Browsing by Author "Tien, PL"

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A Contention Access Protocol with Dynamic Bandwidth Allocation for wireless ATM networks
(2000)
Yuang, MC
;
Tien, PL
;
Chen, CS
;
資訊工程學系
;
Department of Computer Science
In this paper, we propose a new Contention Access Protocol (CAP) augmented with a Dynamic Bandwidth Allocator (DBA) for wireless ATM networks supporting ABR and Signaling Control (SCR) traffic. CAP incorporates a dynamic tree-splitting collision resolution algorithm parameterized by an optimal Splitting Depth (SD). DBA performs estimation and on-line prediction of ABR self-similar traffic characteristics. It in turn determines the optimal SD per every frame, satisfying ABR throughput and SCR blocking probability requirements while retaining maximal aggregate throughput. Simulation results postulate the optimal SD's under various ABR and SCR traffic conditions. These results are then off-line trained and constructed by a Back Propagation Neural Network (BPNN), which is used on-line for optimal bandwidth allocation.
A Lagrangean relaxation-based approach for routing and wavelength assignment in multigranularity optical WDM networks
(2004-11-01)
Lee, SSW
;
Yuang, MC
;
Tien, PL
;
Lin, SH
;
資訊工程學系
Optical wavelength-division multiplexed (WDM) networks often include optical cross-connects with multigranularity switching capability such as switching on a single lambda, a waveband, or an entire fiber basis. In addition, it has been shown that routing and wavelength assignment (RWA) in an arbitrary mesh WDM network is an NP-complete problem. In this paper, we propose an efficient approximation approach, called Lagrangean relaxation with heuristics (LRH), aimed to resolve RWA in multigranularity WDM networks particularly with lambda and fiber switches. The task is first formulated as a combinatorial optimization problem in which the bottleneck link utilization is to be minimized. The LRH approach performs constraint relaxation and derives a lower-bound solution index according to a set of Lagrangean multipliers generated through subgradient-based iterations. In parallel, using the generated Lagrangean multipliers, the LRH approach employs a new heuristic algorithm to arrive at a near-optimal upper-bound solution. With lower and upper bounds, we conduct a performance study on LRH with respect to accuracy and convergence speed under different parameter settings. We further draw comparisons between LRH and an existing practical approach via experiments over randomly generated and several well-known large sized networks. Numerical results demonstrate that LRH outperforms the existing approach in both accuracy and computational time complexity, particularly for larger sized networks.
A novel intra-media synchronization mechanism for multimedia communications
(1996)
Yuang, MC
;
Tien, PL
;
資訊工程學系
;
Department of Computer Science
A QoS packet/burst scheduler for broadband networks
(2002)
Yuang, MC
;
Shih, J
;
Tien, PL
;
資訊工程學系
;
Department of Computer Science
Prevailing weight-based scheduling algorithms advocate static or coarse-grained simplification of timestamp computation, resulting in performance bottleneck and unnecessary downgrade under heavy and normal computation loads, respectively. Our goal is to design a scheduler that enables quantitative trade-off balance between performance and complexity. In this paper, we propose a Stepwise QoS Scheduler (SQS), enabling packet to burst scheduling under normal to heavy computation loads, based on a new notion of window. Window sizes of unity and greater than one correspond to packet and burst scheduling, respectively. SQS exerts simple FIFO service within the window and guarantees stepwise weight-proportional service at the window boundary. As a result, quantitative trade-off balance can be facilitated via the adjustment of the window size. We further formally specify the SQS service guarantee for a flow by a stepwise service curve, which is a function of W and theta(min) - the least-upper-bound delay incurred by the first packet of the busy period of the flow. Finally, we demonstrate through experimental results that, by applying a small window (W less than or equal to 10), SQS outperforms Weighted Fair Queueing (WFQ) and performs as superior as Worst-case Fair Weighted Fair Queueing (WF(2)Q) with respect to throughput fairness, mean delay, and worst-case delay fairness.
