We perceive emerging developments in information and communication technologies (ICTs) in various areas of our dynamic live. The concept of getting services and applications 'any time' and 'any place' imposes the corresponding development in cellular networks. The rapid worldwide deployment of 4G LTE networks and increasing demand for new services are the key ICT trends that highlight the need for future improvements in technologies underling LTE. Although 3GPP concentrates all standardization activities in LTE, ITU-T recommendations reflect the main quality of service (QoS) requirements in ICTs. Nevertheless, not all QoS related ITU-T recommendations (i.e. E.800-E.899, G.1000-G.1999, Y.1500-Y.1599, Y.2100-Y.2199 series) correspond to today's variety of products and services provided by cellular networks. This fact raises the need for updates in these recommendations. In this paper, we explore QoS measures specific to LTE services adaptively occupying radio resources. This so-called pre-emption process assumes the service degradation as well as service interruption. We propose a pre-emption based radio admission control (RAC) model for two resource demanding video services - video conferencing and video on demand. We apply teletraffic and queuing theories to get a recursive algorithm for calculating its performance measures, namely, blocking probability, pre-emption probability, and mean bit rate © 2014 ITU.