Energy efficient PRACH detector algorithm in SDR for LTE femtocells

Mobile telecommunication networks are increasingly contributing to global energy consumption with the largest amount of energy consumed at the base station (BS) and at the core network side. Currently, large (macro) base stations can satisfy the user requirements; however the trend of deploying heterogeneous networks with both large and small base stations will be required to cover the user throughput demands. This will increase the already large contribution of mobile networks to global energy consumption. Traditionally, energy efficiency (EE) techniques have been proposed at the BS to reduce the energy consumption during downlink (DL) data transmission and idle periods. Nevertheless, during uplink transmissions, the random access procedure plays an important role for energy consumption since it has be to executed continuously, also when little data is being transmitted in the cell. The objective of this paper is to explore the energy consumption of the random access detector and to evaluate some techniques to improve its EE in a software defined radio (SDR). We show that through the use of a single antenna chain, and the generation of the random access preambles from one root sequence, we can decrease the energy consumption depending on the SNR at the detector by 82% without degrading the probability of detecting all the users. Part of this work is done for the Energy Aware Radio and network technologies (EARTH) project.