LTE logical channels structure and mapping between logical channels and transport channels.
Logical channels reside between RLC sublayer and MAC sublayer which are layer 2 protocols in LTE protocol stack. Logical channels tells what kind of information is transferred. Logical channels can be broadly divided into two types:
- Control Channels (for the transfer of control plane information)
- Traffic Channels (for the transfer of user plane information)
Control channels are use for transferring control plane information. The different control channels in LTE are:
Broadcast Control Channel (BCCH)
BCCH channel is used for transferring system control information. Broadcast Control Channel (BCCH) is a downlink channel.
Paging Control Channel (PCCH)
PCCH is a downlink channel which carries paging information and system information change.
Common Control Channel (CCCH)
Channel for transmitting control information between UEs and network. This channel is used for UEs having no RRC connection with the network.
Multicast Control Channel (MCCH)
A point-to-multipoint downlink channel used for transmitting MBMS control information from the network to the UE, for one or several MTCHs. This channel is only used by UEs that receive or are interested to receive MBMS.
Dedicated Control Channel (DCCH)
DCCH is used when there is RRC Connection. DCCH transfers dedicated control information between UE and network. Dedicated Control Channel (DCCH) is a bidirectional channel.
Traffic channels are used to carry user plane information. There are two types of logical traffic channels available in LTE
Dedicated Traffic Channel (DTCH)
DTCH is a bi-directional channel used to transfer user plane information between UE and network.
Multicast Traffic Channel (MTCH)
A point-to-multipoint downlink channel for transmitting traffic data from the network to the UE. This channel is only used by UEs that receive MBMS.
Mapping between logical channels and transport channels
Mapping in uplink
Mapping in downlink