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ABSTRACT: In this paper, we propose a novel architecture for next-generation orthogonal frequency division multiple access (OFDMA)-based passive optical networks (PON's), referred to as ROFPON. Besides carrying local broadband OFDMA data, ROFPON seamlessly supports radio-over-fiber (RoF) transports between the central office and multiple remote antennas at end users without using costly WDM lasers. We analytically and experimentally study the receiver sensitivity to OFDMA signals and the radio frequency (RF) signal's performance. By corroborating simulation results with experimental results, we discuss the determination of crucial system parameters, such as the optimal broadband-to-radio power ratio, and the exploitation of a notch filter for removing RF interference. Experimental results show that the integrated 10 Gb/s OFDMA and three 20 MHz RF signals are successfully transported both downstream and upstream over a 20 km single-mode-fiber PON. Finally, experimental results demonstrate that QPSK-encoded WiMAX format RF signals are transmitted/relayed upstream with E-O-E conversion at each optical network unit (ONU), and received error-free at the optical line terminal after cascading 32 ONU's.
IEEE Journal on Selected Areas in Communications 09/2010; · 3.41 Impact Factor
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ABSTRACT: Optical packet switching has been considered a prominent paradigm for future WDM networks to efficiently support a multitude of applications with diverse quality of service requirements. In this article we present the architectural design and experimental demonstration of a 10 Gb/s QoS optical packet switching system (QOPSS) for WDM networks. It embodies a set of many-to-one space switches, each of which handles the switching solely for a cluster of wavelengths. With the cluster-based optical switch design, QOPSS trades off limited statistical multiplexing gains for higher system scalability. By many-to-one, multiple packets that are carried by different internal wavelengths are scheduled to switch to the same output port but receive different delays afterward. QOPSS adopts downsized feed-forward optical buffers, yielding drastic reduction in packet loss probability in an economical manner. Significantly, through using four-wave-mixing wavelength converters at the output section, QOPSS permits optical packet preemption, thus achieving effectual QoS differentiation. The article presents both simulation and experimental testbed results to demonstrate the feasibility and superior packet loss/QoS performance of the system.
IEEE Communications Magazine 06/2010; · 3.79 Impact Factor
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ABSTRACT: In this letter, we propose a novel passive optical network (PON) architecture supporting radio-over-fiber signals and orthogonal frequency-division multiple access (OFDMA) PON signals. The architecture transports upstream multiple remote antenna's wireless signals using only one upstream wavelength. In addition, the windowed-orthogonal frequency-division-multiplexing technique is employed to mitigate interference during the integration process. Experimental results shows that 10-Gb/s OFDMA and three radio-frequency signals at 2.1 GHz are successfully transmitted over 20-km single-mode fiber in a 32-optical-network-unit PON.
IEEE Photonics Technology Letters 04/2010; · 2.19 Impact Factor
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IEEE Journal on Selected Areas in Communications. 01/2010; 28:791-799.
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IEEE Communications Magazine. 01/2010; 48:66-75.
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ABSTRACT: We present a novel PON architecture supporting RoF and OFDMA signal integration without WDM lasers, and demonstrate 10-Gb/s OFDMA and three RF signals at 2.1 GHz are successfully transmitted over 20 km SMF in a 32-ONU PON.
Optical Communication, 2009. ECOC '09. 35th European Conference on; 10/2009
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ABSTRACT: We present a novel pseudo-Banyan optical packet switching system (SBOPSS) for optical wavelength division multiplexing (WDM) networks. The system includes a group of pseudo-Banyan space switches together with single-stage downsized fiber-delay-line-based optical buffers. SBOPSS is scalable, with the result that each pseudo-Banyan space switch performs packet switching only for a cluster of wavelengths. The downsized optical buffers that are shared by output ports via the use of a small number of internal wavelengths result in efficient reduction in packet loss. Essentially, SBOPSS employs a packet scheduling algorithm, referred to as the parallel and incremental packet scheduler (PIPS). Given a set of newly arriving packets per time slot, PIPS determines a maximum number of valid paths (packets) to be scheduled with the current bufferspsila state taken into account. The algorithm aims at maximizing the system throughput subject to satisfying three constraints, which are switch-contention free, buffer-contention free, and sequential delivery. Significantly, we prove that PIPS is incremental in the sense that the computed-path sets are monotonically nondecreasing over time. We then propose a hardware parallel system architecture for the implementation of PIPS. As is shown, PIPS achieves a near-optimal solution with an exceptionally low computational complexity, O(IPItimeslog<sub>2</sub>(NMW)), where P is the newly-arriving-packet set, N the number of input ports, and M and W the numbers of internal and external wavelengths, respectively. From simulation results that pit the PIPS algorithm against four other algorithms, we show that PIPS outperforms these algorithms on both system throughput and computational complexity.
