RAN = the Radio Access Network
What is RAN? The part of a telecommunications system that implements a radio technology (e.g. UTRA, Evolved UTRA, CDMA2000, DECT, GERAN) to access the Core Network. The radio access network conceptually resides between user equipment (i.e. mobile phones and other devices) and the Core Network. Mavenir's cloud-based version is Virtualized RAN.
RRH = the actual Remote Radio Head
What is RRH? Radios placed on top of roof tops or towers. These are the core parts of the macroCell and Small cell transmission technology. As an MEC application, Private LTE is considered a small cell. In wireless system technologies such as GSM, CDMA, UMTS, LTE the radio equipment is remote to the BTS/NodeB/eNodeB. The equipment is used to extend the coverage of a BTS/NodeB/eNodeB in challenging environments such as rural areas or tunnels. They are generally connected to the BTS/NodeB/eNodeB via a fiber optic cable using Common Public Radio Interface protocols.
RRU = the actual Remote Radio Unit
What is RRU? A remote radio transceiver that connects to an operator radio control panel. Is used interchangeably with RRH (remote radio head), with RRH being the more common of the two. RRHs have become one of the most important subsystems of today's new distributed base stations. The RRH contains the base station's RF circuitry plus analog-to-digital/digital-to-analog converters and up/down converters.