This article presents a model for assessment of reliability of data transmission via wireless network. The developed model considers topology of the network evaluates telecommunication equipment and allows to select optimal paths of communication considering attenuation of the signal inside the building. The model of reliability stated in the article considers systems capable of being in two characteristic states: a state of full implementation of the purpose, or a state of total functioning failure. The work describes a problem of distribution of radio waves inside buildings taking into account existence of walls and partitions. These obstacles create a difficult environment for distribution of radio waves via Wi-Fi network, which significantly differs from the distribution of radio waves in free space. Results of signal measurements are obtained with the frequency of 5 GHz (Wi-Fi) on attenuations in the building at different distances from the transmitter. This reliability assessment model is universal and can be applied at solving problems related to the development of wireless sensor networks, for example, the analysis of network’s throughput capacity, optimization of topology, determination of optimal mode of its operation and service.