Journal of Optical Communications and Networking 09/2009; · 1.87 Impact Factor
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ABSTRACT: In this paper, we present the access and control design of a high-performance optical packet-switched WDM metro ring network (HOPSMAN). HOPSMAN has been designed for networks and nodes to be unconstrained by the number of wavelengths. It includes a handful of nodes that are equipped with fast optical slot erasers making bandwidth reusable and achieving greater bandwidth efficiency. In essence, HOPSMAN incorporates a versatile medium access control (MAC) scheme, which embodies efficient and fair bandwidth allocation in accordance with a quota being exerted probabilistically. The quota is analytically derived with the number of slot-eraser-nodes taken into account. The scheme also employs a new notion of credit to regulate flexible access of remaining bandwidth that is suitable for the metro environment with bursty traffic. With the MAC scheme, HOPSMAN is shown to achieve exceptional throughput, delay, and fairness performance under a wide range of traffic settings via simulation results.
Global Telecommunications Conference, 2008. IEEE GLOBECOM 2008. IEEE; 01/2009
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ABSTRACT: For future WDM MANs, optical packet-switching has been considered to be a promising paradigm that efficiently supports a wide range of Internet-based applications having time-varying and high bandwidth demands and stringent delay requirements. This article presents the design of an experimental testbed system for a high-performance optical packet-switched WDM metro ring network, HOPSMAN. HOPSMAN boasts three crucial features. First, it has a scalable architecture in which the number of nodes is unconstrained by the number of wavelengths. Second, HOPSMAN nodes are equipped with high-speed photonic hardware components, including fast tunable receivers and optical slot erasers, capable of performing speedy optical packet-switching operations. Third, HOPSMAN incorporates a MAC scheme that embodies efficient and dynamic bandwidth allocation, resulting in exceptional delay-throughput performance. The article presents the key hardware components by highlighting the challenging issues we faced and the solutions we proposed for the testbed implementation. Finally, to demonstrate the feasibility of HOPSMAN, the article describes the experimental setup and presents the results obtained from running a commercially available remote media player application on the system.
IEEE Communications Magazine 08/2008; · 3.79 Impact Factor
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ABSTRACT: Optical Packet Switching (OPS) has been envisioned as a prominent future optical networking technology for datacentric IP over Wavelength Division Multiplexing (WDM) networks, or optical Internet. Such OPS technology however raises significant transport and Quality of Service (QoS) challenges due to technological limitations. To circumvent OPS limitations, we have proposed a new Optical Coarse Packet Switching (OCPS) paradigm, which uses in-band-controlled per-burst switching and advocates traffic control enforcement to achieve high packet-loss performance and differentiated services. Based on OCPS, we have constructed an experimental IP-over-WDM network, referred to as OPSINET. OPSINET consists of two major types of nodes-edge routers, and Optical Label Switched Routers (OLSRs), and is facilitated with an out-of-band Generalized Multi-protocol Label Switching (GMPLS) control network. In this paper, we first introduce the OCPS paradigm. We then present the architecture of OPSINET, describe the in-band header/payload modulation technique, and detail the operations of the edge routers, OLSRs, and GMPLS control
IEEE Journal on Selected Areas in Communications 09/2006; · 3.41 Impact Factor
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ABSTRACT: 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.
Information Technology: Research and Education, 2005. ITRE 2005. 3rd International Conference on; 07/2005
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ABSTRACT: 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.
IEEE Journal on Selected Areas in Communications 12/2004; · 3.41 Impact Factor
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ABSTRACT: 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 (ψ,τ)-Scheduler/Shaper, where ψ and τ are the maximum burst size and burst assembly time, respectively. To provide delay class differentiation, for IP packet flows designated with delay-associated weights, (ψ,τ)-Scheduler performs packet scheduling and assembly into bursts based on their weights and a virtual window of size ψ. The guaranteed delay bound for each delay class is quantified via the formal specification of a stepwise service curve. To provide loss class differentiation, (ψ,τ)-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 (ψ,τ)-Shaper. The aggregate packet arrivals are modeled as a two-state Markov modulated Bernoulli process (MMBP) with batch arrivals. Analytical results delineate that (ψ,τ)-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, (ψ,τ)-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.
IEEE Journal on Selected Areas in Communications 12/2004; · 3.41 Impact Factor
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ABSTRACT: 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.
Global Telecommunications Conference, 2003. GLOBECOM '03. IEEE; 01/2004
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ABSTRACT: Prevailing weight-based scheduling algorithms advocate static or coarse-grained simplification of timestamp computation, resulting in performance bottlenecks and unnecessary downgrades 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 θ<sub>min</sub>-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≤10), SQS outperforms weighted fair queueing (WFQ) and performs as superior as worst-case fair weighted fair queueing (WF<sup>2</sup>Q) with respect to throughput fairness, mean delay, and worst-case delay fairness.
Communications, 2002. ICC 2002. IEEE International Conference on; 02/2002
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ABSTRACT: In this paper, we propose an efficient approximation approach, called Lagrangean relaxation with heuristics (LRH), aimed to resolve routing and wavelength assignment (RWA) for multi-granularity WDM networks facilitating fiber, waveband, and lambda switching capabilities. 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 delineate the performance of LRH with respect to accuracy and convergence speed under different parameter settings. We further draw comparisons between LRH and a typical linear programming (LP) approach via experiments over the widely-used NSFNET and three randomly generated networks. Numerical results demonstrate that LRH outperforms the LP approach in both accuracy and computational time complexity particularly for larger sized networks.
Global Telecommunications Conference, 2004. GLOBECOM '04. IEEE;
