Sunhee Yang

Bio: Sunhee Yang is an academic researcher. The author has contributed to research in topics: Passive optical network & Quality of service. The author has an hindex of 3, co-authored 3 publications receiving 533 citations.

Wavelength-division-multiplexed passive optical network (WDM-PON) technologies for broadband access: a review (Invited)

Abstract: Feature Issue on Optical Access Networks (OAN) The passive optical network (PON) is an optical fiber based network architecture, which can provide much higher bandwidth in the access network compared to traditional copper-based networks. Incorporating wavelength-division multiplexing (WDM) in a PON allows one to support much higher bandwidth compared to the standard PON, which operates in the "single-wavelength mode" where one wavelength is used for upstream transmission and a separate one is used for downstream transmission. We present a comprehensive review of various aspects of WDM-PONs proposed in the literature. This includes enabling device technologies for WDM-PONs and network architectures, as well as the corresponding protocols and services that may be deployed on a WDM-PON. The WDM-PON will become a revolutionary and scalable broadband access technology that will provide high bandwidth to end users.

Shared-wavelength WDM-PON access network for supporting downstream traffic with QoS

Abstract: We propose a novel shared-wavelength WDM-PON architecture to accommodate downstream bursty traffic, and provide architectural support for different QoS to users. Downstream wavelength-allocation algorithm is proposed and its properties are evaluated.

SLA-Aware Protocol for Efficient Tunable Laser Utilization to Support Incremental Upgrade in Long-Reach Passive Optical Networks

Abstract: With the advances in optical technology, the span of a broadband access network using passive optical network (PON) technology can be increased from today's standard of 20 km to 100 km or higher and thereby serve many more users. Such an extended-reach PON is known as a SuperPON in the literature, and we call it a long-reach PON (LR-PON). A major challenge in LR-PON is how to utilize the network resources (e.g., wavelengths, lasers, etc.) effectively to meet the increased bandwidth requests from the expanding base of users. We propose a new and efficient protocol to achieve a high utilization of tunable lasers across different user groups in LR-PON. To accommodate downstream bursty traffic and provide quality of service in the user-specified service-level agreements (SLAs), the protocol integrates our proposed SLA-aware bandwidth allocation scheme based on flow scheduling. Illustrative numerical results demonstrate the protocol's advantage to support incremental upgrade of bandwidth with increasing user bandwidth requests and to provide a user with an SLA that guarantees a number of streaming flows with average bandwidth and maximum delay guarantee (i.e., 5 ms), as well as data flows with average bandwidth specifications.

OFDM for Next-Generation Optical Access Networks

Abstract: In this tutorial overview, the principles, advantages, challenges, and practical requirements of optical orthogonal frequency division multiplexing (OFDM)-based optical access are presented, with an emphasis on orthogonal frequency division multiple access (OFDMA) for application in next-generation passive optical networks (PON). General OFDM principles, including orthogonality, cyclic prefix use, frequency-domain equalization, and multiuser OFDMA are summarized, followed by an overview of various optical OFDM(A) transceiver architectures for next-generation PON. Functional requirements are outlined for high-speed digital signal processors (DSP) and data converters in OFDMA-PON. A techno-economic outlook for such a “software-defined,” DSP-based optical access platform is also provided.

Hybrid Wireless-Optical Broadband-Access Network (WOBAN): A Review of Relevant Challenges

Abstract: The hybrid wireless-optical broadband-access network (WOBAN) is a promising architecture for future access networks. Recently, the wireless part of WOBAN has been gaining increasing attention, and early versions are being deployed as municipal access solutions to eliminate the wired drop to every wireless router at customer premises. This architecture saves on network deployment cost because the fiber need not penetrate each end-user, and it extends the reach of emerging optical-access solutions, such as passive optical networks. This paper first presents an architecture and a vision for the WOBAN and articulates why the combination of wireless and optical presents a compelling solution that optimizes the best of both worlds. While this discussion briefly touches upon the business drivers, the main arguments are based on technical and deployment considerations. Consequently, the rest of this paper reviews a variety of relevant research challenges, namely, network setup, network connectivity, and fault-tolerant behavior of the WOBAN. In the network setup, we review the design of a WOBAN where the back end is a wired optical network, the front end is managed by a wireless connectivity, and, in between, the tail ends of the optical part [known as optical network unit (ONU)] communicate directly with wireless base stations (known as ldquogateway routersrdquo). We outline algorithms to optimize the placement of ONUs in a WOBAN and report on a survey that we conducted on the distribution and types of wireless routers in the Wildhorse residential neighborhood of North Davis, CA. Then, we examine the WOBAN's routing properties (network connectivity), discuss the pros and cons of various routing algorithms, and summarize the idea behind fault-tolerant design of such hybrid networks.

PON in adolescence: from TDMA to WDM-PON

Abstract: Passive optical networks are used for fiber-to-the-home/curb/cabinet/building applications. Today, two PON variants with time-domain multiple access, GPON and EPON, are being used for mass roll-outs. WDM-PONs are the next step up from these PONs to accommodate traffic growth and new applications. This article analyzes WDM-PON variants and proposes they be used for a unified optical access and back-hauling network.

Long-reach optical access networks: A survey of research challenges, demonstrations, and bandwidth assignment mechanisms

Abstract: Long-Reach optical access is a promising proposal for future access networks. This technology can enable broadband access for a large number of customers in the access/metro area, while decreasing capital and operational expenditures for the network operator. First, the paper reviews the evolutionary path of access networks and shows the drivers from technology and business perspectives for high bandwidth and low cost. A variety of research challenges in this field is reviewed, from optical components in the physical layer to the control and management issues in the upper layers. We discuss the requisites for optical sources, optical amplifiers, and optical receivers when used in networks with high transmission rate (10 Gbps) and large power attenuation (due to large split, transmission over 100 km and beyond, and propagation), and the key topological structures that allow to guarantee physical protection (tree-and-branch, ring-and-spur). Then, some relevant demonstrations of Long-Reach Optical Access Networks developed worldwide by different research institutes are presented. Finally, Dynamic Bandwidth Allocation (DBA) algorithms that allow to mitigate the effect of the increased control-plane delay in an extended-reach network are investigated.

Dynamic Wavelength and Bandwidth Allocation in Hybrid TDM/WDM EPON Networks

Abstract: We discuss a wavelength-division-multiplexed-based passive-optical-network (PON) architecture that allows for incremental upgrade from single-channel time-division multiple-access PONs in order to provide higher bandwidth in the access network. Various dynamic-wavelength and bandwidth-allocation algorithms (DWBAs) for wave-division multiplexed PON are presented; they exploit both interchannel and intrachannel statistical multiplexing in order to achieve better performance, especially when the load on various channels is not symmetric. Three variants of the DWBA are presented, and their performance is compared. While the first variant incurs larger idle times (and, hence, poor performance), the other two algorithms achieve better but different performance with critical dissimilarities. Our analysis also focuses on the fair assignment of excessive bandwidth in the upstream direction to highly loaded optical network units. We compare the performance of DWBA to another algorithm that relies on static-channel allocation. Furthermore, a study is presented wherein the number of wavelengths increases, and a comparison with interleaved polling with adaptive cycle time is shown. We use extensive simulations throughout this paper