Energy saving using traffic adaptive base station operation (cell DTX) in heterogeneous cellular networks

Abstract: Nowadays, mobile broadband data traffic is growing exponentially and will continue to grow for the coming years. Accordingly, the operational cost of a mobile network will increase significantly due to the fact that a large number of base stations will be deployed to support the high traffic demand. Besides, the increase of the power consumption of a mobile network has a negative impact on the environment because of increased carbon footprint. As a result, energy efficiency in cellular networks has gained a great interest in the research community. Hence, several approaches have been investigated to lower the mismatch between base station operations and temporal and spatial characteristic of the traffic demand in a network. For example, cell discontinuous transmission which deactivates some portion of the BS during the unused transmission time interval (TTI) is one of the techniques proposed to reduce power consumption in LTE networks. This thesis work investigates potential energy savings due to the deployment of low power BSs that have cell DTX capability in a cellular mobile radio network in both urban and dense urban area deployments. A time static system level simulation has been used in a downlink communication in order to evaluate and demonstrate the energy savings. Besides, the European long term large scale traffic model has been implemented to make the system level simulation more realistic. Areapower consumption is used as the main performance metric to evaluate the energy saving in the deployment options and traffic adaptive energy efficiency features considered. Results show that, the power saving of a hetrogenous network increases as a result of the enhancement of the BSs’ hardware to put itself in to sleep mode and by deploying an optimum number of low power BS at the cell border of the macro BS considering hotspots. However, the energy efficiency techniques that can be implemented to give maximum power saving highly depends on the traffic demand of the deployment area. Hence, there is no benefit of deploying small cells if the demand is low and if there is no significant traffic load to offload from the macro layer. In this work, using the traffic model mentioned above and time static system level simulation, it is found that an optimal number of small cells per macro gives the minimum area power consumption when the BS is capable of switching off 90% of its components during idle mode in a dense urban area deployment. This deployment scenario has around 36% power saving during the peak hour and 12.5 % daily average power saving compared to a macro only network with cell DTX capability. On the other hand, under urban area traffic scenario, heterogeneous deployment for the same cell DTX factor does not bring any area power consumption reduction.