The fifth generation (5G) technology improves the user experience and creates new possibilities for a variety of applications, including transportation, device-to-device communication, agriculture, and manufacturing. These new use-cases significantly increase the number of users, volume of traffic, throughput, and latency. Hence, there is a need to modify the radio access network (RAN) for the 5G system. This study investigates the various RAN architectures such as cloud-RAN (CRAN), heterogeneous cloud-RAN (HCRAN), and fog-RAN (FRAN). The architectures are examined in a variety of contexts, including system efficiency, spectrum and energy efficiency, fronthaul capacity, latency, resource sharing and allocation, and so on. Also, current issues with these architectures are highlighted, as well as some existing remedies.