One of the main advantages of multiple antenna systems is the support of multi-user connections, simultaneously transmitting parallel data streams. This can significantly increase the overall system throughput. However, the spectral efficiency can be additionally increased through the usage of various dynamic strategies which take into account the current state of the system. Here we propose a method to evaluate the effectiveness of such strategies with the help of appropriate mathematical models. Purpose: Development of mathematical models for a multi-user MIMO system which would allow you to evaluate the average delay of a file transfer. Results: Mathematical models of the MIMO system are presented in the form of discrete/continuous time queuing systems for three user service strategies. We provide formulas for estimating the average file transfer delay in a closed form, which simplify numerical analysis as compared to the well-known methods using mathematical models in continuous time. This method allows you to find the most effective strategy with less computational complexity. Another advantage of the constructed models is the opportunity of further research on the effect of file length distributions on the file transfer delay. The conclusions we made about the effectiveness of each strategy are consistent with our earlier work, which is confirmed by a numerical example. Practical relevance: The developed mathematical models for a multi-user MIMO system can be used to set the operating parameters of a real wireless MIMO system.