Efficient uplink resource allocation for power saving in IEEE 802.16 OFDMA systems

In this paper, we define a resource allocation problem focusing on the scheme minimizing energy consumption of subscribers in uplink subframe of the IEEE 802.16 OFDMA systems. In order to clearly formulate the relation between the uplink resource allocation and energy efficiency of subscribers, we use the Multiple Choice Knapsack (MCK) problem, which is proved to be an NP-hard problem. Instead of finding an optimal solution, we seek a suboptimal solution. Based on the problem formulation, we adopt the existing solution of the Multiple Choice Knapsack problem to solve the resource allocation problem. The suboptimal solution adaptively uses the modulation and coding scheme defined in the IEEE 802.16 systems to minimize the required transmission power while guaranteeing QoS. Our simulation results show that the suboptimal algorithm can reduce the energy consumption up to 53% compared to the channel state information (CSI) scheme, which determines the modulation and coding level only considering the channel state information.