The evolution of mobile communication networks from 2G to 5G is briefly described. The assignment of scenarios for 5G mobile networks is noted. The architecture of the physical and data link layers of a 5G transport network is disclosed. The analysis of the requirements of the scenarios eMBB, URLLC, mMTC to the physical and data link layers of a transport network, their approximate numerical evaluation were carried out. The requirements that have a dominant influence in the construction of the network are identified, and their formalization is introduced. A mathematical model of requirements based on a matrix of weighting coefficients is proposed.