Remote Radio Head-RRH
Remote Radio head has become very important subsystems for distributed Base station Architecture. The remote radio head contains the base station's RF circuitry plus analog-to-digital or digital-to-analog converters and up/down converters.
RRH has operation and management functions. It has optical interface,which connects RRH with base station system.
RRH Base station system consists of REC and RE,
where in REC consists of baseband processing chain viz.
scrambling, channel coding and modulation. RE consists of ADC/DAC, PA, LNA and RF/IF
filters. Distance between REC and RE will be usually about 10Km and interface will
be optical signal which usually carry Control/mgmt, Sync and IQ signals.
RRH is used to extend the coverage of a base station sub-systems in the remote rural areas.
The main funtions of development of RRH(Remote Radio Head) are as follows:
1. Offload IF and RF processing from base station.
2. Increase in distance between RF antenna and Base Station Hardware.
3. Use of cheap optical fibre to carry data between RRH and Base Station Controller.
RRH incorporates following complex functionalities. In order to have complex funtionalities FPGAs are
used in the design of RRH.
• Digital Up Conversion(DUC)
• Digital Down Conversion(DDC)
• Crest Factor Reduction(CFR)
• Digital Pre-distortion(DPD)
RRH(Remote Radio Head) supports multiple wireless standards/technologies. The CPRI speficification V4.2 defines support for UMTS, WiMAX and E-UTRA standards in the RRH design.
Control and Mgmt- Used for call processing and for operation and maintenance signals.
Sync- Used for synchronization purpose, will carry timing information.
IQ- Data that will be carried between radio base station to the mobile station and vice versa.
Above RRH interfaces are connected with Layer 2. Layer 2 is connected with layer 1 i.e. PHY layer.
Common Public Radio Interface-CPRI Specification V1.4 for RRH,