Performance evaluation of macro-assisted small cell energy savings schemes

Abstract

Sleep mode techniques for small cells provide an effective means to mitigate excessive energy consumption and interference associated with ultra-dense small cell deployments. Nevertheless, such techniques can impact network performance in traditional deployments. In this paper, we show that in the particular case of macro-controlled small cells, such as in the Phantom Cell Concept (PCC) architecture, effective macro-assisted energy savings schemes can be employed to reduce the network energy consumption at practically no additional cost to the network and no hit to user quality of service (QoS). We introduce a heuristic algorithm suitable for real network operation, that minimizes the energy consumption in the small cell network by selecting the small cell offering the best signal-to-interference-plus- noise ratio (SINR). We apply this heuristic to three energy savings schemes realizable in the PCC architecture. These schemes,based on the macro-assisted user equipment (UE)-small cell connection establishment paradigm, are a downlink (DL) signalling based scheme, an uplink (UL) signalling based scheme and a database-aided scheme. We derive a power consumption model for a representative PCC small cell, which allows to quantify the percentage of energy consumed by a small cell in sleep mode with respect to a fully operational small cell for the three energy savings schemes considered. Furthermore, we characterize the connection latency associated with each scheme and evaluate the impact on system performance. System-level simulations show that, even with the associated connection delays, the macro-assisted energy-saving schemes can yield energy savings of more than 45 % while at the same time introduce throughput gains of up to 25 %.