A synchronization paradigm with QoS guarantees for multimedia communications
(1999)
Yuang, MC
;
Lo, BC
;
Chen, YG
;
Tien, PL
;
資訊工程學系
In this paper, we propose a synchronization paradigm, called SYNC*, offering two Quality of Service (QoS) requirements, skew and throughput, for multimedia communications. SYNC* is composed of three components: Intelligent Video Smoother (IVS), Synchronizer, and Multi-thread Priority Manager (MPM). While IVS and Synchronizer achieves intramedia and Intermedia synchronization, respectively, MPM ensures satisfactory throughput before playout. The main goal of the paper is to present in detail the design and performance analysis of the second component, Synchronizer. Synchronizer is aimed to achieve bounded skew between different media through periodic marking of correlated frames. The minimum marking interval yielding a given skew is analytically determined based on a Markov Batch Bernoulli Process (MBBP)/D/K/1 queueing model. We demonstrate the profound agreement between analytic and simulation results. The results also indicate that, the playout quality with respect to skew is highly relevant to the traffic burstiness and decoder buffer size. On the basis of a fixed marking interval, the greater the burstiness and buffer size, the poorer the playout quality.
Intelligent video smoother for multimedia communications
(1996)
Yuang, MC
;
Tien, PL
;
交大名義發表
;
資訊工程學系
;
National Chiao Tung University
Multimedia communications often require intra-media synchronization for video data to prevent potential playout discontinuity resulting from network delay variation while still achieving satisfactory playout throughput. In this paper, we propose a neural-network-based intra-video synchronization mechanism, called Intelligent Video Smoother (NS), operating at the application layer of the receiving end system. IVS is composed of a Neural Network (NN) Traffic Predictor, an NN Window Determinator, and a window-based playout smoothing algorithm. The NN Traffic Predictor employs an on-line-trained Back Propagation Neural Network (BPNN) to periodically predict the characteristics of traffic modelled by a generic Interrupted Bernoulli Process (IBP) over a future fixed time period. With the predicted traffic characteristics, the NN Window Determinator determines the corresponding optimal window by means of an off-line-trained BPNN in an effort to achieve a maximum of the playout Quality (Q) value. The window-based playout smoothing algorithm then dynamically adopts various playout rates according to the window and the number of packets in the buffer. Finally, we show via simulation results that, compared to two other playout approaches, IVS achieves high-throughput and low-discontinuity playout under a mixture of IBP arrivals.
Intelligent video smoother for multimedia communications
(1997-02-01)
Yuang, MC
;
Tien, PL
;
Liang, ST
;
交大名義發表
;
資訊工程學系
Multimedia communications often require intramedia synchronization for video data to prevent potential playout discontinuity resulting from network delay variation (jitter) while still achieving satisfactory playout throughput. In this paper, we propose a neural network (NN) based intravideo synchronization mechanism, called the intelligent video smoother (IVS), operating at the application layer of the receiving end system. The IVS is composed of an NN traffic predictor, an NN window determinator, and a window-based play out smoothing algorithm, The NN traffic predictor employs an on-line-trained back-propagation neural network (BPNN) to periodically predict the characteristics of traffic modeled by a generic interrupted Bernoulli process (IBP) over a future fixed time period. With the predicted traffic characteristics, the NN window determinator determines the corresponding optimal window by means of an off-line-trained BPNN in an effort to achieve a maximum of the playout quality (Q) value. The window-based playout smoothing algorithm then dynamically adopts various playout rates according to the window and the number of packets in the buffer, Finally, we show that via simulation results and live video scenes, compared to two other playout approaches, IVS achieves high-throughput and low-discontinuity playout under a mixture of IBP arrivals.
Intelligent voice smoother for silence-suppressed voice over Internet
(1999-01-01)
Tien, PL
;
Yuang, MC
;
資訊工程學系
;
Department of Computer Science
When transporting voice data with silence suppression over the Internet, the problem of jitter introduced from the network often renders the speech unintelligible. It is thus indispensable to offer intramedia synchronization to remove jitter while retaining minimal playout delay (PD), In this paper, we propose a neural network (NN)-based intravoice synchronization mechanism, called the intelligent voice smoother (IVoS), IVoS is composed of three components: 1) the smoother buffer; 2) the NN traffic predictor; and 3) the constant bit rate (CBR) enforcer. Newly arriving frames, assumed to follow a generic Markov modulated Bernoulli process (MMBP), are queued in the smoother buffer. The NN traffic predictor employs an online-trained back propagation NN (BPNN) to predict three traffic characteristics of every newly encountered talkspurt period. Based on the predicted characteristics, the CBR enforcer derives an adaptive buffering delay (ABD) by means of a near-optimal simple closed-form formula. It then imposes the delay on the playout of the first frame in the talkspurt period. The CBR enforcer in turn regulates CBR-based departures for the remaining frames of the talkspurt, aiming at assuring minimal mean and variance of distortion of talkspurts (DOT) and mean PD. Simulation results reveal that, compared to three other playout approaches, IVoS achieves superior playout, yielding negligible DOT and PD, irrespective of traffic variation.
