The Full Form of RRH is Remote radio head.

A Remote Radio Head (RRH) or Remote radio unit (RRU) is the RF circuitry of a base station enclosed in a small outdoor module. The RRH performs all RF functionality like transmit and receive functions, filtering, and amplification. It also contains analog-to-digital or digital-to-analog converters and up/down converters. An RRH can also provide advanced monitoring and control features that allow operators to optimize performance from a remote, centralized location.

The RRH is usually mounted near the antenna to reduce transmission line losses and is connected to the main, digital portion of the base station (BBU) with an optical fiber. 

Common Public Radio Interface, or CPRI is the standardized protocol for communication between the BBU (Base Band Unit) and RRH, developed jointly by major RRH manufacturers. 

Open Base Station Architecture Initiative, or OBSAI is another standard developed by Hyundai, Nokia, Samsung, and ZTE in 2002 to create an open market for standardized base station functional blocks like the Remote Radio Head.