Browsing by Author "Chang, CJ"

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A cellular neural network and utility-based scheduler for multimedia CDMA cellular networks
(2005)
Shen, S
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Chang, CJ
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電信工程研究所
;
Institute of Communications Engineering
In this paper a cellular neural network and utility (CNNU)-based scheduler is proposed for multimedia CDMA cellular networks supporting differentiated quality-of-service (QoS). The cellular neural network is powerful for complicated optimization problems and implementable by circuits with rapid convergence to a desired equilibrium; the utility-based scheduling algorithm can efficiently utilize the radio resource for system and provide QoS requirements and fairness for connections. A relevant utility function for each connection is here defined as its radio resource function further weighted by both a QoS requirement deviation function and a fairness compensation function. The CNNU-based scheduler determines a radio resource assignment vector for all connections so that the overall system utility is maximized and the system throughput can be achieved as high as possible. At the same time, the performance measures of all connections are kept closed to their QoS requirements in an efficient way.
A channel borrowing scheme in a cellular radio system with guard channels and finite queues
(1996)
Chang, CJ
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Huang, PC
;
Su, TT
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電信工程研究所
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Institute of Communications Engineering
A channel effect prediction-based power control scheme using PRNN/ERLS for uplinks in DS-CDMA cellular mobile systems
(2006-01-01)
Chen, YS
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Chang, CJ
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Hsieh, YL
;
交大名義發表
;
National Chiao Tung University
This paper proposes a channel effect prediction-based power control scheme using pipeline recurrent neural network (PRNN)/extended recursive least squares (ERLS) for uplinks in direct sequence code division multiple access (DS-CDMA) cellular mobile systems. Conventional signal-to-interference (SIR) prediction-based power control schemes may incur prediction mistakes caused by the adjustment of transmission power. The proposed power control scheme purely tracks the variation of channel effect and, thus, can be immune to any power adjustment. Furthermore, it adopts the PRNN with ERLS for predicting the channel effect. Simulation results show that the channel effect prediction-based power control scheme using PRNN/ERLS achieves a 40% higher system capacity and a lower outage probability than the conventional SIR prediction-based power control scheme using grey prediction method (IEEE Trans. Veh. Technol., Vol. 49, No. 6, p. 2081, 2000).
A combined channel assignment mechanism for hierarchical cellular systems
(1998-09-01)
Lo, KR
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Chang, CJ
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Chang, C
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Shung, CB
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電子工程學系及電子研究所
This paper proposes a combined channel assignment (CCA) mechanism for hierarchical cellular systems with overlaying macrocells and overlaid microcells. The proposed CCA mechanism combines overflow, underflow, and reversible schemes, where new or handoff calls having no available channel to use in the overlaid microcell can overflow to use free channels in the overlaying macrocell, handoff calls from a neighboring macrocell can underflow to use free channels in the overlaid microcell, and handoff attempts from a macrocell-only region to an overlaid microcell can be reversed to use free channels in the microcell. We apply the CCA mechanism in two different hierarchical cellular systems of Strip type and Manhattan type and compare the CCA with the overflow channel assignment (OCA) scheme. Simulation results show that the CCA mechanism outperforms the OCA scheme by once in forced termination probability, by several times in new call blocking probability, and by 4.7% in system utilization for a hierarchical cellular system, and the CCA mechanism is more suitable for the Manhattan type than for the Strip type. (C) 1998 Elsevier Science B.V.
A fast multicast IP-rOuting lookup scheme
(2003-03-01)
Huang, KM
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Chang, CJ
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電信工程研究所
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Institute of Communications Engineering
This letter proposes a fast multicast IP-routing lookup scheme, which adopts a compression bit map conception for forwarding information. The proposed scheme-can achieve fast address lookup speed and reasonable forwarding table size.
A hierarchical cellular system with reneging and dropping for waiting new and handoff calls
(1997)
Chang, C
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Chang, CJ
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Lo, KR
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交大名義發表
;
電信工程研究所
In this paper, we analyze a hierarchical cellular system with overflow scheme and finite queues for new and handoff calls. The effect of guard channel scheme and the effects due to reneging of waiting new calls because of the caller's impatience and dropping of queued handoff call as the callers move out of the handoff area are considered. We successfully solve the system by adopting the multi-dimensional Markovian chain and use the transition-probability matrix and the signal-how graph to obtain the average new-call blocking probability, the forced termination probability, and the average waiting time of queued new and handoff calls. We further investigate how the guard channel scheme and buffer provision scheme affect the hierarchical cellular system. The results show that it seems unnecessary to provide guard channel and waiting buffer for microcells in the hierarchical cellular system with over flow mechanism.
