th at UE1 Signal strength at UE2 Figure 4.33 Example beam sweeping and correspondence to the transmission of SS burst set [30]. 486 Chapter 4 time-division multiplexing beam-sweeping allows for low-cost analog antenna array archi- tectures. Frequency-division multiplexing is another approach that could have been poten- tially adopted in NR; however, it would have precluded use of analog antenna array architectures. This feature, although particularly useful for mmWave operation, can also be leveraged at lower frequency bands. In LTE, the PSS/SSS and PBCH are always located at the center of the RF carrier. Thus once an LTE device detects the PSS/SSS, it has already found the center frequency of the carrier. The drawback of this approach is that a device with no a priori knowledge of the frequency-domain carrier position must search for PSS/SSS at all possible carrier positions. To allow a faster cell search in NR, the possible SS block locations for each frequency band are a limited set of frequencies referred to as the synchronization raster. Therefore, instead of searching for an SS block at each carrier raster, a UE only needs to search for an SS block within the sparse set of synchronization raster. Since NR carriers can still be located at an arbitrary position on the carrier raster, the SS block may not be necessarily located at the center of a carrier, and it may not be aligned with the resource block grid due to different numerologies. Thus once the SS block has been detected, the device must be explicitly informed about the exact SS block frequency-domain position on the carrier. This is achieved by means of information partly within PBCH and partly within the RMSI. As we mentioned earlier, an SS/PBCH block consists of four OFDM symbols in the time domain, numbered in increasing order from 0 to 3 within the SS/PBCH block, where PSS, SSS, and PBCH with the associated DM-RS are mapped to symbols as shown in Fig. 4.29. In the frequency domain, an SS/PBCH block consists of 240 contiguous subcarriers with the 