Feature Articles: Network Technology for Digital Society of the Future—Research and Development of Competitive Network Infrastructure Technologies

FASA®: New Access System Architecture

Takamitsu Tochino, Keita Nishimoto, Tomoya Hatano,
Kota Asaka, Jun-ichi Kani, and Jun Terada

Abstract

NTT Access Network Service Systems Laboratories has been promoting new access system architecture called FASA® (Flexible Access System Architecture), and researching and developing the modularization of functions making up the access system. This article introduces the technology behind the software modularization of the dynamic bandwidth allocation function, which was announced in a press release in November 2018 and demonstrated for the first time at NTT R&D Forum 2018 Autumn.

Keywords: FASA, access system, DBA

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1. Introduction

NTT Access Network Service Systems Laboratories has been researching and developing FASA®*1 (Flexible Access System Architecture) as the optical access system of the future since it announced the concept in February 2016 [1, 2]. FASA reflects the research and development (R&D) of competitive network infrastructure technologies that enable the functions making up the access system to be extensively modularized and combined as needed. The aim here is to achieve an optical access system that can replace functions in a flexible and rapid manner according to service requirements.

The access system in widely used passive optical network (PON) systems has a point-to-multipoint network configuration on which users share a single optical fiber and bandwidth via fiber splitters. Here, the function that governs the performance of a PON system is dynamic bandwidth allocation (DBA), which, as the name implies, allocates bandwidth dynamically according to user bandwidth requirements.

At NTT Access Network Service Systems Laboratories, we considered that the optical access system could be applied to a wide array of services if the DBA function in a PON system could be replaced as needed. With this in mind, we conducted R&D and established software modularization technology for the DBA function, proposed two optical line terminal (OLT) models capable of incorporating the function, and enabled both OLT models to accommodate the softwarized DBA function (Fig. 1).


Fig. 1. Replacement of softwarized DBA function to meet service requirements.

*1 FASA is a registered trademark of Nippon Telegraph and Telephone Corporation in Japan.

2. Software modularization technology for DBA function

The DBA function must be capable of high-speed processing on the sub-millisecond order to allocate bandwidth to each user according to fluctuating bandwidth requirements. To enable function replacement as needed while maintaining high-speed processing, we modularized the DBA function into a high-speed processing section and an algorithm whose specifications would differ for each service and implemented the former as hardware and the latter as software. We also defined the interface between the software and hardware components as an application programming interface (API)*2 and promoted its standardization at the Broadband Forum industry organization, which completed the process in 2018.

As a result, the DBA function can be replaced as needed according to service requirements while achieving high-speed processing.

*2 API: Interface specifications for exchanging information between two components.

3. Two OLT models and API implementation

We defined two OLT models to enable a PON system to be used in a variety of applications and developed a prototype OLT of each model for evaluation.

The first model is a box-type OLT for use in environments such as a telecommunication carrier’s exchange office. We expect it to be applied to future mobile systems in addition to existing FTTH (fiber-to-the-home) services. The second model is a module-type OLT, which is implemented only for OLT functions that must be processed by hardware in a compact module in combination with a commodity server that stores the OLT functions modularized in software. We expect this type of OLT to be applied to factories and local area networks on university campuses, and in office buildings and other such settings.

In either of these OLT models, the incorporation of an API enables the DBA function to be replaced with another one according to the application. This scheme eliminates the need for extensive equipment upgrading at the hardware level according to service requirements and enables the application range of optical access systems to be expanded.

4. Future plan

Going forward, the team at NTT Access Network Service Systems Laboratories plans to pursue software modularization for functions other than the DBA function in cooperation with carrier system vendors, standardization bodies, and open source software organizations throughout the world. The goal here is to enable the optical access system to be applied to a wide variety of services.

