  Sixth-generation (6G) networks are evolving towards new features and
order-of-magnitude enhancement of systematic performance metrics compared to
the current 5G. In particular, the 6G networks are expected to achieve extreme
connectivity performance with Tbps-scale data rate, Kbps/Hz-scale spectral
efficiency, and $\mu$s-scale latency. To this end, an original three-layer 6G
network architecture is designed to realise uniform full-spectrum cell-free
radio access and provide task-centric agile proximate support for diverse
applications. The designed architecture is featured by super edge node (SEN)
which integrates connectivity, computing, AI, data, etc. On this basis, a
technological framework of pervasive multi-level (PML) AI is established in the
centralised unit to enable task-centric near-real-time resource allocation and
network automation. We then introduce a radio access network (RAN) architecture
of full spectrum uniform cell-free networks, which is among the most attractive
RAN candidates for 6G TK$\mu$ extreme connectivity. A few most promising key
technologies, i.e., cell-free massive MIMO, photonics-assisted Terahertz
wireless access and spatiotemporal two-dimensional channel coding are further
discussed. A testbed is implemented and extensive trials are conducted to
evaluate innovative technologies and methodologies. The proposed 6G network
architecture and technological framework demonstrate exciting potentials for
full-service and full-scenario applications.
