Channels and the Protocol Stack of UMTS

Channels and the Protocol Stack of UMTS

• The mapping between Logical and Transport channels is performed by the LAC layer
• The mapping between Transport and Physical channels is performed by the Physical layer

The below we detail about Logical Channel
1/ W-CDMA Logical Channels
BCHBroadcast Channel Carries system and cell-specific information; always transmitted over the entire cell with a low fixed bit rate.
FACHForward Access Channel
- Carries control information from base station to mobile in one cell when the system knows the location cell of the mobile.
- May also carry short user packets.
- May be transmitted over whole cell or over a portion using lobe-forming antennas.
PCHPaging Channel For messages to the mobiles in the paging area
RACHRandom Access Channel
- Uplink channel used to carry control information from the UE
- May also carry short user packets
- Always received from the entire cell
CPCHCommon Packet Channel
- Carries small and medium-sized packets
- A contention-based, random access channel used for transmission of bursty data traffic
- Associated with a dedicated channel on the downlink, which provides power control for the uplink CPCH
DCHDedicated Channel
- A downlink or uplink channel used to carry user or control information between the network and the UE
- Corresponds to three channels:

• DTCH Dedicated Traffic Channel
• SDCCH Stand-Alone Dedicated Control Channel
• ACCH Associated Control Channel

- Transmitted over the whole cell or only a part using lobe-forming antennas
- May have fast rate changes (even every 10 ms), and fast power control

Related to W-CDMA Transport Channels