channel is constant, i.e., $T=196$. The cell radius is $R_{\max}=250$ m and the minimum distance is $R_{\min}=35$ m. The pathloss exponent is $\alpha=3.76$ and the reference LSF factor is $c=10^{-3.53}$. The total noise power is assumed as $\sigma_{\text{n}}^2=-96$ dBm.

Sum Rate Performance\[sub:Sum-Rate-Performance\]
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![Sum rates of $K$-RUS and $K$-LUS. $P=30\text{ dBm},M=32,N=64.$[]{data-label="fig3"}](sim1){width="7.5cm"}

![Contour figures of $K^*_{\text{RUS}}$, $K^*_{\text{LUS}}$, $R^*_{\text{RUS}}$ and $R^*_{\text{LUS}}$ against $P\text{ and }N$. $\rho=0,\delta=0,M=32.$ $K^*_{\text{RUS}}$ and $K^*_{\text{LUS}}$ are shown in (a) (i.e., the top-left sub figure) and (b) (i.e., the top-right sub figure) with solid lines, respectively. $R^*_{\text{RUS}}$ and $R^*_{\text{LUS}}$ are shown in (c) (i.e., the bottom-left sub figure) and (d) (i.e., the bottom-right sub figure) with dash lines, respectively. []{data-label="fig4"}](sim2){width="7.5cm"}

![Contour figures of $K^*_{\text{RUS}},K^*_{\text{LUS}},R^*_{\text{RUS}}$ and $R^*_{\text{LUS}}$ against $\rho\text{ and }\delta$. $P=30\text{ dBm},M=32,N=64.$ $K^*_{\text{RUS}}$ and $K^*_{\text{LUS}}$ are shown in (a) and (b) with solid lines, respectively. $R^*_{\text{RUS}}$ and $R^*_{\text{LUS}}$ are shown in (c) and (d) with dash lines, respectively. []{data-label="fig4-1"}](sim3){width="7.5cm"}

In Fig. \[fig3\], the sum rate performance of $K$-RUS and $K$-LUS as a function of $K$ is evaluated in the case of $P=30$ dBm, $M=32$ and $N=64$. The simulated ergodic sum rates (marked as ’Sim.’ in the figure) are obtained by averaging over 10000 independent channel realizations (both SSF and 