A light-induced tunneling state in a submicron double barrier tunneling diode with a center-doped well
(2000-02-01)
Suen, YW
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Young, CC
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Chang, CJ
;
Wu, JC
;
Wang, SY
We will present the observation of a light-induced meta-stable impurity state in a submicron center-doped double barrier tunneling diode (DBRTD) manufactured by a novel single-step e-beam lithography process in which no further alignment for the interconnect between the bonding pad and the small active device region is required. We attribute the mete-stable tunneling state, which can be switched by light and high voltage bias, to the light- or field-induced charge redistribution in the active tunneling region. (C) 2000 Elsevier Science B.V. All rights reserved.
A neural fuzzy resource manager for hierarchical cellular systems supporting multimedia services
(2003-09-01)
Lo, KR
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Chang, CJ
;
Shung, CB
;
交大名義發表
;
National Chiao Tung University
Using intelligent techniques to perform radio resource management is an effective method. This paper proposes neural fuzzy control for radio resource management in hierarchical cellular systems supporting multimedia services. A neural fuzzy resource manager (NFRM) is designed, which mainly contains a neural fuzzy channel allocation processor (NFCAP), and NFCAP is in a two-layer architecture: a fuzzy cell selector (FCS) in the first layer and a neural fuzzy call-admission and rate controller (NFCRC) in the second layer. The FCS chooses not only the handoff failure. probabilities and the resource availabilities in both microcell and macrocell but also the mobility of user as input linguistic variables. The NFCRC takes the handoff failure probability and the resource availability of the selected cell as input variables to perform call admission control and rate control for the call. Simulation results show that NFRM can always gruarantee the quality of service (QoS) requirement of handoff failure probability for all traffic loads. Also, NFRM improves the system. utilization by 31.1% while increasing the handoff rate by 2% over the overflow channel allocation (OCA) scheme [3]; it enhances the system utilization by 6.3% and 1.4%, and still reduces the handoff rate by 14.9% and 6.8%, as compared to the combined channel allocation (CCA) scheme [201, [21] and fuzzy channel allocation control (FCAC) scheme [9], respectively, under a predefined QoS constraint.
A neural-net based fuzzy connection admission controller for wireless ATM
(1997)
Chen, YS
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Chang, CJ
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Tzou, WY
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Ren, FC
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交大名義發表
A neural-net based fuzzy connection admission controller for a wireless ATM network is designed in this paper. it is a QoS-guaranteed controller, where QoSs of both air interface and ATM network are taken into consideration. Hence, for the neural fuzzy admission decision controller, we further design fuzzy capacity requirement estimator, fuzzy air interface performance estimator, and fuzzy system status estimator for reflecting the equivalent capacity required by the new call request, air interface performance, and the ATM network status, respectively. The simulation result shows that the neural fuzzy connection admission controller can gain high bandwidth utilization for wireless ATM networks.
A novel dynamic cell configuration scheme in next-generation situation-aware CDMA networks
(2006-01-01)
Liao, CY
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Yu, F
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Leung, VCM
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Chang, CJ
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電信工程研究所
To balance the time-varying traffic load between cells, caused by user mobility and diverse applications, it is crucial for next-generation code-division multiple-access (CDMA) cellular networks to configure cell coverage and capacity dynamically. In this paper, we show that pilot power allocation is highly coupled to other facets of radio resource management. We propose a novel dynamic cell configuration scheme for multimedia CDMA cellular networks, based on reinforcement-learning, which takes into account pilot, soft handoff, and maximum link power allocations, as well as call admission control mechanisms. Simulation results demonstrate the effectiveness of the proposed scheme in situation-aware CDMA networks.
A novel dynamic cell configuration scheme in next-generation situation-aware CDMA networks
(2005)
Liao, CY
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Yu, F
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Leung, VCM
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Chang, CJ
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電信工程研究所
In next-generation CDMA networks, due to random user mobility and time-varying multimedia traffic activity, the system design of coverage and capacity is a challenging issue. To utilize radio resources efficiently, it is crucial for future cellular networks to be aware of the system situation and configures cell coverage and capacity dynamically to balance traffic loads over all cells. In this paper, we propose a novel dynamic cell configuration scheme in multimedia CDMA networks via reinforcement-learning, which takes into account pilot, soft handoff, and maximum link power allocations as well as call admission control mechanisms. Simulation results demonstrate the effectiveness of the proposed scheme in situation-aware CDMA networks.