Intelligent voice smoother for silence-suppressed voice over Internet
(1998)
Tien, PL
;
Yuang, MC
;
資訊工程學系
;
Department of Computer Science
For transporting voice data with silence suppression over the Internet, the problem of jitter introduced from the network often renders the speech unintelligible. It is thus indispensable to offer intramedia synchronization to remove jitter while retaining minimal playout delay. In this paper, we propose a neural-network-based intra-voice synchronization mechanism, called the Intelligent Voice Smoother (IVoS). IVoS is composed of three components: Smoother Buffer, Neural Network (NN) Traffic Predictor, and Constant Bit Rate (CBR) Enforcer. Newly arriving frames, being assumed to follow a generic Markov Modulated Bernoulli Process (MMBP), are queued in the Smoother Buffer. The NN Traffic Predictor employs an on-line-trained Back Propagation Neural Network (BPNN) to predict three traffic characteristics of every newly encountered talkspurt period. Based on the predicted characteristics, the CBR Enforcer derives an adaptive buffering delay. It then imposes such delay on the playout of the first frame in the talkspurt period. The CBR Enforcer in turn regulates CBR-based departures for the remaining frames of the talkspurt, aiming at assuring minimal mean and variance of Distortion of Talkspurts (DOT) and mean playout Delay (PD). Simulation results reveal that, compared to three other playout approaches, IVoS achieves superior playout yielding negligible DOT and PD irrespective of traffic variation.
Intelligent Voice Smoother for VBR voice over ATM networks
(1998)
Tien, PL
;
Yuang, MC
;
資訊工程學系
;
Department of Computer Science
For distinctively transporting voice data with silence suppression over Asynchronous Transfer Mode (ATM) networks via the Variable Bit Rate (VBR) service, the problem of jitter introduced from the network often renders the speech unintelligible. It is thus indispensable to offer intramedia synchronization to remove jitter while retaining minimal playout delay. In this paper, we propose a neural-network-based intra-voice synchronization mechanism, called the Intelligent Voice Smoother (IVoS). IVoS is composed of three components: Smoother Buffer, Neural Network (NN) Traffic Predictor, and Constant Bit Rate (CBR) Enforcer. Newly arriving frames, being assumed to follow a generic Markov Modulated Bernoulli Process (MMBP), are queued in the Smoother Buffer. The NN Traffic Predictor employs an on-line-trained Back Propagation Neural Network (BPNN) to predict three traffic characteristics of every newly encountered talkspurt period. Based on the predicted characteristics, the CBR Enforcer derives an adaptive buffering delay by means of a near optimal, simple, closed-form formula. It then imposes such delay on the playout of the first frame in the talkspurt period. The CBR Enforcer in turn regulates CBR-based departures for the remaining frames of the talkspurt, aimed at assuring minimal mean and variance of Distortion of Talkspurts (DOT) and mean playout Delay (PD). Simulation results reveal that, compared to three other playout approaches, IVoS achieves superior playout yielding negligible DOT and PD irrespective of traffic variation.
Intra-media synchronization for multimedia communications
(1994)
Yuang, MC
;
Tien, PL
;
交大名義發表
;
資訊工程學系
;
National Chiao Tung University
Multimedia communications require intra-media synchronization for video data to prevent potential playout discontinuity resulting from network delay variation (jitter) while still achieving satisfactory playout throughput. In this paper, we propose a neural-network-based intra-media synchronization mechanism, called Neural Network Smoother (NNS). NNS is composed of a Neural Network (NN) Traffic Predictor, an NN Window Determinator, and a window-based playout smoothing algorithm. The NN Traffic Predictor employs an on-line-trained Back Propagation Neural Network (BPNN) to periodically predict future traffic characteristics. The NN Window Determinator determines the corresponding optimal window by means of an off-line-trained BPNN in an effort to achieve a maximum of the playout Quality (Q) value. According to the window, the window-based playout smoothing algorithm then dynamically adopts various playout rates. Compared to two other playout approaches, simulation results show that NNS achieves high-throughput and low-discontinuity playout under a variety of traffic arrivals.
