Soomyung Park

Energy-Efficient Virtual Base Station Formation in Optical-Access-Enabled Cloud-RAN

In recent years, the increasing traffic demand in radio access networks (RANs) has led to considerable growth in the number of base stations (BSs), posing a serious scalability issue, including the energy consumption of BSs. Optical-access-enabled Cloud-RAN (CRAN) has been recently proposed as a next-generation access network. In CRAN, the digital unit (DU) of a conventional cell site is separated from the radio unit (RU) and moved to the “cloud” (DU cloud) for centralized signal processing and management. Each DU/RU pair exchanges bandwidth-intensive digitized baseband signals through an optical access network (fronthaul). Time-wavelength division multiplexing (TWDM) passive optical network (PON) is a promising fronthaul solution due to its low energy consumption and high capacity. In this paper, we propose and leverage the concept of a virtual base station (VBS), which is dynamically formed for each cell by assigning virtualized network resources, i.e., a virtualized fronthaul link connecting the DU and RU, and virtualized functional entities performing baseband processing in DU cloud. We formulate and solve the VBS formation (VF) optimization problem using an integer linear program (ILP). We propose novel energy-saving schemes exploiting VF for both the network planning stage and traffic engineering stage. Extensive simulations show that CRAN with our proposed VF schemes achieves significant energy savings compared to traditional RAN and CRAN without VF.

Green Virtual Base Station in optical-access-enabled Cloud-RAN

In recent years, the increasing traffic demand in radio access networks (RAN) has led to considerable growth of the number of base stations (BS), posing a serious scalability issue with respect to the energy consumption of BSs. Optical-access-enabled Cloud RAN (CRAN) has been recently proposed as a next-generation access network, where the digital unit (DU) of a conventional cell site is separated from the radio unit (RU), by an optical access network (fronthaul), and moved to the “cloud” (DU pool) for centralized signal processing and management. Time-Wavelength Division Multiplexing (TWDM) Passive Optical Network (PON) is a promising fronthaul solution due to its low energy consumption and high capacity. In this study, we propose the concept of Virtual Base Station (VBS), which is dynamically formed for each cell by assigning virtualized network resources, including i) a virtualized PON link connecting the DU and RU and ii) virtualized functional entities performing baseband processing in DU pool. We propose a novel energy-saving scheme exploiting VBS formation for CRAN and compare its performance with the optimal results of an Integer Linear Program for VBS formation optimization problem. Numerical evaluation shows that CRAN with VBS formation achieves significant energy savings compared to traditional RAN and CRAN without VBS formation.

Dynamic bandwidth and wavelength allocation scheme for next-generation wavelength-agile EPON

Recently, the IEEE 802.3 Ethernet Working Group has classified three architectures for the nextgeneration Ethernet passive optical network (NG-EPON). They are called single-scheduling domain (SSD) PON, multi-scheduling domain (MSD) PON, and wavelength-agile (WA) PON, and they differ based on how a group of optical network units (ONUs) share awavelength. Existing dynamic bandwidth and wavelength allocation (DBWA) schemes for conventional EPON can be applied to MSD-PON and SSDPON, but not WA-PON. This is because WA-PON is a new architecture with full flexibility where a flexible number of wavelengths can be assigned to one ONU, and multiple ONUs can transmit at the same time. In this work, we develop a mathematical model and a novel DBWA scheme for transmission scheduling in WA-PON. However, as WA-PON incurs penalties in terms of delay and power consumption when an ONU activates its transmissions on new wavelengths, a trade-off between energy saving and data-transfer latency reduction needs to be carefully addressed when performing transmission scheduling. So, we develop a power-consumption model and modify the proposed DBWA scheme to enhance the energy efficiency ofWA-PON. Finally, we conduct simulation experiments for performance evaluation of the three PON architectures in terms of latency and packet loss ratio.We quantitatively investigate the influence of various parameters, such as the number of ONU transceivers and ONU buffer size, onWA-PON latency and packet loss ratio, and we evaluate the energy efficiency gain of the modified DBWA scheme.

