A question may arise that if there are no wideband cell-specific reference signals, how the UEs will measure the reference signal received power (RSRP) during initial access or cell selection (mobility measurements) as they will not have any allocation at that time? The answer lies in the fact that NR uses a primary synchronization signal (PSS)/secondary syn- chronization signal (SSS)/PBCH block structure, where the PBCH has its own set of refer- ence signals which will always be present in the PBCH SO the UE while detecting the PSS/ SSS/PBCH block should be able to measure an RSRP value from the PBCH DM-RS. To support channel tracking, different types of reference signals are transmitted in downlink and uplink. The reference signals in the downlink include the following [6]: UE-specific DM-RS for physical downlink control channel (PDCCH) can be used for downlink channel estimation and coherent demodulation of PDCCH. The DM-RS for PDCCH is transmitted together with the PDCCH and is present only in the resource blocks that are used for PDCCH transmission. 416 Chapter 4 UE-specific DM-RS for physical downlink shared channel (PDSCH) can be used for downlink channel estimation for coherent demodulation of PDSCH. The DM-RS for PDSCH is transmitted together with the PDSCH and is present only in the resource blocks that are allocated for PDSCH transmission. UE-specific PT-RS can be used in addition to the DM-RS for PDSCH for correcting common phase error (CPE) between PDSCH symbols not containing DM-RS. It may also be used for Doppler and time-varying channel tracking. The phase noise of the transmitters increases as the frequency of operation increases. The PT-RS plays a crucial role especially in mmWave frequencies to minimize the effect of the oscillator phase noise on system performance. The phase noise appears as a common phase rotation of all the subcarriers, known as CPE in an OFDM system. The NR system typically maps the PT-RS information to a few subcarriers per symbol because the phase rotation equally affects