In this paper we report on simulations of LHCD in JET closely comparing the simulation results to the available experimental data. The simulations are performed all over the relevant discharge duration by ASTRA. The LHCD module, FRTC, is based on a standard Ray tracing Fokker Planck model. The main purpose of the paper is to understand the present LHCD experiments issues within the limit of the LH linear propagation model. Such main issues are: i) analysis of Non Resonant Collisional Absorption (NRCA) of LH wave power at JET during the current ramp up phase and in steady state scenarios, ii) the associated problem of lack of penetration of LHCD in high density plasmas, iii) current diffusion during the LHCD assisted current ramp up and iv) assessment of the current profile alignment in JET Steady State (SS) discharges in the presence of LHCD. In recent experiments from many machines (FTU, JET, C_MOD) LHCD effects at high plasma density are either completely absent or less than expected. It has been shown, both in FTU and C_MOD, that NRCA of LH wave power can be responsible for that. Indeed NRCA is estimated to be small in JET plasmas, at least in the main heating phase and therefore it is not responsible for the lack of penetration of LHW in high density JET plasmas, however here we show for the first time that it can be effective during the early phase of the current ramp up, when the plasma is still collisional. On the contrary it is suggested that the reduction of LHCD effects at high density may be attributed at least partially to the loss of accessibility of the n|| spectrum effectively launched into the plasma. Current diffusion during the current ramp up has already been analyzed in JET but mainly in discharges without LHCD. Here the current diffusion during the LHCD assisted current ramp up is investigated and a careful comparison between the simulated q profiles and the measured ones is performed over time. The implications of the observed difference are discussed. Finally the important question of the alignment of all the current profile components is analyzed in JET SS discharges at high bN, providing useful information if the steady state is achieved in these shots and how far the plasma is from SS.