Exploiting Coexistence Between UMTS and LTE for Greener Cellular Networks with Particle Swarm Optimization

Switching base stations (BSs) off is considered an effective method for improving energy efficiency. This switch-off approach is a system-level approach that can be applied to an area covered by multiple cells, even if those cells use different radio access technologies. This study focuses on exploiting the coexistence of universal mobile telecommunications system and long-term evolution to achieve a balance between network performance (meeting the demands for high data rates at peak traffic hours) and energy efficiency based on traffic load variations while guaranteeing maximum coverage for the region. Particle swarm optimization has been adopted to maximize the cells’ coverage area during a switch-off session with constraints for the transmission power of the BS (P _tx ), the total antenna gain (G), the signal-to-interference-plus-noise ratio, and shadow fading (σ). Moreover, the modulation and coding scheme and data rate are considered in this study. The results show that daily energy savings of up to 27.86 % can be achieved while guaranteeing cell coverage.