This paper provides a theoretical analysis of the latest results in the field of non-perfect time-synchronization for Filter Bank Multi Carrier (FBMC) systems using an Offset Quadrature Amplitude Modulation (FBMC/OQAM). In our work, we analyze the interference caused by timing offsets for the FBMC/OQAM transmission model. A part of our study, is to simplify the resulting equations in order to provide a clear view on the impact of timing offset on the system performance. We derive the interference power in a very simple
expression containing both inter-symbol interference (ISI) and inter-carrier interference (ICI), with which an exact signal to interference ratio (SIR) expression is presented. The numerical
simulations are further carried out using different prototype filters for FBMC/OQAM to confirm the correctness of our analysis. In the case of an orthogonal prototype filter, we show that we exactly recover a previously published result that, up to now, has been unnoticed.