Two levels water-filling scheme for energy saving in LTE system

Energy saving plays a significant role in the communication system. Moreover the traffics of 3GPP are expanding and getting ever more complex. We can save more energy by taking advantage of the fact that different traffics have different QoS requirements. This paper proposes a model for such kind of optimization problems. However, it is difficult to find the optimal solution. So in the view of engineering, we propose a scheme, Two Levels Water-Filling Scheme (TLWFS), to improve the energy efficiency while guaranteeing the QoS requirements. In TLWFS, firstly, we classify the traffics into two categories, which are Rate Constrained Traffic (RCT) and Rate Non-Constrained traffic (RNCT). Secondly, at the first water-filling level, the high SNR Resource Blocks (RBs) are selected to guarantee the RCT, with traditional water-filling algorithm. Finally, at the second water-filling level, the energy and RBs left are used to transfer the RNCT, with directional water-filling algorithm. Numerical results indicate that the TLWFS works well in LTE system, with the energy consumption decreased by 10% with TLWFS, compared to traditional power allocation scheme.