Nowadays, mobile cellular networks are based on the well-known hexagonal mesh in which nodes are considered as base stations. However, this model does not really take into account the irregularity and the randomness of central offices locations in a large telephone network. As we cannot transform this telephone network into a regular structure, because of spatial variations of population density, consumer demand, other geographical and technological factors, Voronoï cellular networks appears to be the more suitable model. In this paper, we describe the Voronoï cellular model and its topological properties.