The paper considers the suboptimal version of GNSS integrity monitoring algorithm involving multichannel signal processing. This algorithm was examined in terms of probability-based cha-racteristics obtained during semi-natural modeling. Such modeling assumes that multichannel snapshots are getting from real channels of multichannel GNSS receiver including antenna array when all subsequent procedures are implemented in Matlab later. Probability-based characteristics obtained in such way consequently checked with similar characteristics obtained by Matlab simulation ideal model, which ignored probable effects of signal transmission and reception in real environment. It was shown the level of similarity between characteristics of both types, and also clarified the conditions when the characteristics are close to each other, and the conditions when the difference between them is significant. The main reason of such difference was found out empirically.