Coexistence between radar and LTE-U systems: Survey on the 5 GHz band

LTE (Long Term Evolution) technology is unarguably becoming the primary standard for 4G cellular networks. But due to the tremendous growth in data traffic, LTE for Unlicensed Spectrum (LTE-U) has been proposed to allow cellular network operators to meet such high demands in data traffic. The initial studies for the choice of the unlicensed frequency bands for LTE-U suggested using the 5 GHz frequency band. The 5 GHz band is mainly occupied by different radar systems and by the 802.11 technology (Wi-Fi). There are different regulations imposed by the Federal Communication Commission (FCC) for each sub-band of the 5 GHz band to allow fair spectrum sharing. In this paper, we present a survey about the RF regulations and the different radar types within the different sub-bands of the 5 GHz band and we introduce the major approaches for spectrum sharing techniques.