International Standards published by Broadband Forum to Achieve Modularization of Dynamic Bandwidth Assignment; A Crucial Function to QoS in Optical Access System

Broadband Forum ("BBF*1") which is an industry organization focusing on engineering smarter and faster broadband networks approved standards about modularization of dynamic bandwidth assignment (DBA*2) function on December 3, 2018, which represents a significant impact on quality of service (QoS) in an optical access system. These standards specify an API*3 (Application Programming Interface), which enables the replacement of the DBA software module, to realize future optical access systems that can quickly and cost-effectively provide the widest possible range of services.
Nippon Telegraph and Telephone Corporation (NTT) and Chunghwa Telecom have jointly proposed use cases of the DBA software module at BBF meetings, and developed the API specifications as the international standards. This advance enables carriers to use a common access system for a diverse range of services including accommodation of base stations for the fifth generation (5G) and beyond 5G mobile systems, which strictly require low latency.
NTT will promote the developed standards, and push forward its R&D activities which are even now contributing to the expansion of the application area of optical access systems in cooperation with other carriers, system vendors, standardization organizations (SDO), and open source software (OSS) development organizations.

Background

In 2016, NTT launched the new concept of FASA*4 (Flexible Access System Architecture) with the target being the technology to realize the access network of the future. Since then, NTT has conducted R&D activities on primary technologies and specifications. Meanwhile, BBF has intensively developed new architectures, interfaces, and protocols which enable disaggregation of functions composing access systems. In 2018, NTT succeeded in modularization by dividing it into a software part that is replaced to suit the service requirements, and a hardware part independent from the requirements, although DBA is well known to be one of the most difficult functions to modularize because of its timing-critical feature*5,6. NTT also succeeded in developing and testing OLT prototypes with the API that enables the smooth replacement of DBA software modules, and in demonstration, for the first time, that the DBA software can be replaced to meet new service requirements.

International standard for modularization of DBA

NTT launched a new project stream (PON Abstraction Interface for Time-critical Applications) at BBF in Oct. 2016 with the intention of defining the API, which can be used in common with various partners. Based on the expertise gained from the prototype development, NTT has been addressing with the carriers and vendors to establish an international standard of the API specifications.
The newly published BBF international standard on the API consists of two Technical Reports (TR) -402 and 403 (Table 1). TR-402 provides an overview of the modularization of the DBA function including a use case regarding accommodation of base stations for the fifth generation (5G) and beyond 5G mobile systems over an optical access network, and specifies the functional requirements of the API. In TR-403, the details of the API (format and performance requirements) were specified.
Although the DBA, which requires high-speed processing in the order of sub-milliseconds, had been difficult to modularize, it is a crucial function that represents a significant impact on QoS in an optical access system. NTT believes that the widespread use of the API as an international standard will lead to the drastic expansion of the application area of optical access systems

Figure 1 Replacement of softwarized DBA functions to meet each service requirements.

Table 1 List of newly developed BBF standards

Looking forward

In addition to this international standard of API specifications, NTT will pursue to modularize the remaining access functions in cooperation with carriers, system vendors, SDOs, and OSS organizations in order to avoid the significant investment of redeveloping hardware-level equipment from scratch. This will result in cost-effective access systems that can quickly meet various requirements.

Terminology

Attachments / References

Figure 1：Replacement of softwarized DBA functions to meet each service requirement.

Table 1：List of newly developed BBF standards

FASA is a registered trademark of NTT.