  The 5th Generation cellular network may have the key feature of smaller cell
size and denser resource employment, resulted from diminishing resource and
increasing communication demands. However, small cell may result in high
interference between cells. Moreover, the random geographic patterns of small
cell networks make them hard to analyze, at least excluding schemes in the
well-accepted hexagonal grid model. In this paper, a new model---the matrix
graph is proposed which takes advantage of the small cell size and high
inter-cell interference to reduce computation complexity. This model can
simulate real world networks accurately and offers convenience in frequency
allocation problems which are usually NP-complete. An algorithm dealing with
this model is also given, which asymptotically achieves the theoretical limit
of frequency allocation, and has a complexity which decreases with cell size
and grows linearly with the network size. This new model is specifically
proposed to characterize the next-generation cellular networks.
