igh bearer to new proto- cols and technology developments. Despite the rapid improvements in line speeds, port densities, and performance, the network control plane mechanisms have advanced at a much slower pace. Thus, with the adoption of SDN, the network becomes more programmable and agile. While SDN covers the revolution of routers and switches in the network, NFV handles other boxes in the network that performs more complex packet processing. NFV calls for the virtualization of net- work functions (NFs) currently provided by legacy middleboxes and gateways. Using virtualization and cloud technologies, NFV allows legacy NFs offered by specialized equipment to run in software on generic hardware. It makes it possible to deploy virtualized network functions in high-performance commodity servers of operator's data center, with the great flexibility to spin on/off the services on demand. Thanks to their promising benefits in flexibility and cost savings, today, both the wireline and wireless cellular networks have shifted to virtualization and cloud technologies, from both research and industry point of view. With the fast-growing traffic demand, the next-generation cellular network, that is, 5G cellular communications system, has heavily replied on the cloud technologies, NFV, and SDN. The 5G cellular network is expected to be commercialized by 2020. These technologies have been expected to impact different parts of cellular networks ranging from radio access network (RAN) all the way to the core network. The main motivation for offering this book stems from the obser- vation that, at present there is no systematic source of information about the cloud technologies' usage in the cellular network, as well as the interplay of different technologies, the discussion of different design choices, and its impact on our future cellular network. In addi- tion to providing the latest advances in this area, we also discuss sev- eral research topics that have been studied in the academic in these fields. By bringing the basi