Uplink resource allocation for interworking of WLAN and OFDMA-based femtocell systems

Efficiency of the wireless local area network (WLAN)/femtocell interworking system essentially relies on the efficiency of the resource allocation protocol employed in the system. Efficiency of the resource allocation protocol depends on whether it has been designed considering physical layer and medium access control layer technologies of different networks in the interworking system. Therefore, in this paper, we formulate a resource (user, subcarrier, and power) allocation problem for maximizing the sum of weighted rates of the interworking system considering multi-homing capable users and the main features of IEEE 802.11 distributed coordination function (DCF) and orthogonal frequency division multiple access (OFDMA) based femtocell networks. Solving this problem optimally is prohibitively complex as it is a non-convex problem. Thus, the problem is sub-optimally solved by dividing it to two sub-problems. A heuristic algorithm is proposed for user and subcarrier allocation while an optimal and fast converging power allocation algorithm is derived based on dual decomposition and the characteristics of Lagrangian. Simulation results have shown that the proposed resource allocation protocol achieves results close to the optimum.