LTE provides logical channels (which are defined by the type of information that they carry), that are mapped to transport channels and from there to physical channels (which are defined by their physical properties, i.e., time, subcarrier, etc.). The logical channels are similar to those in WCDMA

1. Traffic channels

• Dedicated Traffic CHannel (DTCH): It carries the user data for all ULs, as well as for those downlink data that are not multicast/broadcast.
• Multicast Traffic CHannel (MTCH): It carries the user data for multicast/broadcast downlink transmission.

2. Control channels

• Broadcast Control CHannel (BCCH): It carries system information data that are broadcast to the MSs in a cell. Note the difference from the MTCH, which also broadcasts to MSs, but carries user data.
• Paging Control CHannel (PCCH): It pages MSs in multiple cells (i.e., when it is not known exactly in which cell the MS currently is located).
• Common Control CHannel (CCCH): It transmits control data for the Random Access (RA), i.e., when a connection is started.
• Dedicated Control CHannel (DCCH): It is used for the transmission of control information that relates to a specific MS (as opposed to the system information relevant for all MSs, which is broadcast in the BCCH).
• Multicast Control CHannel (MCCH): It carries the control information related to multicast/broadcast services

These channels are mapped onto the following transport channels:

• Broadcast Channel (BCH): It carries part of the BCCH (the remainder is on the DL-SCH described below). It has a fixed format, so that any MS can listen to it easily.
• Paging Channel (PCH): It carries the PCCH.
• Multicast Channel (MCH): It is used to support broadcast/multicast transmission. It has a semistatic scheduling and transport format.

DownLink Shared Channel (DL-SCH) and UpLink Shared Channel (UL-SCH): they carry the user data, as well as most of the control information (except the one already mentioned above).

The data on transport channels are organized into transport blocks; in each transmission time interval (usually a subframe), one transport block is transmitted. A transport format is associated with each transport block. Finally, these transport channels are mapped onto physical channels; there are also physical channels that do not carry any transport channel, but are purely used for PHY functionality.

Downlink

• Physical Broadcast CHannel (PBCH ): It carries the BCH.
• Physical Downlink Shared CHannel (PDSCH ): It carries the DL-SCH, i.e., user data, some control data for the downlink, as well as the PCH.
• Physical Multicast CHannel (PMCH): It carries the MCH, which contains the multicast payload, as well as some of the control information for multicast.
• Physical Downlink Control CHannel (PDCCH ): It carries control information, such as scheduling that is required for reception of the PDSCH. This channel does not carry any transport channel.
• Physical Control Format Indicator CHannel (PCFICH ): It carries control information about the PDCCH. This channel does not carry any transport channel.
• Physical HARQ Indicator CHannel (PHICH ): It carries the feedback bits indicating whether a retransmission of transport blocks is necessary. This channel does not carry any transport channel.
• Synchronization Signal (SS ).

Uplink

• Physical Uplink Shared Channel (PUSCH): It is the uplink counterpart to the PDSCH.
• Physical Uplink Control Channel (PUCCH): It carries mainly three types of information: (i) channel state feedback, (ii) resource requests (remember that the BS performs the scheduling, i.e., assigns all the resources also for the uplink; thus the MS must request resources when it has data to transmit), and (iii) HARQ feedback bits.

• Physical Random Access CHannel (PRACH): It is used for the random access, i.e., MS communicating to the BS before a connection with scheduling has been established.