WHAT AVAILABLE LOGICAL CHANNELS EXIST IN LTE ?

Logical channels carry the type of information. In this regard, logical channels can be divided into control channels and traffic channels. The control channels are used for transfer of control plane information and the traffic channels are used for the transfer of user plane information.

The logical channels in LTE Air Interface are shown in the figure below.

Looking at the picture above, the following logical channels are supported for LTE:

Logical Control Channels

Broadcast Control Channel (BCCH): A downlink logical channel for broadcasting system control information.

Paging Control Channel (PCCH): A downlink logical channel that transfers paging information. This channel is used when the network wants to know which cell the UE is camped on at a given moment.

Common Control Channel (CCCH): This channel is used by the UEs having no RRC connection with the network. CCCH is used by the UEs when accessing a new cell or after cell reselection.

Multicast Control Channel (MCCH): A point-to-multipoint downlink channel used for transmitting multimedia broadcast and multicast system (MBMS) scheduling and control information from the network to the UE, for one or several Multicast Traffic channels (MTCHs). After establishing an RRC connection this channel is only used by UEs that receive MBMS.

Dedicated Control Channel (DCCH): A point-to-point bi-directional channel that transmits dedicated control information between a UE and the network. Used by UEs having an RRC connection.

Traffic Channels

Dedicated Traffic Channel (DTCH): A Dedicated Traffic Channel (DTCH) is a point-to-point channel dedicated to one UE for the transfer of user information. A DTCH can exist in both uplink and downlink.

Multicast Traffic Channel (MTCH): A point-to-multipoint downlink channel for transmitting traffic data from the network to the UEs using MBMS