Algorithm 2: Pilot Allocation to Central and Edge Users

Step 1: Randomly select F neighboring cells from the system, and record the target cell as $\mathrm{s}$, the number of cell users is $\mathrm{K}$, and the pilot number is recorded as $\mathsf{\zeta }$, and the large-scale fading factor is determined from the user to the BS.

Step 2: Choose the appropriate parameter $\mathsf{\lambda }$, calculate the grouping threshold using equation (28), and record ${\mathrm{K}}_{\mathrm{c}}=0,{\mathrm{K}}_{\mathrm{e}}=0$.

Step 3: Check the cell users one by one and compare it with the threshold. If the user is greater than the given threshold, then ${\mathrm{K}}_{\mathrm{c}}={\mathrm{K}}_{\mathrm{c}}+1,$ otherwise ${\mathrm{K}}_{\mathrm{e}}={\mathrm{K}}_{\mathrm{e}}+1$.

Step 4: Number of all orthogonal pilots are ${\mathsf{\Omega }}_{1,}{\mathsf{\Omega }}_{2,},\dots ,{\mathsf{\Omega }}_{\mathsf{\zeta },}$. First, the central users are assigned the value from ${\mathsf{\Omega }}_1$ to ${\mathsf{\Omega }}_{{\mathrm{k}}_{\mathrm{c}}},$ then assign pilots to the remaining ${\mathrm{K}}_{\mathrm{e}}$ users. For ${\mathrm{K}}_{\mathrm{c}}$ users in other cells assign the same value from ${\mathsf{\Omega }}_1$ to ${\mathsf{\Omega }}_{{\mathrm{k}}_{\mathrm{c}}}$, and the edge user continues to allocate orthogonal pilots.

Step 5: Other cells of the system can be allocated following the above steps.