As the title suggests, the focus of this chapter is on 4G and 5G radio access networks. 4G radio networks are designed to meet the requirements of ITU's IMT-Advanced framework. 3GPP's LTE-Advanced, which is an enhancement to LTE, is ITU's declared 4G technology. LTE-Advanced was standardized in 3GPP Release-10 in June 2011 and enhancements are continuously being made in each subsequent release. To distinguish the enhancements, 3GPP has identified Releases 8–9 as LTE, Releases 10–12 as LTE-Advanced, and Release 13 onwards as LTE-Advanced Pro. According to Global Mobile Suppliers Association (GSA), there are 194 LTE/LTE-Advanced mobile networks in 95 countries and out of these networks, 19 are LTE-Advanced Pro enabled in 15 countries. The count is increasing [1].