on general-purpose processors, whereas the service that requires simple user-data proces- sing can be processed on low-cost hardware platforms. It is obvious that enabling future expansions requires greater flexibility in the way that the networks are built. While net- work slicing is a key enabler to achieving greater flexibility, increasing flexibility may lead to greater complexity at all levels of the system, which in turn tends to increase the cost of operation and delay the deployments. 5G Network Architecture 7 Traditional radio access network (RAN) architectures consist of several stand-alone base stations, each covering relatively a small area. Each base station processes and trans- mits/receives its own signal to/from the mobile terminals in its coverage area and for- wards the user data payloads from the mobile terminal to the core network via a dedicated backhaul link. Owing to the limited spectral resources, network operators reuse the frequency among different base stations, which can cause interference among neigh- boring cells. There are several limitations in the traditional cellular architecture, including the cost and the operation and maintenance of the individual base stations; increased inter-cell interfer- ence level due to proximity of the other base stations used to increase network capacity; and variation of the amount of loading and user traffic across different base stations. As a result, the average utilization rate of individual base stations is very low since the radio resources cannot be shared among different base stations. Therefore, all base stations are designed to handle the maximum traffic and not the average traffic, resulting in over- provisioning of radio resources and increasing power consumption at idle times. In earlier generations of cellular networks, the macro-base stations used an all-in-one archi- tecture, that is, analog circuitry and digital processing hardware were physically co-located. The radio frequency (RF) signal generated by the base station transported o