Evolution of RAN-Core Convergence Toward 6G: An Analysis of the Key Technologies, Principles, and Challenges

The adoption of cloud nativeness in the form of Service-Based Architecture (SBA) have played a significant role in shaping 5G networks. Despite these design architecture principles, the Radio Access Network (RAN) and Core Network (CN) were developed separately following different paradigms and thereby limiting the provision of end-to-end SBA in the Fifth Generation (5G) CN. Such logical separation accelerates the deployment of RAN and CN but at the same time it brings limitations in terms of duplicate functionalities, signaling overhead and complexity, since there is a need for coordination for enabling end-to-end processes, e.g., Quality of Service (QoS) provision. As the emerging use cases for the forthcoming Sixth Generation (6G) era rely on a tight cooperation of RAN and CN new innovative solutions are essential. This article highlights the main challenges behind RAN-CN convergence and derive the main principles behind RAN-CN convergence shedding light into different deployment options.