Section: 5.5 Transport Channels
Content: The physical layer offers information transfer services to MAC and higher layers. The physical layer transport services are described by how and with what characteristics data are transferred over the radio interface. An adequate term for this is "Transport Channel". This should be clearly separated from the classification of what is transported, which relates to the concept of logical channels at MAC sublayer. Downlink transport channel types are: 1. Broadcast Channel (BCH) characterised by: - fixed, pre-defined transport format; - requirement to be broadcast in the entire coverage area of the cell, either as a single message or by beamforming different BCH instances. 2. 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. 3. 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, either as a single message or by beamforming different BCH instances; - mapped to physical resources which can be used dynamically also for traffic/other control channels. Uplink transport channel types are: 1. Uplink Shared Channel (UL-SCH) characterised by: - possibility to use beamforming; - 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. 2. Random Access Channel(s) (RACH) characterised by: - limited control information; - collision risk. Sidelink transport channel types are: 1. Sidelink broadcast channel (SL-BCH) characterised by: - pre-defined transport format. 2. Sidelink shared channel (SL-SCH) characterised by: - support for unicast transmission, groupcast transmission and broadcast transmission; - support for both UE autonomous resource selection and scheduled resource allocation by NG-RAN; - support for both dynamic and semi-static resource allocation when UE is allocated resources by the NG-RAN; - support for HARQ; - support for dynamic link adaptation by varying the transmit power, modulation and coding; - support for SL discontinuous reception (SL DRX) to enable UE power saving. Association of transport channels to physical channels is described in TS 38.202[ NR; Services provided by the physical layer ]  [20].