Optimal Delayed Wi-Fi Offloading

Wi-Fi offloading can help the mobile operator to obtain immediate capacity relief when facing the explosive growth of mobile data traffic. In this paper, we study the Wi-Fi offloading problem with delay tolerant applications. We formulate it as a finite-horizon sequential decision problem, where the objective is to minimize the total cellular usage plus the potential penalty for deadline violation. We solve the problem optimally using dynamic programming, and propose a general optimal delayed Wi-Fi offloading (ODWO) algorithm. For the special case with a convex penalty function and fixed location-independent data rates, we show that the optimal policy exhibits a threshold structure. A monotone ODWO algorithm with a lower complexity can be used in this case. Simulation results show that the ODWO scheme achieves both the minimal total cost and the highest file transfer efficiency as compared with two heuristic schemes.