A power control scheme with link gain prediction using PRNN/ERLS for DS-CDMA cellular mobile systems
(2003)
Hsieh, YL
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Chang, CJ
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Chen, YS
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電信工程研究所
;
Institute of Communications Engineering
In this paper, a link gain prediction-based power control scheme is designed for DS-CDMA cellular mobile systems. The link gain prediction can help to remove the interference of the power control adjustment itself. The pipeline recurrent neural network (PRNN) with extended recursive least square (ERLS) is adopted for the prediction. This PRNN/ERLS predictor possesses infinite memory of past signals so that it can capture precisely the signal correlation and improve the delay compensation of power control. Simulation results show that the link gain prediction-based power control scheme using PRNN/ERLS has lower outage probability than the received SIR prediction-based power control scheme using grey prediction method [5] and improves the system capacity by an amount of 41.6%.
A power-spectrum based neural fuzzy connection admission mechanism for ATM networks
(1997)
Chang, CJ
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Lin, SY
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Shiue, YR
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Cheng, RG
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交大名義發表
ATM (asynchronous transfer mode) networks support services with bursty traffic. A sophisticated and real-time admission controller is needed not only to guarantee the required quality-of-service (QoS) for existing calls but also to achieve higher system efficiency. In this paper, we propose a power-spectrum based neural fuzzy connection admission control (PNFCAC) mechanism for an ATM network. Power-spectrum of input process explicitly describes the correlation behavior of input traffic and has a great impact on the queueing behavior of an ATM net work. The neural fuzzy controller has been successfully applied to deal with the complex problem which can not be analyzed by classical methods based on probability theory and bivalent logic for recent years. Under the constraint of QoS, we construct a decision hyperplane of the connection admission control according to parameters of the power spectrum. We further adopt the learning/adapting capabilities of the neural network to adjust the optimum location of the boundary between these two decision space. Simulation results show that the PNFCAC mechanism provides a superior system utilization over the conventional CAC schemes and the neural fuzzy CAC using time-domain analysis, while keeping the QoS contract.
A priority TCAM IP-Routing lookup scheme
(2003-07-01)
Lin, PC
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Chang, CJ
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電信工程研究所
;
Institute of Communications Engineering
A priority TCAM IP-routing lookup scheme, which combines a priority ternary content addressable memory (TCAM) technique with a compact IP-routing lookup scheme, is proposed in this letter. It not only completes an IP-routing lookup with two memory accesses but also achieves small lookup table size and fast table reconstruction time.
A Q-learning-based multi-rate transmission control scheme for RRC in WCDMA systems
(2002-01-01)
Ren, FC
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Chang, CJ
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Chen, YS
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交大工研院聯合研發中心
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NCTU/ITRI Joint Research Center
In this paper, a Q-learning-based multi-rate transmission control scheme (Q-MRTC) for radio resource control (RRC) in WCDMA systems is proposed. The RRC problem is modelled as a semi-Markov decision process (SMDP). And we successfully apply a real-time reinforcement learning algorithm, named Q-learning, to accurately estimate the transmission cost for the multi-rate transmission control. For the cost function approximation, we apply the feature extraction method to map the original state space into a more compact set which represents the resultant interference profile. Simulation results show that the Q MRTC can achieve higher system throughput and better users' satisfaction index, by an amount of 87% and 50%, respectively, than the interference-based multi-rate transmission control scheme, while keeping the QoS requirement.
A QoS-guaranteed fuzzy channel allocation controller for hierarchical cellular systems
(2000-09-01)
Lo, KR
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Chang, CJ
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Chang, C
;
Shung, CB
;
電信工程研究所
This paper proposes a fuzzy channel allocation controller (FCAC) for hierarchical cellular systems. The FCAC mainly contains a fuzzy channel allocation processor (FCAP) which is designed to be in a two-layer architecture that consists of a fuzzy admission threshold estimator in the first layer and a fuzzy channel allocator in the second layer. The FCAP chooses the handoff failure probability, defined as quality-of-service (QoS) index, and the resource availability as input linguistic variables for the fuzzy admission threshold estimator, where the Sugeno's position gradient-type reasoning method is applied to adaptively adjust the admission threshold for the fuzzy channel allocator. And the FCAP takes the mobility of user, the channel utilization, and the resource availability as input variables for the fuzzy channel allocator so that the channel allocation is finally determined, further based upon the admission threshold. Simulation results show that FCAC can always guarantee the QoS requirement of handoff failure probability for all traffic loads, Also it improves the system utilization by 31.2% while it increases the handoff rate by 12.9% over the overflow channel allocation (OCA) scheme [7]; it enhances the system utilization by 6% and still reduces the handoff rate by 6.7% as compared to the combined channel allocation (CCA) scheme [10], under a defined QoS constraint.
