The Open Radio Access Networks (RAN) industry is dynamically evolving, transitioning from closed, monolithic architectures to open architectures that are based on the decomposition of physical and virtual functions, supporting interoperable interfaces that enable multi-vendor deployments. While encouraging competition among vendors, open RAN simultaneously drives supply chain diversification. This same broadening of the RAN ecosystem opens up innovation opportunities. Simultaneously, Open RAN delivers both a simplified network management, that is now standardized across multiple vendors, as well as being highly scalable through the use of cloud-native operations. Finally, Open RAN facilitates data accessibility, enabling AI/ML based analysis and optimizations.
Importantly, as interoperability standards and testing mature, forecasts predict that Open RAN deployments will gain momentum after 2025, ultimately leading to an estimated 1.3 million Open RAN cell sites by the end of the decade. This momentum can only be achieved through Open RAN transitioning from early deployments that have focused on greenfield deployments into a technology that is widely adopted in brownfield deployments across all mobile network operator segments and geographies.
This technical paper, building on the groundwork laid by previous 5G Americas Open RAN publications, offers updates on the progress made by leading Open RAN standards bodies, the latest advancements in multi-vendor interoperability, and current market deployments. From a standardization standpoint, the technical paper delves into recent developments in Open RAN architecture, security, and architectural elements such as the RAN Intelligent Controllers (RICs).
In this paper, we focus on the recent updates to the O-RAN architecture, including decomposition of the SMO with individual SMO functions integrated within a SBA. The R1 interface has been introduced, which allows the Non-RT RIC to expose information to consuming rApps that perform RAN optimization. From a Near-RT RIC perspective, the role of xApp APIs has been described, enabling xApps to be fully decoupled from the Near-RT RIC platform. Finally, new UE ID capability is described, allowing correlation of events by xApps and rApps and RAN optimizations to be performed on a per-UE basis.
Other recent specification updates are detailed, including use-case updates to improve the performance of Multi-User and Massive MIMO deployments. With spectrum efficiency being a key performance indicator for the RAN, the latest O-RAN specifications have defined new MIMO features for grid-of-beams and non-grid-of-beams optimizations. Advancements in radio resource management are introduced, including introduction of the RAN-Specific Network Slice Subnet Management Function that enables slicing SLA use cases to be realized. O-RAN’s shared O-RU capability is introduced, enabling a neutral host to partition the shared O-RU’s carrier resources between separate MNO tenants, with each MNO operating carriers using their own dedicated spectrum, and role-based access control permitting those MNO tenants to only configure and receive performance data from their own partitioned resources.
We have also covered advances related to the O-RAN security and architecture. Building on earlier papers that have introduced the activities of O-RAN Working Group 11, updates are provided concerning O-RAN threat modeling, analysis and remediation. Furthermore, updates to the security protocols are described, including mandatory use support of IEEE 802.1X port-based network access control to protect the Open Fronthaul interfaces. ZTA principles related to O-RAN are also detailed. Whereas the RAN was previously considered as a trusted environment, O-RAN is leading the introduction of ZTA into the RAN, ensuring that there is no implicit trust of a RAN service producer, consumer or RAN asset based upon physical location, network location, or ownership.
The paper describes updates to the RIC and SMO domains. Architectural updates to the RIC are introduced, including the publication of Near-RT-RIC APIs, enabling 3rd party xApps to be hosted on different Near-RT RIC platforms. From an interface perspective, the Y1 interface is described, enabling service to easily consume RAN analytics, as well as the R1 interface that enables rApps to be decoupled from the Non-RT RIC platform functionality. Finally, updates are described that focus on the testing of the multi-vendor interoperable RIC architecture. O-RAN test specifications for the E2 interface are described, including conformance testing requirements to ensure full multi-vendor interoperability between E2 nodes (O-CU CP, O-CU UP, O-DU, O-eNB) and the Near-RT RIC platform.
Continuing the theme of multi-vendor interoperability, the paper reports on the recently announced O-RAN Certification and Badging Program, describing the differences between O-RAN defined certification, IoT badging and E2E badging. Current O-RAN testing programs are described as well as reports of products that have completed Open Fronthaul certification. Complementing O-RANs Certification and Badging, the paper describes TIP’s Open RAN System Certification Process and how this is focused on testing of complete RAN systems that may include non-O-RAN components, as well as certification of system integration aspects such as Open RAN configuration and optimization.
Recognizing that Open RAN is the fastest growing segment in the RAN market, but also its smallest, the paper describes progress in both greenfield and brownfield deployments. As interoperability standards and testing mature, operator sentiment is recited, indicating forecasts of large-scale deployments from 2025. This aligns with industry analysis that is forecasting Open RAN deployments gaining momentum after 2025, ultimately leading to an estimated 1.3 million Open RAN cell sites by the end of the decade.
Finally, the foundation of this technical paper is represented by specifications published by O-RAN ALLIANCE in June 2023. However, 5G Americas recognizes that there is significant interest in more recent specification developments which are still work in progress. These topics are covered in the appendix and highlight the continued innovation that is occurring across the Open RAN industry.