BCH (Broadcast Channels)

BCCH(Broadcast Control Channels)

  • Downlink Only.
  • Broadcast information of the serving cell (System Information).
  • Transmitted on timeslot zero of BCCH carrier.
  • Read only by idle mobile at least once every 30 secs.

SCH (Synchronization Channels)

  • Downlink Only
  • Carries information for frame synchronization.
  • Contains frame number and BSIC (Base Station Identity Code).

FCCH (Frequency Correction Channels)

  • Downlink Only.
  • Enable MS to synchronize to the frequency.

CCCH (Common Control Channel)

RACH(Random Access Channel)

  • Uplink only.
  • Used by the MS when making its first access to the Network.
  • The reason for access could be initiation of a call or a page response.

AGCH (Access Grant Channel)

  • Downlink only.
  • Used for acknowledgement of the access attempt sent on RACH.
  • Used by the network to assign a signaling channel upon successful decoding of access bursts.

PCH (Paging Channel)

  • Downlink only.
  • The network will page the MS ,if there is a incoming call or a short Message.
  • It contains the MS identity number, the IMSI or TMSI.

DCCH (Dedicated Control Channel)

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.