In a cellular radio access network (RAN) relying on control-and user-plane separation, control base stations (CBSs) form the control plane (CP) and take care of control coverage as well as low speed data delivery. In contrast, traffic base stations (TBSs) in the user plane (UP) are used for transmitting high speed data. Based on queuing theory and stochastic geometry, we derive the coverage probability of the CP under non-line-ofsight (NLoS) transmissions, and derive the energy efficiency of the UP under coexisting line-of-sight (LoS) and NLoS propagation modes. Numerical results show that when the traffic load is high, the coverage probability of the CP increases with the increasing CBSs' data rate or the density of CBSs. We also found that the maximum energy efficiency of the UP can be achieved by optimizing the TBS density, while achieving a high area spectral efficiency.

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