unique solution since the set of feasible payoff vectors is convex. Simulation results show that the proposed scheme could significantly outperform the TOPSIS scheme and the evolutionary game approach in terms of the handoff occurrence ratio and the call dropping probability.
A Cellular Neural Network and Utility-Based Radio Resource Scheduler for Multimedia CDMA Communication Systems
(2009-11-01)
Shen, Scott
;
Chang, Chung-Ju
;
Wang, Li-Chun
;
電機工程學系
;
Department of Electrical and Computer Engineering
The paper proposes a cellular neural network and utility (CNNU)-based radio resource scheduler for multimedia CDMA communication systems supporting differentiated quality-of-service (QoS). Here, we define a relevant utility function for each connection, which is its radio resource function weighted by a QoS requirement deviation function and a fairness compensation function. We also propose cellular neural networks (CNN) to design the utility-based radio resource scheduler according to the Lyapunov method to solve the constrained optimization problem. The CNN is powerful for complicated optimization problems and has been proved that it can rapidly converge to a desired equilibrium; the utility-based scheduling algorithm can efficiently utilize the radio resource for system, keep the QoS requirements of connections guaranteed, and provide the weighted fairness for connections. Therefore, the CNNU-based scheduler, which determines a radio resource assignment vector for all connections by maximizing an overall system utility, can achieve high system throughput and keep the performance measures of all connections to meet their QoS requirements. Simulation results show that the CNNU-based scheduler attains the average system throughput greater than the EXP [9] and the HOLPRO [5] scheduling schemes by an amount of 23% and 33%, respectively, in the QoS guaranteed region.
A Cognitive Priority-based Resource Management Scheme for Cognitive Femtocells in LTE Systems
(2013-01-01)
Chung, Wen-Ching
;
Chang, Chung-Ju
;
Ye, Chang-Cing
;
電機資訊學士班
;
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 Coordination Based Resource Management Scheme with QoS Provisioning for Multicell OFDMA Downlink Systems
(2014-01-01)
Chung, Yao-Hsing
;
Chang, Chung-Ju
;
電機資訊學士班
;
Undergraduate Honors Program of Electrical Engineering and Computer Science
In this paper, we propose a coordination based resource management (CBRM) scheme with quality-of-service (QoS) provisioning for multicell OFDMA downlink systems. The proposed CBRM scheme cooperates with the multiple point deployment and the enhanced fractional frequency reuse (FFR). To solve the intra-cell interference brought by multiple point deployment, the CBRM scheme adopts a utility function to coordinate TPs and then maximizes system throughput and fulfills QoS requirements. Simulation results show that the CBRM scheme enhances the system throughput by amounts of 113% and 89% compared to the conventional FFR scheme [1] and the dynamic interference avoidance (DIA) scheme [6], respectively. Moreover, the CBRM scheme provides good QoS guarantee for both real-time and non-real-time
A Cost-Effective Strategy for Road-Side Unit Placement in Vehicular Networks
(2012-08-01)
Wu, Tsung-Jung
;
Liao, Wanjiun
;
Chang, Chung-Ju
;
電機工程學系
;
Department of Electrical and Computer Engineering
In this paper, we study the Roadside Unit (RSU) placement problem in vehicular networks. We focus on the highway-like scenario in which there may be multiple lanes with exits or intersections along the road. In our model, each vehicle can access RSUs in two ways: 1) direct delivery, which occurs when the vehicle is in the transmission range of the RSUs, and 2) multi-hop relaying, which takes place when the vehicle is out of RSU transmission range. We account for both access patterns in our placement strategy and formulate this placement problem via an integer linear programming model such that the aggregate throughput in the network can be maximized. We also take into account the impact of wireless interference, vehicle population distribution, and vehicle speeds in the formulation. The performance of the proposed placement strategy is evaluated via ns-2 simulations together with VanetMobisim to generate vehicle mobility patterns. The results show that our strategy leads to the best performance as compared with the uniformly distributed placement and the hot spot placement. More importantly, our solution needs the least number of RSUs to achieve the maximal aggregate throughput in the network, indicating that our scheme is indeed a cost effective yet highly efficient placement strategy for vehicular networks.
