Energy-aware resource allocation in OFDMA wireless multicasting networks

In this work, we address the problem of energy-aware multicasting in OFDMA wireless networks. We investigate the optimal allocation of resources with bit rate adaptation to multicast a common content to a set of requesting mobile terminals. In the case of multicasting, the bit rate is limited by the worst channel condition among the receiving mobile terminals on the same subcarrier. In this work, we assume a set of subcarriers is available for multicasting. We aim at dividing the mobile terminals into groups based on their channel conditions such that each group receives on one of the carriers. This is expected to lead to performance gains since the mobile terminals with good channel conditions will not sacrifice and consume an extra energy to receive with a low bit rate due to the existence of mobile terminals with bad channel conditions in the network. First, we formulate the multicasting resource allocation problem as a linear mixed integer programming problem that minimizes the total energy consumption of the mobile terminals. Since the problem is NP-hard, we propose a polynomial time heuristic algorithm to solve it when the optimal solution becomes computationally complex as the network size increases. Simulation results demonstrate significant energy consumption savings compared to traditional multicasting schemes. Moreover, the proposed heuristic algorithm is shown to have a close-to-optimal performance.