Assessment of Alternatives for Reducing Energy Consumption in Multi-RAT Scenarios

Modern radio base stations (RBSs) typically consist of components such as radio units (RUs) and digital units (DUs) that are capable of supporting multiple radio access technologies (RATs) at the same time. This enables several different possible configurations of a multi-RAT site and in this paper we assess the energy performance of some promising configurations. We start by evaluating an LTE-only network and conclude that with traffic according to predictions for 2015 the average cell will be idle 95% of the time and the additional energy consumption due to the user plane traffic is only 1.4%. We also show that even a significant future traffic increase will only have a minor impact on the energy consumption. We further show in this paper that a multi-RAT RBS where the RATs share the digital unit (PA) have the potential to reduce the site energy consumption with 40% compared to a multi-RAT RBS with separate PAs for each RAT. For operators with multiple RATs on the same site but using separate PAs per RAT, it is still possible to reduce energy consumption by utilizing load balancing between the RATs. This study shows that a potential energy reduction in the order of 30% is possible by utilizing load balancing between HS and LTE.