Algorithm 1: Improved GMM User Clustering Algorithm

$1: \mathrm{Input} \mathrm{user} \mathrm{coordinates} \mathrm{and} \mathrm{base} \mathrm{station} \mathrm{location}, \mathrm{then} \mathrm{compute} \mathrm{the} \mathrm{initial} \mathrm{values} \mathrm{for} \mathrm{the} \mathrm{number} \mathrm{of} \mathrm{clusters} M$ and means $\mu$. $2: \mathrm{Initialize} \mathrm{parameters} {\prod }_m$$\mathrm{and} {\coprod }_m$. 3:  Repeat $4: \mathrm{E}\text{-}\mathrm{Step}: \mathrm{Keep} \mathrm{parameters} {\prod }_m,{\coprod }_m,{\mu }_m$$\mathrm{unchanged}. \mathrm{Compute} \mathrm{the} \mathrm{posterior} \mathrm{probability} \mathcal{l}(z_i^m)$$\mathrm{of} \mathrm{user} u_i$ by (10). $5: \mathrm{M}\text{-}\mathrm{Step}: \mathrm{Keep} \mathcal{l}(z_i^m)$$\mathrm{unchanged}. \mathrm{Update} \mathrm{parameters} {\mu }_m,{\coprod }_m,{\prod }_m$ by (12), (13), and (14). $6: \mathrm{Repeat} \mathbf{until} \mathrm{the} \mathrm{objective} \mathrm{likelihood} \mathrm{function} L^{\prime }$ converges or the maximum number of iterations is reached.