- For the control channel, the radio signaling, the Resource Block is not the adapted unit.
- The control channels mapped on the Resource Elements Groups (REGs), which represent less radio resources
- A REG is made up of 4 (or 6 if there are pilot sub-carriers) sub-carriers during 1 symbol.
- The REG are grouped into the CCE (Control Channel Element)
Resource element groups are sued for defining the mapping of control channels to resource elements.