A new distributed architecture called Cloud Radio Access Network (C-RAN) offers a new paradigm in base stations architecture that aims to reduce the number of cell sites while increasing the base station deployment density.
This new architecture breaks down the base station into a Base Unit (BU) – a digital unit that implements the MAC PHY and AAS (Antenna Array System) functionality, and the Remote Radio Head (RRH) that obtains the digital (optical) signals, converts digital signals to analog, amplifies the power, and sends the actual transmission. By making the RRH an active unit capable of converting from analog to digital, operators can now place numerous BUs in a single geographical point while distributing the RRUs according to the RF plans. The RRH becomes an intelligent antenna array which not only submits RF signals but also handles the conversion between digital and modular data. New RRH can also support multiple cellular generation (2G, 3G and LTE) eliminating the need for multiple antennas.
The C-RAN concept lowers operating expenses and simplifies the deployment process. By centralizing all the active electronics of multiple cell sites, at one location (aka the “Base Station Hotel”), energy, real-estate and security costs are minimized. The RRH can be mounted outdoor or indoor – on poles, sides of buildings or anywhere a power and a broadband connection exist, making installation less costly and easier. The RRH is typically connected using fiber to the BU, creating cloud-like radio access network topology. This topology saves costs both during the installation and later in the on-going operation.
The C-RAN architecture poses unique requirements to backhaul a “base station hotel” containing multiple base stations in order to connect them to the different controller sites.
The requirements:
- Multiple 1Gig connection
- Multiple 10Gig uplinks from the “base station hotel”
- Resiliency and fast recovery
- Synchronization schemes
- Strong QoS
- Strong OAM and service management