A Cross-Layer Congestion Avoidance Routing Scheme in Vehicular Ad Hoc Networks
(2014-01-01)
Yang, Chiao-Ling
;
Chung, Yao-Hsing
;
Chen, Chen-Yu
;
Chang, Chung-Ju
;
電機資訊學士班
We propose a cross-layer congestion avoid-ance routing (CCAR) scheme for VANETs based on IEEE 802.11p/WAVE (wireless access in vehicular environment) protocol. Due to highly dynamic network topology, the forwarders are selected one by one. The CCAR scheme first adjust the number of candidates adaptively so that senders have high probability to find a candidate as the forwarder. Then it dynamically adjusts the selection probability of each service channel (SCH) based on traffic load of SCHs to make channel load balanced. Finally, the CCAR scheme takes the number of co-channel senders, the loads of each possible forwarder, and the vehicular moving direction into account to determine the most appropriate route for senders. Simulation results show that the proposed CCAR scheme achieves lower packet delay (higher system uplink through-put) than the conventional GyTAR and AODV schemes by amounts of 95% and 95.7%, (8.4% and 19.2%,) respectively, when the number of vehicles is 150.
A fast handoff protocol for cellular IEEE 802.11e WLAN systems
(2007-02-01)
Chen, Yung-Han
;
Chang, Chung-Ju
;
電信工程研究所
;
Institute of Communications Engineering
This letter proposes a fast handoff protocol (FHP) for cellular IEEE 802.11e wireless local area network (WLAN) systems. The FHP, which is standard compatible, provides a controlled contention period (CCP) designated for handoff requests (HO-REQs), arranges these HO-REQs to contend sequentially in CCP, and proposes a fuzzy adjustment method (FAM) to determine a proper length for CCR Simulation results reveal that the FHP can significantly decrease the forced termination rate of HO-REQs and still enhance the system throughput of contention period for cellular IEEE 802.11e WLAN systems.
A Fuzzy Cache Lifetime Determination Scheme for LISP Mapping Systems
(2013)
Chen, Sheng-Chang
;
Chang, Chung-Ju
;
Chu, Yu-Huang
;
電機工程學系
;
Department of Electrical and Computer Engineering
Locator/ID Separation Protocol (LISP) is a simple and network-based architecture that can be used to address the scalability problem in the future Internet. The key function of LISP is the mapping system, which is responsible to map ID to locator. Usually, the cache table is used to store the queried mapping information. However, if the mapping information is changed, how to efficiently update and refresh the mapping information in the cache table is a very important issue. In this paper, we propose a fuzzy cache lifetime determination (FCLD) scheme for the LISP mapping system. This FCLD scheme adopts the fuzzy logic theory to generate and adjust cache lifetime of mapping information. It considers the update and lookup frequency, and lookup latency of mapping information as input linguistic variables to adjust the cache lifetime. In the high update and lookup frequency, the cache lifetime will be decreased to increase the accuracy of mapping information. In high lookup latency, the cache lifetime will be increased to reduce the overhead of inquiring mapping information. Simulation results show that the FCLD scheme has lower average packet delay by 10.78% and lower packet loss ratio by 2.1% than the solicit map request (SMR) scheme.
A Fuzzy Inter-Ring Route Control with PRNN Predictor Bridged Resilient Packet Rings
(2010)
Tang, Wen-Shiang
;
Chang, Chung-Ju
;
電機工程學系
;
Department of Electrical and Computer Engineering
In this paper, we propose an intelligent inter-ring route control, called fuzzy inter-ring route control with PRNN predictor (FIRC-P), for the bridged resilient packet rings (BRPR). The FIRC-P contains three functional blocks implemented by fuzzy logic systems or pipeline recurrent neural networks (PRNN): fuzzy bridge-node congestion indicator (FBCI), PRNN downstream-node fairness predictor (PDFP), and fuzzy route controller (FRC). The determination of the FIRC-P is based on the load balancing principle, in which the CW or CCW ringlet with lower congestion degree and higher service rate will be chosen. Simulation results show that the FIRC-P improves the performance by about 10% and 220% in packet dropping probability, by about 13% and 18% in average packet delay, and by about 6% and 19% in throughput over the queue length threshold route controller (QTRC) and the shortest path route controller (SPRC), respectively.