Multiple access control with intelligent bandwidth allocation for wireless ATM networks
(2000-09-01)
Yuang, MC
;
Tien, PL
;
資訊工程學系
;
Department of Computer Science
Two major challenges pertaining to wireless asynchronous transfer mode (ATM) networks are the design of multiple access control (MAC), and dynamic bandwidth allocation. While the former draws more attention, the latter has been considered nontrivial and remains mostly unresolved, In this paper, we propose a new intelligent multiple access control system (IMACS) which includes a versatile MAC scheme augmented with dynamic bandwidth allocation, for wireless ATM networks. IMACS supports four types of traffic-CBR, VER, ABR, and signaling control (SCR), It aims to efficiently satisfy their diverse quality-of-service (QoS) requirements while retaining maximal network throughput. IMACS is composed of three components: multiple access controller (MACER), traffic estimator/predictor (TEP), and intelligent bandwidth allocator (IBA), MACER employs a hybrid-mode TDMA scheme, in which its contention access is based on a new dynamic-tree-splitting (DTS) collision resolution algorithm parameterized by an optimal splitting depth (SD), TEP performs periodic estimation and on-line prediction of ABR self-similar traffic characteristics based on wavelet analysis and a neural-fuzzy technique. IBA is responsible for static bandwidth allocation for CBR/VBR traffic following a closed-form formula. In cooperation with TEP, IBA governs dynamic bandwidth allocation for ABR/SCR traffic through determining the optimal SD. The optimal SD's under various traffic conditions are postulated via experimental results, and then off-line constructed using a back propagation neural network (BPNN), being used on-line by IBA, Consequently, with dynamic bandwidth allocation, IMACS offers various QoS guarantees and maximizes network throughput irrelevant to traffic variation.
Neural-network-based call admission control in ATM networks with heterogeneous arrivals
(1997-09-08)
Hah, JM
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Tien, PL
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Yuang, MC
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交大名義發表
;
資訊工程學系
Call Admission Control (CAC) has been accepted as a potential solution for supporting diverse, heterogeneous traffic sources demanding different Quality of Services (QOSs) in ATM networks. Also, CAC is required to consume a minimum of time and space to make call acceptance decisions. In this paper, we present an efficient neutral-network-based CAC (NNCAC) mechanism for ATM networks with heterogeneous arrivals. All heterogeneous traffic calls are initially categorized into various classes. Based an the number of calls in each class, NNCAC efficiently and accurately estimates the cell delay and cell loss ratio of each class in real time by means of a pre-trained neutral network. According to our decent study which exhibits the superiority of the employment of analysis-based training data over simulation-based data, we particularly construct the training data from a heterogeneous-arrival dual-class queueing model M-[N1] + I-[N2]/D/1/K, where M and I represent the Bernoulli and interrupted Bernoulli processes, and N-1 and N-2 represent the corresponding numbers of calls, respectively. Analytic results of the queueing model are confirmed by simulation results. Finally, we demonstrate the profound agreement of our neural-network-based estimated results with analytic results, justifying the viability of our NNCAC mechanism. (C) 1997 Elsevier Science B.V.
Neural-network-based call admission control in ATM networks with heterogeneous arrivals
(1996)
Hah, J
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Tien, PL
;
Yuang, MC
;
資訊工程學系
;
Department of Computer Science
Optical tunnel allocation for WDM networks with multi-granularity switching capabilities
(2003)
Lee, SSW
;
Yuang, MC
;
Tien, PL
;
Lin, SH
;
交大名義發表
For WDM networks with multi-granularity switching, Optical Tunnel Allocation (OTA) deals with the real-time establishment of optical tunnels between optical nodes through various optical multi-granularity switching devices. OTA is in principle a dynamic Routing and Wavelength Assignment (RWA) problem with multi-granularity switching devices taken into account. In this paper, we propose a novel approximation approach, called Lagrangean Relaxation with Heuristics (LRH), aimed to resolve RWA considering both fiber and lambda switches. Such RWA is first formulated as a combinatorial optimization problem in which the bottleneck link utilization is to be minimized. To tackle the problem, the LRH approach performs constraint relaxation and derives a lower-bound solution index according to a set of Lagrangean multipliers generated through subgradient-based iterations. In parallel, using the generated Lagrangean multipliers, the LRH approach employs a new heuristic algorithm to arrive at a near-optimal upper-bound solution. Through numerical results and comparisons, we delineate that the LRH approach achieves a near-optimal solution, which is profoundly tight to its lower bound, at the expense of low computational time complexity.
