Energy efficient radio resource management in a coordinated multi-cell distributed antenna system

As well as the demand for higher data rates goes on, the rising energy costs and environmental concerns have also led researchers to increase energy efficiency in terms of bits-per-Joule. Cooperative communications with low power nodes, switching off under-utilized cells due to low traffic load and energy efficient radio resource management are some of the energy saving methods. It is observed that the conventional energy efficiency expression, which is defined as the ratio of the data rate to the total transmission power, can limit the system throughput significantly. In this paper, we introduce a novel energy efficiency expression which provides a trade-off between sum-rate maximization and total transmission power minimization in the network. A coordinated multi-cell distributed antenna system is considered and two energy efficient radio resource management schemes are investigated; either ports can be switched on and off or their transmission power can be adjusted in order to maximize energy efficiency. It is demonstrated that the proposed expression offers significant increase in data rate while keeping total transmission power low. The proposed and the traditional energy efficiency methods asymptotically converge when tradeoff effect diminishes, i.e., transmission power minimization takes the full priority.