In radio networks, the radio modules are normally housed in the rack of the radio base station. From there, the RF signals are forwarded to the antenna via low- loss radio frequency cables. In contrast to this concept, RRH (Remote Radio Head) systems relocate the radio module to the antenna and connect it to the baseband unit ( BBU) via a lossless digital transmission link using fiber to the antenna( FTTA).
The advantage of the RRH concept is that the digital transmission path is lossless, which means that the lack of cable attenuation of the coaxial cable benefits the transmission level. Depending on the transmission frequency, this may well be 3 dB and higher. The RRH concept provides for networking of several radio modules via a digital link, with which greater coverage is then achieved.
The Common Public Radio Interface ( CPRI) and Open Base Station Architecture Initiative ( OBSAI) interface standards are available for connecting remote HF units. The RRH concept offers itself as an alternative to radiation techniques with adaptive antenna systems, Adaptive Antenna Systems( AAS), and Multiple Input Multiple Output( MIMO), which uses scatter propagation paths to optimize reception conditions.