Introduction.Because of the fast technological development, cellular connection networks are becoming such type of the network domain that could support several frequency ranges of different cellular generations and it needs to have an optimal antenna design structure to have the most efficient signal receiving. So the multiple input multiple output (MIMO) antennas were chosen as the most appropriate instrument to operate at 5G mobile networks. According to purpose, all 5G cellular connection antenna systems could be relatively divided into two types: base station antenna systems and antennas for mobile apps. In one's turn, dependently from the frequency range, each of defined types include two subgroups, such as: lower than 6 GHz and higher than 6 GHz. 5G base station MIMO antenna systems for the range that is lower than 6 GHz are often integrating to the 4G antenna systems that simplifies its accomplishment and its placing on the cell tower.Purpose of the paper is to discover good decoupling and carrying capacity securing in moderate dimensions of the antenna elements during the antenna designing for the 5G mobile apps. 5G system architecture depends on universal antenna design for the millimeter range tasks solving. One of such tasks is large losses overcome on the way of millimeter wave spreading at the free space that weaken signal power significantly.Results of the research is in definition of the most efficient decoupling and carrying capacity support of the MIMO antenna system. Total dimensions, compact location and optimal work parameters are also reasons for the best MIMO antenna system design definition for its usage for the 5G wireless network mobile applications.Conclusion. The most optimal structure design for MIMO antenna system could be a real step forward at cellular technologies. Using advantages of all previous network generations, the brand new MIMO wireless antenna system has abilities to work with minimal losses and in the most flexible and frequency-optimal way ever. Development also demonstrates influence of the dimensions on the base station block location and universality of its usage complexly with antennas of, practically, any possible design.