This chapter presents the global concepts of 4G-LTE and 5G-NR cellular networks, including main difference between these two communication technologies, primarily in terms of frequency spectra and network structures. 4G-LTE uses the spectrum up to 6 GHz, while 5G uses the spectrum up to 50 GHz and beyond, which leads 5G network to much greater capacity (rate) than 4G network. Regarding network structure, 4G-LTE uses RF links, or radio access network (RAN) layer, between base stations, whereas 5G-NR uses both RAN layer and internet (cloud) layer for connecting users in the same and other 5G networks. Additionally, the cases of 5G network applications are considered in this chapter, such as Massive Machine Type Communications (m-MTC), Enhanced Mobile Broadband (e-MBB) Services, and Ultrareliable and low latency communications (URLLC). Additionally, from the EMI stand point, the use of massive MIMO, i.e., Spatial Division Multiplexing (SDM), is considered in this chapter. Additionally, concerning EMI, optimal 4G and 5G network cell and EMI shielding of network equipment and devices are considered in this chapter.