In order to send and receive data across the radio air interface and between different protocols, various channels are being used. The channels are used to distinguish the kind of data and to transport them across the radio access network. Different channels provide interfaces to the higher layers of the LTE protocol stack and enables an orderly and defined segregation of the data.

There are three types of channels into which the various data channels are grouped.

  • Physical channels: The physical channels carry control plane and user plane information over the air.

  • Transport channels: The transport channels offer information transfer to Medium Access Control (MAC) and higher layers.

  • Logical channels: The logical channels provide data transfer services for the MAC layer.

1. Logical Channels: 

Control and user plane data are carried on logical channels between the RLC and MAC layer. Logical channels can be classified into:

  • Control channels -  used for the transfer of control plane information only. 

  • Traffic channels - used for the transfer of user plane information only.

LTE Channels

1.1 Logical Control Channels:

  • Paging Control Channel (PCCH) - used for paging the UE

  • Broadcast Control Channel (BCCH) - used for broadcasting MIBs/SIBs

  • Common Control Channel (CCCH) - common to multiple UE's

  • Dedicated Control Channel (DCCH) - used to transmit dedicated control information for a particular UE

  • Multicast Control Channel (MCCH) - used for transmit information for Multicast reception

1.2 Logical Traffic Channels:

  • Dedicated Traffic Channel (DTCH) - used for dedicated traffic for a particular UE

  • Multicast Traffic Channel (MTCH) - used to transmit Multicast data

2. Transport Channels:

Control and user plane data are carried on transport channels between the MAC and physical layer.

2.1 Downlink Transport Channels:

  • Paging Channel (PCH) - used for paging

  • Broadcast Channel (BCH) - used for MIB, get mapped to BCCH

  • Downlink Shared Channel (DL-SCH) - used for SIB, data transfer

  • Multicast Channel (MCH) - used for transmitting MCCH information to set up multicast transmissions

2.2 Uplink Transport Channels:

  • Random Access Channel (RACH) - used for the initial access to the network (RANDOM ACCESS Procedure)

  • Uplink Shared Channel (UL-SCH) - used for UL data transfer

 

3. Physical Channels:

Control and user plane data are carried on physical channels between the different levels of the physical layer.

3.1 Downlink Physical Channels:

  • Physical Broadcast Channel (PBCH) - used for transmitting MIB

  • Physical Downlink Shared Channel (PDSCH) - for SIB, data

  • Physical Multicast Channel (PMCH) - multicast channel

  • Physical Hybrid ARQ Indicator Channel (PHICH) - for HARQ ack/nack status

  • Physical Downlink Control Channel (PDCCH) - control channel (carries information to UE about the scheduling of PDSCH), UL grant, Indication for paging, carries HARQ ACK/NACK

3.2 Uplink Physical Channels:

  • Physical Random Access Channel (PRACH) - contention channel used for transmission of random access preambles

  • Physical Uplink Shared Channel (PUSCH) - carries UL control and user information

  • Physical Uplink Control Channel (PUCCH) - carries UL control information (SRs, HARQ, CQ)