A Green Radio Resource Allocation Scheme for LTE-A CoMP Systems with Multimedia Traffic
(2013)
Chung, Wen-Ching
;
Chang, Chung-Ju
;
Huang, Chin-Ya
;
Teng, Hsin-Ying
;
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 joint power and rate assignment algorithm for multirate soft handoffs in mixed-size WCDMA cellular systems
(2007-05-01)
Liao, Ching-Yu
;
Chang, Chung-Ju
;
Wang, Li-Chun
;
Chen, Yih-Shen
;
交大名義發表
This paper proposes a joint power and rate assignment (JPRA) algorithm to deal with multirate soft handoffs (SHOs) in mixed-size wideband code division multiple access cellular systems. This JPRA algorithm contains a link proportional power allocation scheme and an evolutionary computing rate assignment method to determine an appropriate allocation of transmission power and service rate for multirate SHOs. It can achieve power balancing among cells better than the conventional site-selection diversity transmission scheme with best effort rate allocation. Simulation results show that the JPRA algorithm can achieve better cell's service coverage! and higher system capacity with and without the measurement errors during the active set selection.
A low-complexity beamforming-based scheduling to downlink OFDMA/SDMA systems with multimedia traffic
(2011-04-01)
Chung, Wen-Ching
;
Wang, Li-Chun
;
Chang, Chung-Ju
;
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
;
Chang, Chung-Ju
;
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 Nonlinear-Predictive QoS-Promoted Dynamic Bandwidth Allocation Scheme for Triple-play Services in Ethernet Passive Optical Networks
(2009)
Peng, Jan-Wen
;
Chang, Chung-Ju
;
Tien, Po-Ling
;
電機工程學系
;
Department of Electrical and Computer Engineering
This paper proposes a nonlinear-predictive QoS-promoted dynamic bandwidth allocation (NQ-DBA) scheme for upstream transmission in Ethernet passive optical network (EPON) systems. The proposed NQ-DBA scheme divides incoming packets of voice, video, data service into six priorities, whereas packets having less room before QoS requirements violation will be dynamically promoted to high priority. It predicts packets arriving at a prediction interval for ONUs using a nonlinear pipelined structure of recurrent neural network (RNN) with extended recursive least squares (ERLS) update so that the bandwidth allocation can be more up-to-date and then accurate. Simulation results show that the proposed NQ-DBA scheme achieves higher system utilization than the DBAM scheme by 4%, and 21%, 90%, 43%, respectively.
A Novel Adaptive P-Persistent MAC Scheme for WLAN Providing Low Delay Variance
(2006)
Chang, Chung-Ju
;
Yen, Frank C. M.
;
Chen, Yih-Shen
;
Huang, ChingYao
;
電信工程研究所
The paper proposes and analyzes a novel adaptive p-persistent-based (APP) medium access control (MAC) scheme to provide low delay variance for IEEE 802.11 WLAN. The APP MAC scheme can differentiate permission probabilities of transmission for stations being incurred with different packet delays, and the permission probability is designed as a function of the numbers of retransmissions and re-backoffs so that stations being with larger packet delay can attain higher permission probability. Additionally, the scheme is modeled by a Markov-chain and successfully analyzed, where the system throughput and delay are derived. Results show that the proposed APP MAC scheme can achieve lower delay variance than conventional algorithms; it can effectively reduce the collision probability and the mean delay, therefore, the mean throughput is enhanced, as well.
A Predictive Intelligent Traffic Controller for Broadband Multimedia IP Networks
(2008)
Lin, Li-Fong
;
Chang, Chung-Ju
;
Cheng, Ray-Guang
;
電信工程研究所
;
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.
A Preference Value-Based Cell Selection Scheme in Heterogeneous Wireless Networks
(2010)
Chang, Chung-Ju
;
Hsieh, Chih-Yuan
;
Chen, Yung-Han
;
電信工程研究所
;
Institute of Communications Engineering
This paper proposes a preference value-based cell selection (PVCS) scheme to satisfy quality of service (QoS) requirements, maximize accommodated number of calls, and minimize handoff occurrence frequency in heterogeneous wireless networks. The PVCS scheme contains three stages including candidate cells selection, preference value calculation, and target cell determination. The candidate cells selection is used to sift the suitable cells for the call request. All suitable cells form a candidate cell set. The preference value calculation computes the preference value of each cell in the candidate cell set, which is optimized by considering QoS factor, loading factor, and mobility factor, for the purpose of maintaining QoS requirements of a call request, maximize accommodated number of calls, and minimizing handoff occurrence frequency. Eventually, the candidate cell, which has the maximum preference value, would be selected for the call request. Simulation results show that PVCS scheme achieves higher total throughput than UGT while satisfying the QoS requirements. It also has lower new call blocking rate and handoff call dropping rate than UGT, which means more accommodated calls than UGT. Besides, PVCS reduces the total handoff occurrence frequency by about 20% as compared to UGT.