References

[1] Press release issued by NTT, “Introducing the New FASA Concept for Future Access Systems,” Feb. 8, 2016.
http://www.ntt.co.jp/news2016/1602e/160208a.html
[2] FASA home page,
http://www.ansl.ntt.co.jp/e/global/FASA/index.html
Takamitsu Tochino
Research Engineer, Optical Access Systems Project, NTT Access Network Service Systems Laboratories.
He received a B.E. and M.E. in physics and electronics from Osaka Prefecture University in 2014 and 2016. He joined NTT Access Network Service Systems Laboratories in 2016. He is involved in R&D of optical communications systems and network virtualization.
Keita Nishimoto
Research Engineer, Optical Access Systems Project, NTT Access Network Service Systems Laboratories.
He received a B.E. from Doshisha University, Kyoto, in 2012 and a Master of Information Science from Nagoya University in 2014. Since joining NTT Access Network Service Systems Laboratories in 2014, he has engaged in R&D of virtual optical access networks including FASA. From 2018 to 2019, he was involved with the development of SEBA (SDN (software-defined networking)-Enabled Broadband Access) in the Open Networking Foundation.
Tomoya Hatano
Senior Research Engineer, Optical Access Systems Project, NTT Access Network Service Systems Laboratories.
He received a B.E., M.E., and Ph.D. from Keio University, Tokyo, in 2002, 2004, and 2007. He joined NTT Access Network Service Systems Laboratories in 2004. He is currently researching and developing optical communications systems and network virtualization.
Kota Asaka
Senior Research Engineer, Optical Access Systems Project, NTT Access Network Service Systems Laboratories.
He received a B.S. and M.S. in electrical engineering from Waseda University, Tokyo, in 1996 and 1999, and a Ph.D. in physics from Kitasato University, Tokyo, in 2008. He joined NTT Photonics Laboratories in 1999, where he researched photonics integrated circuits and low-cost and small optical subassemblies for access networks. From 2009 to 2012, he served as the Working Group (WG) secretary of IEC (International Electrotechnical Commission) Subcommittee 86C/WG4 for standardization of fiber optic active components. He has been with NTT Access Network Service Systems Laboratories since 2012, where he is engaged in R&D related to next-generation optical access networks such as Next-Generation Passive Optical Network Stage 2, OFDM (orthogonal frequency division multiplexing)-PON, and SDN/NFV (network functions virtualization). He has been participating in International Telecommunication Union - Telecommunication Standardization Sector (ITU-T)/Full Service Access Network (FSAN) since 2012 as well as the Broadband Forum since 2016. Dr. Asaka is a member of IEEE (Institute of Electrical and Electronics Engineers) Communications Society, and the Institute of Electronics, Information and Communication Engineers (IEICE) of Japan.
Jun-ichi Kani
Senior Research Engineer, Supervisor (Distinguished Researcher), Group Leader, Optical Access Systems Project, NTT Access Network Service Systems Laboratories.
He received a B.E., M.E., and Ph.D. in applied physics from Waseda University, Tokyo, in 1994, 1996, and 2005. He joined NTT Optical Network Systems Laboratories in 1996, where he researched optical multiplexing and transmission technologies. He has been with NTT Access Network Service Systems Laboratories since 2003, where he is engaged in R&D of optical communications systems for metropolitan and access network applications and currently heads the Access Systems Technology Group. He has been participating in ITU-T and the FSAN initiative since 2003.
Jun Terada
General Manager, NTT Access Network Service Systems Laboratories.
He received a B.E. in science and engineering and an M.E. in computer science from Keio University, Kanagawa, in 1993 and 1995. He joined NTT LSI Laboratories in 1995, where he researched low-voltage analog circuits, especially analog-to-digital and digital-to-analog converters. He has also been involved in developing small and low-power wireless systems for sensor networks and high-speed front-end circuits for optical transceivers. He is currently responsible for R&D management of optical access networks including fixed-wireless convergence and virtualization technology. He is a senior member of IEICE. He also serves as a technical committee member of the Asian Solid-State Circuits Conference (A-SSCC) and as the vice chair of the IEICE Technical Committee on Communication Systems.

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