Julin Shih

A High-Performance OFDMA PON System Architecture and Medium Access Control

Orthogonal frequency-division multiplexing (OFDM) passive optical network (PON) has been considered to be a promising next-generation broadband wired access solution. However, based on the current tree-based architecture, existing OFDM PON systems face severe challenges when increasing the scalability and data-rate performance. In this paper, we propose a high-performance virtual-tree orthogonal frequency-division multiple access PON system (VTOPS). With the virtual-tree architecture and coupled with the use of inexpensive direct modulation, VTOPS features high reliability, scalability, spectrum efficiency, and cost effectiveness all at once. For governing the flexible/fair access and dynamic allocation of bandwidth, VTOPS incorporates a rate-based medium access control (MAC) scheme. The MAC scheme performs dynamic rate adjustment using a neural-fuzzy system. By adjusting the system parameters, the MAC scheme can achieve a wide range of delay and fairness performance under a variety of traffic patterns. Finally, we show both theoretical and experimental results to demonstrate that, by applying the power pre-emphasis algorithm and adaptive subchannel modulation, VTOPS achieves 40 Gb/s downlink and 40 Gb/s uplink transmissions, using low-cost 10 GHz directly modulated lasers.

QoS burstification for optical burst switched WDM networks

In this paper, we propose a QoS burstification (QBT) mechanism on the basis of a new notion window. The QBT mechanism efficiently emulates the burst behavior by exerting simple FIFO service within the window and weight-proportional service at the window boundary. As will be shown, QBT achieves fairness and mean-burstification-delay guarantees among various traffic classes.

A 40-Gb/s OFDM PON System Based on 10-GHz EAM and 10-GHz Direct-Detection PIN

This letter demonstrates a 40-Gb/s optical double-sideband (ODSB) orthogonal frequency-division multiplexing passive optical network (OFDM-PON) system using a cost-effective 10-GHz-bandwidth electroabsorption modulator (EAM). By employing a subcarrier-adaptive modulation format and pre-emphasis, we successfully achieve 20-km EAM-based single-mode-fiber (SMF) transmission.

QoS scheduler/shaper for optical coarse packet switching IP-over-WDM networks

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 (/spl psi/,/spl tau/)-Scheduler/Shaper, where /spl psi/ and /spl 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, (/spl psi/,/spl tau/)-Scheduler performs packet scheduling and assembly into bursts based on their weights and a virtual window of size /spl 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, (/spl psi/,/spl 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 (/spl psi/,/spl tau/)-Shaper. The aggregate packet arrivals are modeled as a two-state Markov modulated Bernoulli process (MMBP) with batch arrivals. Analytical results delineate that (/spl psi/,/spl 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, (/spl psi/,/spl 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.

A Novel Passive Optical Network Architecture Supporting Seamless Integration of RoF and OFDMA Signals

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 antennas 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.

A QoS optical packet switching system: architectural design and experimental demonstration [Topics in Optical Communications]

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.

A virtual-tree OFDMA PON system architecture

OFDM PON has been considered to be one of the most prominent next-generation broadband wired access solutions. However, based on the current tree-architecture, existing OFDM PON systems face severe challenges when increasing the scalability and data-rate performance. In this paper, we propose a novel virtual-tree architecture of an OFDMA PON system (VTOPS). Coupled with the use of inexpensive direct modulation, VTOPS simultaneously achieves high reliability, scalability, and spectrum efficiency (i.e., high data rate) in a cost-effective manner. Theoretical and experimental results demonstrate that, by applying the pre-emphasis algorithm and subchannel adaptive modulation, VTOPS achieves 40-Gb/s downlink and uplink transmissions using low-cost 10-GHz directly modulated lasers.

Optical coarse packet-switched IP-over-WDM network (OPSINET): technologies and experiments

Optical Packet Switching (OPS) has been envisioned as a prominent future optical networking technology for data-centric 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 bandwidth utilization and Quality-of-Service (QoS). 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). 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 and OLSRs.

gama-TBSC: Time-Bound Signaling Control with gama-Percent Soft Guarantee in IEEE 802.11 Wireless LANs

Signaling control schemes for wireless multimedia services are expected to maximize the number of newly-accepted mobile terminals (MTs), i.e., system throughput, while maintaining the quality of service (QoS) requirements for the existing MTs in the system. In this paper, we propose a γ-percent time-bound signaling control (γ-TBSC) scheme that resolves a maximum number of MTs mostly within a given bounded time, subject to assuring γ-percent soft guarantee for existing MTs. The γ-TBSC scheme performs signaling control in two phases: the call-invitation phase, and the contention-resolution phase. In the first phase, an access point invites a number of so-called potential MTs to make reservations during a call invitation interval (CII). If any collision occurs, γ-TBSC performs contention resolution in the second phase until all potential MTs are resolved successfully. Most importantly, prior to the two-phase operation, γ-TBSC analytically and statistically determines the potential MT number and the CII length such that the system throughput is maximized and the QoS is soft guaranteed. From simulation results that pit γ-TBSC against several variants of carrier sense multiple access with collision avoidance (CSMA/CA) schemes, we delineate that γ-TBSC outperforms these schemes with respect to throughput and delay performance.

A 10G QoS-enabled optical packet-switching system: technology and experimentation

The paper presents the architecture and experimentation of a 10-Gb/s QoS-enabled almost-all-optical packet switching system (QOPS) for metro WDM networks. By applying cluster-based wavelength sharing and downsized single-staged optical buffers, QOPS is featured by its highly scalable and cost-effective design. In this paper, we first introduce the switch architecture, system operation, and the key techniques. We describe the in-band header/payload modulation and optical label swapping that is suitable for high-speed optical packet switching. We also present the design of the highly efficient Four-Wave Mixing wavelength converters for packet preemption. We then present an adaptive bifurcated routing (ABR) that directs same-connection packets to different switch clusters according to optimal bifurcation probabilities. Experimental and simulation results demonstrate that QOPS can achieve superior packet-loss performance, QoS differentiation, and minimize traffic blocking probability.