On the performance of Hybrid-PON scheduling strategies for NG-EPON

To effectively schedule transmissions in NG-EPON, Hybrid-PON is further classified into MSD-PON, SSD-PON, and WA-PON depending on their different access architectures, viz. how a group of ONUs share the assigned wavelength channels. The architectures for these three Hybrid-PONs were introduced by the IEEE 802.3 Ethernet Working Group in 2015. In this study, we first propose to apply some existing dynamic bandwidth allocation (DBA) schemes in the cases of MSD-PON and SSD-PON. Then, since WA-PON is a new hybrid multiplexing architecture and previous DBA schemes cannot exploit its flexibility of wavelength assignment and sharing, we develop the optimization model and also provide a novel DBA scheme for WA-PON. Then, we compare the performance of these hybrid PONs by simulation in terms of average delay and packet drop ratio. We analyze the influence of increasing buffer size for each ONU in WA-PON and show how the flexibility of WA-PON can impact the performance. We find that WA-PON can reduce the drop ratio compared with SSD-PON at low offered load, and has smaller average delay than MSD-PON, which suggest that WA-PON can tolerate heavier traffic and performs the best among three Hybrid-PON architectures.

Application-aware software-defined EPON access network

As bandwidth requirements of users in passive optical networks continue to increase rapidly, especially due to the growth of video-streaming traffic, the need to resolve bandwidth contention among competing users and applications becomes more compelling. To address this problem, we propose application-aware software-defined Ethernet passive optical network (EPON) architecture. It utilizes application-level feedback from the client side (for video users) to the network, through a software-defined network controller, to achieve better client- and service-level differentiation in the downstream direction of an EPON access network. We adopt adaptive video streaming that utilizes feedbacks regarding network congestion for improving Quality of Experience (QoE) of video-streaming clients. Numerical results for video-streaming applications demonstrate that the proposed architecture for downstream resource allocation considerably reduces video stalls, increases video buffer levels, and also reduces video-switching rate, leading to better QoE for users as a result of better client- and service-level differentiation.

Orchestration for multiple domain transport networks

ETRI distributed cloud platform provides customers with optimal computing and storage resources over remotely distributed micro datacenters connected over multi-domain transport networks. It requires dynamic SDN control to utilize transport network resource efficiently. This paper introduces implementation of transport network orchestration to control multi-domain transport networks for the distributed cloud platform.

QoE enhancement schemes for video in converged OFDMA wireless networks and EPONS

Bandwidth requirements of both wireless and wired clients in access networks continue to increase rapidly, primarily due to the growth of video traffic. Application awareness can be utilized in access networks to optimize quality of experience (QoE) of end clients. In this study, we utilize information at the client-side application (e.g., video resolution) to achieve superior resource allocation that improves user QoE. We emphasize optimizing QoE of the system rather than quality of service (QoS), as user satisfaction directly relies on QoE and optimizing QoS does not necessarily optimize QoE, as shown in this study. We propose application-aware resource-allocation schemes on an Ethernet passive optical network (EPON), which supports wireless (utilizing orthogonal frequency division multiple access) and wired clients running video-conference applications. Numerical results show that the application-aware resource-allocation schemes improve QoE for video-conference applications for wired and wireless clients.

OXC management and control system architecture with scalability, maintenance, and distributed managing environment

In this paper, we present the Optical Cross-Connect (OXC) Management Control System Architecture, which has the scalability and robust maintenance and provides the distributed managing environment in the optical transport network. The OXC system we are developing, which is divided into the hardware and the internal and external software for the OXC system, is made up the OXC subsystem with the Optical Transport Network (OTN) sub layers-hardware and the optical switch control system, the signaling control protocol subsystem performing the User-to-Network Interface (UNI) and Network-to-Network Interface (NNI) signaling control, the Operation Administration Maintenance & Provisioning (OAM&P) subsystem, and the network management subsystem. And the OXC management control system has the features that can support the flexible expansion of the optical transport network, provide the connectivity to heterogeneous external network elements, be added or deleted without interrupting OAM&P services, be remotely operated, provide the global view and detail information for network planner and operator, and have Common Object Request Broker Architecture (CORBA) based the open system architecture adding and deleting the intelligent service networking functions easily in future. To meet these considerations, we adopt the object oriented development method in the whole developing steps of the system analysis, design, and implementation to build the OXC management control system with the scalability, the maintenance, and the distributed managing environment. As a consequently, the componentification for the OXC operation management functions of each subsystem makes the robust maintenance, and increases code reusability. Also, the component based OXC management control system architecture will have the flexibility and scalability in nature.