The vision of the OpenRAN architecture is to design radio access network architecture with the following characteristics: Flexible,Distributed,Scalable.
Such architecture would be open because it defines open, standardized interfaces at key points that in past architectures were closed and proprietary. It would be flexible because it admits of several implementations, depending on the wired network resources available in the deployment situation. It would be distributed because monolithic network elements in architectures would have been broken down into their respective functional entities, and the functional entities would have been grouped into network elements that can be realized as a distributed system. The architecture would define an interface with the core network that allows the core network to be designed independently from the RAN, preserving access network independence in the core. Finally, the architecture would not require changes in radio link protocols; in particular, a radio link protocol based on IP would not be necessary. This document presents the first steps in developing the OpenRAN vision. In its first phase, the subject of this document, the OpenRAN architecture is purely concerned with distributing RAN functions to facilitate achieving open interfaces and flexible deployment. The transport substrate for implementing the architecture is assumed to be IP but no attempts is made to optimize the use of IP protocols, nor are specific interfaces designated as open. The architecture could as well be implemented on top of existing functional architectures that maintain a strict isolation between the transport layer and radio network layer, by splitting an existing radio network layer into control and bearer parts. In addition, interoperation with existing core and RAN networks is supported via interworking functions. Chapters 7 through 11 in this report are exclusively concerned with this first phase of the architecture, and it is possible that the architecture may change as the actual implementation of the OpenRAN is considered and For Further Study items are resolved.