QoS contention control for optical coarse packet switched IP-over-WDM network
(2005)
Yuang, MC
;
Tien, PL
;
Shih, J
;
Lee, SSW
;
Lin, YM
In this paper, we first introduce an Optical Coarse Packet Switching (OCPS) paradigm. In principle, OCPS advocates the enforcement of traffic engineering and control to realize bandwidth-on-demand on sub-wavelength basis while circumventing optical packet switching limitations. Based on OCPS, we have constructed an experimental optical IP-over-WDM network testbed, referred to as OPSINET. In the paper, we present the architectural design of OPSINET and its Hybrid Contention Control (HCC) mechanism aiming to satisfy various classes of loss QoS guarantees. The mechanism preventively adopts appropriate burst sizes for different traffic classes during packet burstification at ingress routers. It also reactively performs prioritized contention resolution at OLSRs in the presence of contention. Experimental results show that HCC invariantly achieves low loss probability as a result of burstification-based traffic shaping. Moreover, it provides satisfied loss guarantees for high-priority classes while incurring minimal loss degradation for lower-priority classes.
QoS Scheduler/Shaper for optical coarse packet switching IP-over-WDM networks
(2004-11-01)
Yuang, MC
;
Tien, PL
;
Shih, J
;
Chen, A
;
資訊工程學系
For IP-over-WDM networks, optical coarse packet switching (OCPS) has been proposed to circumvent optical packet switching limitations by using in-band-controlled per-burst switching and advocating traffic control enforcement to achieve high bandwidth utilization and quality-of-service (QoS). In this paper, we first introduce the OCPS paradigm. Significantly, we present a QoS-enhanced traffic control scheme exerted during packet aggregation at ingress nodes, aiming at providing delay and loss class differentiations for OCPS networks. Serving a dual purpose, the scheme is called (psi, tau)-Scheduler/Shaper, where psi and tau are the maximum burst size and burst assembly time, respectively. To provide delay class differentiation, for IP packet flows designated with delay-associated weights, (psi, tau)-Scheduler performs packet scheduling and assembly into bursts based on their weights and a virtual window of size psi. The guaranteed delay bound for each delay class is quantified via the formal specification of a stepwise service curve. To provide loss class differentiation, (psi, tau)-Shaper facilitates traffic shaping with larger burst sizes assigned to higher loss priority classes. To examine the shaping effect on loss performance, we analytically derive the departure process of (psi, tau)-Shaper. The aggregate packet arrivals are modeled as a two-state Markov modulated Bernoulli process (MMBP) with batch arrivals. Analytical results delineate that (psi, tau)-Shaper yields substantial reduction, proportional to the burst size, in the coefficient of variation of the burst interdeparture time. Furthermore, we conduct extensive simulations on a 24-node ARPANET network to draw packet loss comparisons between OCPS and just-enough-time (JET)-based OBS. Simulation results demonstrate that, through burst size adjustment, (psi, tau)-Shaper effectively achieves differentiation of loss classes. Essentially, compared to JET-based OBS using out-of-band control and offset-time-based QoS strategy, OCPS is shown to achieve invariably superior packet loss probability for a high-priority class, facilitating better differentiation of loss traffic classes.
Threshold-based intra-video synchronization for multimedia communications
(1998-04-01)
Liang, ST
;
Tien, PL
;
Yuang, MC
;
資訊工程學系
;
Department of Computer Science
Multimedia communications often require intramedia synchronization for video data to prevent potential playout discontinuity while still retaining satisfactory playout throughput. In this paper, we propose a novel intra-video synchronization mechanism, called the Video Smoother, particularly suitable for low-end multimedia applications, such as video conferencing. Generally, the Video Smoother dynamically adopts various playout rates according to the number of frames in the playout buffer in an attempt to compensate for the delay jitter introduced from networks. In essence, if the number of frames in the buffer exceeds a given threshold (TH), the Smoother employs a maximum playout rate. Otherwise, the Smoother employs linearly or exponentially reduced rates to eliminate playout pauses resulting from the emptiness of the playout buffer. To determine optimal TH's achieving a minimum of playout discontinuity and a maximum of playout throughput under various bursty traffic, we propose an analytic model assuming incoming traffic following an Interrupted Bernoulli arrival Process (IBP). As a result, optimal TH's can be analytically determined resulting in superior playout quality under various arrivals and loads of networks. Finally, we display simulation results which demonstrate that, compared to the playout without intra-video synchronization (instant playout), the Video Smoother achieves superior smooth playout and compatible throughput.