Editing My 3GPP 38.300 Notes (section)

== 5.2 Downlink ==

=== 5.2.5 Physical layer procedures ===

==== 5.2.5.1	Link adaptation ====
Link adaptation (AMC: adaptive modulation and coding) with various modulation schemes and channel coding rates is applied to the PDSCH. The same coding and modulation is applied to all groups of resource blocks belonging to the same L2 PDU scheduled to one user within one transmission duration and within a MIMO codeword.

For channel state estimation purposes, the UE may be configured to measure CSI-RS and estimate the downlink channel state based on the CSI-RS measurements. The UE feeds the estimated channel state back to the gNB to be used in link adaptation.

==== 5.2.5.2 Power Control ====
Downlink power control can be used.

==== 5.2.5.3 Cell search ====
<span style="color:red">Cell search is the procedure by which a UE acquires time and frequency synchronization with a cell and detects the Cell ID of that cell. NR cell search is based on the primary and secondary synchronization signals, and Physical Broadcast Channel (PBCH) Demodulation Reference Signal (DMRS), located on the synchronization raster.</span>

==== 5.2.5.4 HARQ ====
Asynchronous Incremental Redundancy Hybrid Automatic Repeat ReQuest (ARQ), or HARQ, is supported. The gNB provides the UE with the HARQ-ACK feedback timing either dynamically in the Downlink Control Information (DCI) or semi-statically in an Radio Resource Controller (RRC) configuration. Retransmission of HARQ-ACK feedback is supported by using enhanced dynamic codebook and/or one-shot triggering of HARQ-ACK transmission for (i) all configured CCs and HARQ processes in the Physical Uplink Control Channel (PUCCH) group, (ii) a configured subset of CCs and/or HARQ processes in the PUCCH group, or (iii) a dynamically indicated HARQ-ACK feedback instance. For HARQ-ACK of Semi-Persistent Scheduling (SPS) Physical Downlink Shared Channel (PDSCH) without associated PDCCH, in case of HARQ-ACK dropping due to Time Division Duplexing (TDD) specific collisions, the HARQ-ACK feedback can be deferred to a next available PUCCH transmission occasion.

The UE may be configured to receive code block group based transmissions where retransmissions may be scheduled to carry a sub-set of all the code blocks of a Transport Block (TB).

==== 5.2.5.5 Reception of SIB1 ====

The Master Information Block (MIB) on Physical Broadcast Channel (PBCH) provides the UE with parameters (e.g. CORESET#0 configuration) for monitoring of PDCCH for scheduling PDSCH that carries the System Information Block 1 (SIB1). PBCH may also indicate that there is no associated SIB1, in which case the UE may be pointed to another frequency from where to search for an Synchronization Signal (SS)/Physical Broadcast Channel (PBCH) block (SSB) that is associated with a SIB1 as well as a frequency range where the UE may assume no SSB associated with SIB1 is present. The indicated frequency range is confined within a contiguous spectrum allocation of the same operator in which SSB is detected.