The impact of the Radio Frequency heating and current drive systems on JET advanced scenarios at high density is analyzed by means of the CRONOS suite of codes for integrated tokamak modelling. In particular, the performance of the proposed Electron Cyclotron heating and current drive system for JET is evaluated. As a first step, the code is applied in the interpretative mode to analyze two high power advanced scenario discharges of JET, in order to validate both the heating and current drive computational modules and the overall simulation procedure. Then, JET advanced scenarios are studied by predictive simulations on the basis of previous results. The simulations show that Lower Hybrid and Electron Cyclotron heating and current drive systems can provide together off-axis current in order to create and sustain steady-state scenarios on JET at high density. These results give deeper insight into the future advanced scenarios in ITER.