In this paper, we study the QoE-based resource allocation problem for the downlink direction in LTE femtocells, considering the transport network limitation. The problem is first formulated as a convex optimization problem, which maximizes the aggregated QoE of all users and is then solved by Lagrangian relaxation method. This approach provides an optimal resource allocation solution but it is not practical, because the allocated bandwidth in the model is assumed to be a real value, while in practice, only an integer amount of Physical Resource Blocks (PRBs) can be assigned to a user. This integer constraint makes the problem non-convex and very hard to solve in real time. We therefore propose an efficient heuristic algorithm, which can be applied in LTE systems and take the optimal solution obtained from the Lagrangian method as the benchmark for our algorithm. The heuristic is mathematically proven to provide an optimal solution in case there is no limitation in the transport network. In case of transport network limitation, the simulation results show that it gives almost identical performance (ca. 1.5%) as the optimal solution in the investigated scenario.
