What is RRH (Remote Radio Head), How it is connected to BBU (Base Band Unit) ?

LTE, RF Basics, Tech Fundas

The remote radio head (RRH) contains the base station’s RF circuitry plus analog-to-digital or digital-to-analog converters and up/down converters.

It is sitting on top of cell tower that mainly performs following functions:

  • Convert optical signal to electrical signal and vice versa using CPRI
  • In transmitter section of RRH, it convert digital signal to RF and amplifies that signal to the desire power level and Antenna connected to it, radiates the RF signal in air
  • In Receiver section of RRH, it receives the desired band of signal from antenna and amplify it.
  • And convert RF signal back to digital signal in the receiver chain.

RRH has been made of RF transmitter chain and RF receiver chain which includes the ADC (Analog to digital converter), DAC (Digital to analog converter), Mixer, PA (Power amplifier), LNA (Low Noise Amplifier) etc. Basic Block diagram of RRH is as shown below:

RRH is connected to the Base band unit (BBU) via optical cable. Optical cable is used because it has less loss and it is cheaper as compared to RF Coaxial cable.

One base-band unit is connected to multiple RRHs depending upon the capability of base-band unit.