SDCCH (Stand-alone Dedicated Control Channel)
- Uplink and Downlink.
- Used for call setup, authentication, ciphering location update and SMS.
SACCH (Slow Associated Control Channel)
- Downlink and Uplink.
- Used to transfer signal while MS have ongoing conversation on traffic or while SDCCH is being used.
- On the forward link, the SACCH is used to send slow but regularly changing control information to each mobile on that ARFCN, such as power control instructions and specific timing advance instructions
- The reverse SACCH carries information about the received signal strength and quality of the TCH, as well as BCH measurement results from neighboring cells.
FACCH (Fast Associated Control Channel)
- Downlink and uplink.
- Associate with TCH only.
- It is used to send fast message like hand over message.
- Work by stealing traffic bursts.