Performance Analysis of NOMA Enabled User and Control Plane Split Architecture in 5G Systems

User and control plane split architecture is an effective solution to the frequent handover problem in ultra dense networks. Introducing non-orthogonal multiple access (NOMA) into such split architecture allows more flexible designs to further improve system performance. This work proposes a NOMA enabled user and control plane split architecture for two-tier heterogeneous cellular networks. In this system, a user equipment (UE) will select the base station (BS) providing the highest received signal power to receive data traffics, but always connects to its nearest macro base station (MBS) for control signal reception. Upon the application of NOMA, the control and data channels can be multiplexed on the same resource, which differs from traditional orthogonal multiple access (OMA) based systems. Under the stochastic geometry framework, the outage probability and outage rate are studied by jointly taking the signal-to-interference ratios of the data and control channels into account. Numerical results show that although NOMA based split architecture may impair the outage probability, it outperforms traditional OMA based architecture by bringing in a more flexible spectrum allocation and higher average user rates.