lity of experience. Backhaul is the confluence of mobile broadband users, small cells, DAS, macro-cells, and the core network. The emerging HetNet topologies have created a need for diverse wired and wireless mobile backhaul solutions. Small cells are being deployed in indoor and out- door environments, on utility poles, and other urban structures. The sites can be located in private or public locations. Depending on the use case, each small-cell site has specific requirements for power sourcing, power budget, and backhaul transport. Meanwhile, the conventional macro-cell base stations will continue to increase network capacity, further driving demand for high-throughput backhaul. Wireless backhaul, emerged as a cost-effective connectivity option, has many advantages rela- tive to wired technologies, but wireless solutions also present unique design challenges among which are the need for spectrally efficient radio links, low operating power, small form factor, and environmentally resilient high-reliability equipment. RF analog integration also plays an important role. As an example, a typical microwave radio transmitter relies on RF analog inte- gration and RF building blocks to reduce the size, lower the power, and improve the dynamic performance. A wireless backhaul equipment requires four key components: antennas, radio transceiver, modem, and interface. The antenna transmits and receives electromagnetic waves. The radio transceiver handles RF carrier frequency transformation to and from the baseband. 5G Network Architecture 91 The modem performs channel coding/decoding and modulation/demodulation of the baseband signals, and the interface transports information between the radio and TDM/IP transport. As shown in Fig. 1.40, wired and wireless backhaul solutions employ broadband technologies that vary in terms of physical media and access method. Wired backhaul physical media include copper wire, hybrid fiber-coaxial (HFC)49 cable, and single-mode and multimode optical fiber. Transport access technologies are 