The concept of getting services and applications at “any time” and at “any place” requires the corresponding development of cellular networks, namely in LTE networks. At present, there is a lack of quality of service related recommendations describing various popular services, e.g., video conferencing. The problem is to find the optimal bit rate values for this service while not affecting the background lower priority services. In this paper we propose an instrument for solving this problem. First, we obtain mathematical model in the form of a queueing system with multicast highpriority traffic and unicast background traffic. The admission control assumes the adaptive bit rate change of multicast traffic and unicast traffic interruption. Second, we obtain the recursive algorithm for calculating mean bit rate and other performance measures. Third, we study the problem of optimizing mean bit rate. © 2016 Springer Science+Business Media New York