Energy efficiency gains of distributed antenna systems for non uniform user distributions

The demand for wireless applications with high data rates and strict quality of service (QoS) requirements continues to grow. This has placed huge obligations on wireless service providers to meet this need when rolling out radio access networks (RAN) in order to meet these capacity and coverage requirements. A distributed antenna system (DAS) is a RAN architecture that improves both coverage and capacity for both `dead-spots' and `hotspots'. In this paper, we investigate the energy efficiency gains of DAS in the case of non uniform user distributions. This investigation is conducted for outdoor hotspot scenarios and results show that the energy reduction gain (ERG) of DAS when Remote Radio Heads (RRHs) are located coincident with the hotspots improves with increasing numbers of users per hotspot as well as with increasing transmit power of the RRH. When RRHs are deployed coincident with hotspots, energy savings of 20% can be achieved. This is in contrast to the case when they are not, where losses of energy efficiency can be observed to result from the use of DAS.