  In recent years, the radio access network (RAN) domain has witnessed a sea
change with increasing levels of virtualization and softwarization driven by
emerging paradigms such as the Open RAN (O-RAN) movement. However, the
fundamental building block of the cellular network, i.e., the base station,
remains unchanged and ill-equipped to handle this architectural evolution. In
particular, with reference to existing base station architectures, there exists
a general lack of programmability and composability along with a protocol stack
that grapples with diverging and often conflicting requirements set forth by
3GPP and O-RAN. Recognizing the need for an "O-RAN-native" approach to base
station design, this paper introduces HexRAN- a novel base station architecture
characterized by key features relating to RAN disaggregation and composability,
3GPP and O-RAN protocol integration and programmability, robust controller
interactions, and customizable RAN slicing. Furthermore, the paper also
includes a concrete systems-level prototype and comprehensive experimental
evaluation of HexRAN on an over-the-air testbed, showcasing the scalability and
performance benefits associated with the proposed architecture.
