As we seek to provide standards for integration with a growing range of 'vertical' business sectors, 3GPP has initiated a new area of API specification work.
At our March 2017 Plenary meeting (SA#75) a new Study onCommon API Framework for 3GPP Northbound APIswas approved and now the SA6 Working Group – responsible for application layer functional elements and interfaces - has started investigating the topic.
In order to provide mobile end-to-end services, 3GPP interfaces exist throughout the system:
Between the mobile device and the Radio Network;
Between the Radio Network and the packet core network;
Within the core network;
To external networks;
For management and orchestration, etc.
These interfaces have facilitated the development of a range of diverse equipment, providing a broad range of functionality and services.
Providing a broader range of standardized services with a wide range of partners has been a goal from the earliest days of 3GPP.
An area where 3GPP has not actively developed standards to achieve this goal is at the 'Northbound Application Programmer Interface' level, since the transfer of the Open Service Architecture (OSA) API work to the Open Mobile Alliance (OMA), in 2008.
A Northbound API is an interface between an Application Server (either in a mobile operator's network or external to it - operated by a third party) and the 3GPP system via specified Functions in a mobile operator's network.
The new SA6 Study on Common API Framework for 3GPP Northbound APIs will consider their development, specifying common capabilities so that all Northbound APIs function similarly. The figure below, from draftTR 23.722, proposes how this may be achieved.
To realize standardized integration of services with diverse service providers, northbound APIs provide for interaction at the application layer. This makes it possible for mobile network operators to offer a wide range of services beyond prevalent teleservices - voice calls, SMS and data service. Those services can be exposed within the operator network or to third parties in other networks. The figure below is a simple model to illustrate how the Common Framework will develop as the study progresses. The blue lines are defined by for all services accessed by northbound APIs – a common framework. The red lines are specific interfaces to deliver a particular service.
3GPP has actively worked over the past decade to provide additional services in the area of 'machine type communication' (MTC) which delivers the mobile communications part of some important new sectors, including;
The 'Internet of Things',
Vehicle to Everything (including Vehicle to Vehicle, and other use cases)
These activities, particularly those related to Broadcast and IoT , have increased interest in standardization of northbound APIs. In Release 14, the "eMBMS Delivery of Media and TV Services" feature provide broadcasters with the ability to directly integrate their services with mobile network operators over standardized interfaces to the 3GPP system. In Release 15, to correspond with OneM2M release 2, 3GPP will include functionality to directly expose Cellular IoT and MTC capabilities via northbound APIs.
This expanding activity across 3GPP has provided the impetus for this new Study on Common API Framework (FS_CAPIF), which has begun to consider common aspects of northbound APIs. The study will focus on architectural aspects such as registration, discovery and identity management that generally apply to all services. Common API Framework Functions could be achieved uniformly for such capabilities as Service API discovery, monitoring and charging.
FS_CAPIF takes into account both the work ongoing within 3GPP as well as frameworks defined by other organizations. It aims to provide recommendations for specific architectural solutions that can subsequently be standardized. At this stage, requirements and issues have been identified and a gap analysis of existing solutions has begun.
While the scope of the study is general to all northbound APIs it is important to support the specific needs of individual vertical service offerings as well. For example, work on Broadcast interfaces has benefited from the participation of 3GPP member organizations actively providing broadcasting services. Similarly, MTC –related service exposure is coordinated directly with OneM2M and involves a wide range of other participants.
Looking to 5G
3GPP currently focusses significant resources on developing 5G standards. 5G aims to provide distinctive performance and capabilities to meet the needs of specific services. This will intensify the existing focus on integration with service providers in different service domains (often called 'vertical industries.') One aspect of this may be a broadening range of northbound APIs designed to expose the capabilities and resources of 3GPP operator's networks and the broad range of devices communicating over them.