In this paper, we propose a resource block allocation scheme for LTE systems (Long Term Evolution) in order to attain QoS requirements based on the effective bandwidth theory. To this end, first we propose an adaptive algorithm to estimate the Multifractal Wavelet Model (MWM) parameters in order to calculate the effective bandwidth for the incoming traffic flows into the system. Next, we apply a PSO (Particle Swarm Optimization) algorithm in order to decide the number of resource blocks to be allocated to each user, providing a minimum rate per user. We validate the efficiency of the proposed adaptive allocation scheme via simulations with real traffic traces.