The received uplink signal \begin{equation} y_{ij} = \underbrace{\mathbf{u}_{ij}^H \mathbf{h}_{ij} \sqrt{p_j} x_j }_{\text{Signal Component}} + \overbrace{ \sum_{k\neq j, k=1}^N \mathbf{u}_{ij}^H \mathbf{h}_{ik} \sqrt{p_k} x_k}^{\text{Multiuser Interference (MUI)}} + \underbrace{n_i}_{\text{AWGN Component}} \end{equation} $$\\$$ $h_{ij}$ is the complex channel between UE$_j$ and BS$_i$. For the assumed small scale fading, each component i.e., the real and imaginary parts has a mean=0 and variance=0.5. $$\\$$ Both the intra-cell and inter-cell UEs contribute to the MUI. $$\\$$ $u_{ij}$ is the receive beamforming vector at BS$_i$ for UE$_j$ and $\| u_{ij} \|_2=1 $.