7.1.1        Overview of physical channels

A downlink physical channel corresponds to a set of resource elements carrying information originating from higher layers. The following downlink physical channels are defined:

-        Physical Downlink Shared Channel, PDSCH

-        Physical Broadcast Channel, PBCH

-        Physical Downlink Control Channel, PDCCH.

对下行物理通道进行一个概述，RE承载的数据来源于更高层L2或者L3，主要包含PDSCH，PBCH，PDCCH

7.1.2        Overview of physical signals

A downlink physical signal corresponds to a set of resource elements used by the physical layer but does not carry information originating from higher layers.

物理信号不承载更高层的数据，主要用于信道估计和同步使用，具体包含以下几种物理信号：

The following downlink physical signals are defined:

-        Demodulation reference signals, DM-RS

-        Phase-tracking reference signals, PT-RS

-        Positioning reference signal, PRS

-        Channel-state information reference signal, CSI-RS

-        Primary synchronization signal, PSS

-        Secondary synchronization signal, SSS

7.2        Physical resources

The following antenna ports are defined for the downlink:

-        Antenna ports starting with 1000 for PDSCH

-        Antenna ports starting with 2000 for PDCCH

-        Antenna ports starting with 3000 for channel-state information reference signals

-        Antenna ports starting with 4000 for SS/PBCH block transmission

-        Antenna ports starting with 5000 for positioning reference signals

该段指示了不同信号数据对应的天线端口

The UE shall not assume that two antenna ports are quasi co-located with respect to any QCL type unless specified otherwise.

 antenna ports：UE假定不同天线端口对应的信道H，相互独立，除非进行了特别说明

For DM-RS associated with a PDSCH, the channel over which a PDSCH symbol on one antenna port is conveyed can be inferred from the channel over which a DM-RS symbol on the same antenna port is conveyed only if the two symbols are within the same resource as the scheduled PDSCH, in the same slot, and in the same PRG as described in clause 5.1.2.3 of [6, TS 38.214].

For DM-RS associated with a PDCCH, the channel over which a PDCCH symbol on one antenna port is conveyed can be inferred from the channel over which a DM-RS symbol on the same antenna port is conveyed only if the two symbols are within resources for which the UE may assume the same precoding being used as described in clause 7.3.2.2.

For DM-RS associated with a PBCH, the channel over which a PBCH symbol on one antenna port is conveyed can be inferred from the channel over which a DM-RS symbol on the same antenna port is conveyed only if the two symbols are within a SS/PBCH block transmitted within the same slot, and with the same block index according to clause 7.4.3.1.

上述介绍了，DM-RS作为参考信号使用的条件，即有相同的天线号