A QoS-provisioning neural fuzzy connection admission controller for multimedia high-speed networks
(1999-02-01)
Cheng, RG
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Chang, CJ
;
Lin, LF
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電信工程研究所
;
電信研究中心
This paper proposes a neural fuzzy approach for connection admission control (CAC) with QoS guarantee in multimedia high-speed networks. Fuzzy logic systems have been successfully applied to deal with traffic-control-related problems and have provided a robust mathematical framework for dealing with real-world imprecision. However, there is no clear and general technique to map domain knowledge on traffic control onto the parameters of a fuzzy logic system. Neural networks have learning and adaptive capabilities that can be used to construct intelligent computational algorithms for traffic control. However, the knowledge embodied in conventional methods is difficult to incorporate into the design of neural networks. The proposed neural fuzzy connection admission control (NFCAC) scheme is an integrated method that combines the linguistic control capabilities of a fuzzy logic controller and the learning abilities of a neural network. It is an intelligent implementation so that it can provide a robust framework to mimic experts' knowledge embodied in existing traffic control techniques and can construct efficient computational algorithms for traffic control. We properly choose input variables and design the rule structure for the NFCAC controller so that it can have robust operation even under dynamic environments. Simulation results show that compared with a conventional effective-bandwidth-based CAC, a fuzzy-logic-based CAC, and a neural-net-based CAC, the proposed NFCAC can achieve superior system utilization, high learning speed, and simple design procedure, while keeping the QoS contract.
A utility-based scheduling algorithm with differentiated QoS provisioning for multimedia CDMA cellular networks
(2004)
Shen, S
;
Chang, CJ
;
電信工程研究所
;
Institute of Communications Engineering
In this paper, we propose a utility-based scheduling algorithms with three generalized design aspects of link adaptation, QoS requirement achievement, and weighted fairness for multimedia CDMA network. Both dedicated and shared channels serve different classes of services. Per class QoS requirements are defined by both packet level, such as BER, and call level, such as, delay bound, packet dropping ratio, and minimum transmission rate. The utility function of each connection is the radio resource function weighted by both the QoS requirement achievement function and weighted fairness function. The system resource is scheduled via maximizing the overall system utility while the weighted fairness and the QoS requirements are kept. The optimal scheduling solution is derived as a resource assignment vector for active connections by solving the optimization of overall utility function via a polymatroid structure.
A variable partition duplex scheme on packet reservation multiple access protocol (VPD-PRMA)
(1998)
Chang, C
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Chang, CJ
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電信工程研究所
;
Institute of Communications Engineering
A variable partition duplex scheme on packet reservation multiple access protocol (VPD-PRMA) is proposed in this paper. Variable partition duplex scheme allows both uplink and downlink traffic to share a common communication resource and takes advantage of the nature of a conversation pair that only one party is talking in most of the conversation intervals. By adopting VPD-PRMA, wireless communication systems can get higher statistical multiplexing gain due to the trunking effect. We study performance of the VPD-PRMA system by computer simulation. The results show that the system capacity of VPD-PRMA system is 23 and that of traditional PRMA system is 19. By adopting VPD-PRMA on DECT frame structure, the total capacity of VPD-PRMA system is 230 voice channels, which is almost twice the capacity (120 channels) of the typical DECT system.
A variable partition duplex scheme with enlarged reservation duration on packet reservation multiple access protocol
(1999-05-01)
Chang, C
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Chang, CJ
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電信工程研究所
;
Institute of Communications Engineering
A variable partition duplex scheme on packet reservation multiple access protocol (VPD-PRMA) is analyzed in this paper. We assume a four-state speech model for a conversational pair and successfully obtain performance measures by approximate Markovian analysis. Analytical results show that they quite fit simulation results; and VPD-PRMA can get higher statistical multiplexing gain than fixed partition duplex (FPD)-PRMA, due to the trunking effect. We further investigate the effect of design parameters of permission probability and enlarged reservation duration on system performance by computer simulation. Simulation results shows that it exists appropriate values for these two design parameters so that the packet dropping probability can be minimized. The adjustment of permission probability can greatly improve the performance of uplink traffic with slight deterioration of the performance of downlink traffic; the provision of enlarged reservation duration scheme can enhance the system performance.