 cover the following main topics: Downlink physical channels and signals Uplink physical channels and signals Channel coding schemes Now, let's start with the downlink physical channels and signals. Downlink physical channels and signals NR defines a similar set of physical channels to Long-Term Evolution (LTE). We already covered the PSS, SSS, and PBCH. In this section, we will cover the Physical Downlink Control Channel (PDCCH), the Physical Downlink Shared Channel (PDSCH), as well as the Channel State Information Reference Signal (CSI-RS). The Tracking Reference Signal (TRS) and Phase Tracking Reference Signal (PTRS) are new reference signals that have been introduced in NR - we will see what they are used for. Let's learn about the PDCCH. 5G Air Interface and Physical Layer Procedures - Part 3 The PDCCH In NR, the PDCCH carries the Downlink Control Information (DCI), like LTE. The modulation used for the channel is Quadrature Phase Shift Keying (QPSK) and the Radio Network Temporary Identifier (RNTI) masks the DCI Cyclic Redundancy Check (CRC) bits as it was done in LTE. The PDCCH is divided into Control Channel Elements (CCEs) in NR. Each CCE is composed of six Resource Element Groups (REGs), where each REG is composed of one Physical Resource Block (PRB) in one Orthogonal Frequency Division Multiplexing (OFDM) symbol. The PDCCH is encoded in several CCEs depending on the aggregation level used. The PDCCH uses a one-port transmit diversity scheme in which the REG bundling is applied per CCE. The device can assume that the same precoder is applied to a set of REGs within a REG bundle. PDCCH CORESETs The set of resources to which a PDCCH can be mapped is called a Control Resource Set (CORESET). It is equivalent to the control region in LTE. A CORESET contains a set of REGs, and it is configured by the network using Radio Resource Control (RRC) signaling. CORESET #4 CORESET #3 CORESET #2 CORESET #1 one slot Figure 6.1 - A PDCCH CORESET The CORESET configuration consists of the frequency domain resources to use 