Energy Efficiency by Cell Reconfiguration: MIMO to Non-MIMO and 3-Cell Sites to Omni

Altering the network configuration in order to reduce the energy consumption in a WCDMA network is under study in this paper. The baseline configuration is a MIMO enabled network with 3-cell sites. In case there are no MIMO users in a cell, one of the MIMO antennas and the corresponding power amplifier in this cell is turned off. Furthermore, if the user distribution is such that the traffic can be handled by an Omni configuration, the site is re-configured to an Omni site. The transmission powers for the different configurations are assessed through system simulations and fed into a base station energy consumption model, based on the predicted network configuration assuming different loads of fixed bit rate users. It is found that in a low load scenario, the energy savings can be up to 15-25 percent simply by turning off one of the MIMO antennas when the fraction of MIMO enabled users is 25-75 percent. If reconfiguring to Omni cell as well as turning off one MIMO antenna when permitted, the savings can be up to 40 to 50 percent with the same fraction of MIMO users in a low load situation. Savings by reconfiguration to Omni cells when there are no MIMO users in the system gives saving of up to 28 percent in a low load scenario. It is concluded that the proposed techniques has the potential to yield substantial energy savings in low load scenarios without degrading the user performance.