LTE - Physical Channel, Transort Channel and Logical Channel Overview

LTE - Physical Channel, Transort Channel and Logical Channel Overview (Daniel Hu Study Note)










Channel List (doc)

The physical DL channels of E-UTRA are:
Physical broadcast channel (PBCH)
- The coded BCH transport block is mapped to four subframes within a 40 ms interval;
- 40 ms timing is blindly detected, i.e. there is no explicit signalling indicating 40 ms timing;
- Each subframe is assumed to be self-decodable, i.e. the BCH can be decoded from a single reception, assuming sufficiently good channel conditions.
Physical control format indicator channel (PCFICH)
- Informs the UE about the number of OFDM symbols used for the PDCCHs;
- Transmitted in every subframe.
Physical downlink control channel (PDCCH)
- Informs the UE about the resource allocation of PCH and DL-SCH, and Hybrid ARQ information related to DL-SCH;
- Carries the uplink scheduling grant.
Physical downlink shared channel (PDSCH)
- Carries the DL-SCH and PCH.
Physical multicast channel (PMCH)

The physical UL channels of E-UTRA are:
Physical uplink control channel (PUCCH)
- Carries Hybrid ARQ ACK/NAKs in response to downlink transmission;
- Carries Scheduling Request (SR);
- Carries CQI reports.
Physical uplink shared channel (PUSCH)
- Carries the UL-SCH.
Physical Hybrid ARQ Indicator Channel (PHICH)
- Carries Hybrid ARQ ACK/NAKs in response to uplink transmissions.
Physical random access channel (PRACH)
- Carries the random access preamble.

The transport DL channels of E-UTRA
Broadcast Channel (BCH) characterised by:
- fixed, pre-defined transport format;
- requirement to be broadcast in the entire coverage area of the cell.
Downlink Shared Channel (DL-SCH) characterised by:
- support for HARQ;
- support for dynamic link adaptation by varying the modulation, coding and transmit power;
- possibility to be broadcast in the entire cell;
- possibility to use beamforming;
- support for both dynamic and semi-static resource allocation;
- support for UE discontinuous reception (DRX) to enable UE power saving;
- support for MBMS transmission.
NOTE: the possibility to use slow power control depends on the physical layer.
Paging Channel (PCH) characterised by:
- support for UE discontinuous reception (DRX) to enable UE power saving (DRX cycle is indicated by the network to the UE);
- requirement to be broadcast in the entire coverage area of the cell;
- mapped to physical resources which can be used dynamically also for traffic/other control channels.
Multicast Channel (MCH) characterised by:
- requirement to be broadcast in the entire coverage area of the cell;
- support for MBSFN combining of MBMS transmission on multiple cells;
- support for semi-static resource allocation e.g. with a time frame of a long cyclic prefix.

The transport UL channels of E-UTRA are:
Uplink Shared Channel (UL-SCH) characterised by:
- possibility to use beamforming; (likely no impact on specifications)
- support for dynamic link adaptation by varying the transmit power and potentially modulation and coding;
- support for HARQ;
- support for both dynamic and semi-static resource allocation.
NOTE: the possibility to use uplink synchronisation and timing advance depend on the physical layer.
Random Access Channel(s) (RACH) characterised by:
- limited control information;
- collision risk;
NOTE: the possibility to use open loop power control depends on the physical layer solution

The logical control channels of E-UTRA :
Control Channels
Control channels are used for transfer of control plane information only. The control channels offered by MAC are:
Broadcast Control Channel (BCCH)
- A downlink channel for broadcasting system control information.
Paging Control Channel (PCCH)
A downlink channel that transfers paging information and system information change notifications. This channel is used for paging when the network does not know the location cell of the UE.
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 MBMS.
NOTE: is FFS how MBMS scheduling is transmitted by either L2/3 signalling on MCCH or L1 signalling.
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.

The logical traffic channels of E-UTRA :
Traffic Channels
Traffic channels are used for the transfer of user plane information only. The traffic channels offered by MAC are:
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)

For Further Information:
http://docs.google.com/fileview?id=F.d8bbc727-e881-4859-9bd7-cde24186c3bd